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Tropical cyclone warnings and watches
Tropical cyclone warnings and watches
Tropical cyclone warnings and watches
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Alert issued for Hawaii about a hurricane warning during Hurricane Lane in 2018
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Tropical cyclone warnings and watches are alerts issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate preparation for the cyclone, including evacuation of vulnerable areas where necessary. It is important that interests throughout the area of an alert make preparations to protect life and property, and do not disregard it on the strength of the detailed forecast track.

Western Hemisphere

[edit]
See also: History of Atlantic hurricane warnings
Hurricane warning levels
Hurricane warning
Hurricane conditions
expected within 36 hours.
Hurricane watch
Hurricane conditions
possible within 48 hours.
Tropical storm warning
Tropical storm conditions expected within 36 hours.
Tropical storm watch
Tropical storm conditions possible within 48 hours.
Storm surge warning
Life-threatening storm surge possible within 36 hours.
Storm surge watch
Life-threatening storm surge possible within 48 hours.
Extreme wind warning
Winds reaching Category 3 status or higher likely (issued two hours or less before onset of extreme winds).

New tropical cyclone position and forecast information is available at least every twelve hours in the Southern Hemisphere and at least every six hours in the Northern Hemisphere from Regional Specialized Meteorological Centers and Tropical Cyclone Warning Centers.[1][2][3][4][5] In conjunction with the National Hurricane Center, the national meteorological and hydrological services of Central America, the northern Atlantic Ocean, and the northeastern Pacific Ocean east of the 140th meridian west, excluding mainland Africa and Europe, all issue tropical storm/hurricane watches and warnings.[6] Tropical storm watches are issued when gale and storm force winds of between 34 and 63 kn (39 and 72 mph; 63 and 117 km/h) are possible, within 48 hours in a specified area in association with a tropical, subtropical or post-tropical cyclone.[7] These watches are upgraded to tropical storm warnings, when gale and storm force winds become expected to occur somewhere in the warning area within 36 hours.[7] Hurricane watches are issued when sustained winds of 64 knots (74 mph; 119 km/h) are possible, within 48 hours in a specified area in association with a tropical, subtropical or post-tropical cyclone.[7] These watches are upgraded to hurricane warnings, when hurricane-force winds become expected to occur somewhere in the warning area within 36 hours.[7]

Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch and warnings are issued in advance of the anticipated onset of tropical-storm-force winds, rather than in advance of the anticipated onset of hurricane-force winds.[7] At times a tropical storm warning and a hurricane watch can both be in effect due to uncertainties in the forecast. These watches and warnings are also issued by the Central Pacific Hurricane Center for the Hawaiian Islands and the Weather Forecast Office in Guam for parts of Micronesia but not for American Samoa due to an international agreement.[8]

Within the United States, an extreme wind warning is issued by the National Weather Service for any land areas that are expected to be impacted by a major hurricane (Category 3 or higher) and by sustained surface winds greater than or equal to 100 kn (120 mph; 190 km/h).[8] The warning is issued just prior to when the strongest winds of the eyewall are expected to impact an area.[9] The warning is to be issued for the smallest area possible, and be valid for times of two hours or less.[9] It was developed in response to confusion resulting from the landfall of Hurricane Katrina. NWS offices in Jackson and New Orleans/Baton Rouge issued 11 tornado warnings for areas that would not experience an actual tornado, but would experience extreme wind speeds commonly associated with tornadoes.[10] The extreme wind warning is now expected to be used in these situations.

In 2017, the National Hurricane Center introduced a new system of warnings and watches for storm surge, which would cover the Atlantic and Gulf Coasts of the United States. A storm surge watch would be issued when a life-threatening storm surge, associated with a potential or ongoing tropical, subtropical or post-tropical cyclone, is possible within the next 48 hours. These watches would be upgraded to storm surge warnings when there is a danger of life-threatening storm surge occurring within 36 hours. However, both watches and warnings may be issued earlier than specified if environmental conditions are expected to hamper preparations.[11]

In Mexico, a color coded alert system is used to keep the public informed when a tropical cyclone or possible tropical cyclones poses a threat to the nation. The scale starts with blue at the bottom being minimal danger, then proceeds to a green alert, which means low level danger. A yellow alert signifies moderate danger, followed by an orange alert that means high danger level. The scale tops off with a red alert, the maximum level of danger.[12]

Canada

[edit]

In Canada, terminology is fairly similar to that of the United States, but there are a few differences:[13]

  • Watches are issued 36 hours prior to a tropical cyclone making landfall.
  • Warnings are issued 24 hours prior to the tropical cyclone making landfall.
  • If sustained winds 70 km/h and/or gusts 90 km/h or stronger are predicted, a conventional wind warning will be issued along with the tropical cyclone watches and warnings.
  • A storm surge warning may be issued if abnormally high water levels are predicted.

Western Pacific basin

[edit]

China

[edit]

A two-stage warning system was long-established in China for tropical cyclones of tropical storm intensity of above.[14] Nowadays, the use of this system is restricted to coastal waters only. Thus, warnings may be discontinued even if a cyclone is maintaining tropical storm intensity inland. Color-coded alerts (below) may be in effect independently of any two-stage warnings.

Later, China Meteorological Administration standardized the system for national use.[15] This set is part of a larger warning system that covers other forms of severe weather conditions, such as extreme temperature, torrential rainfall, drought, etc.

Level Name Sign Meaning
IV Blue typhoon alert
台风蓝色预警信号 		Within 24 hours, it may or may have been affected by tropical cyclones. The average wind power on the coast or land is above 6, or the gust above 8 and may continue.
III Yellow typhoon alert
台风黄色预警信号 		Within 24 hours, it may or may have been affected by tropical cyclones. The average wind power on the coast or land is above 8, or the gust above 10 and may continue.
II Orange typhoon alert
台风橙色预警信号 		Within 12 hours, it may or may have been affected by tropical cyclones. The average wind power on the coast or land is above 10, or the gust above 12 and may continue.
I Red typhoon alert
台风红色预警信号 		Within 6 hours, it may or may have been affected by tropical cyclones. The average wind power on the coast or land is above 12, or the gust above 14 and may continue.

Guangdong

[edit]

Guangdong continued to set up the White typhoon alert for typhoon, indicating that tropical cyclones may affect the area within 48 hours. In some inland areas that are less affected by tropical cyclones (such as Qinghai, etc.), there is no typhoon warning signal, but when it is hit by tropical cyclones, a strong wind warning signal will be issued. The winds represented by each color are consistent with the typhoon warning signal.

Typhoon warning signals used in Guangzhou from June 1, 1995, to November 1, 2000:[16]

Name Meaning
Windproof Info (Tropical Storm or Typhoon Info) indicates that a tropical storm or typhoon has entered the South China Sea (or has formed in the South China Sea) and is likely to move to the coastal areas of the province.
Windproof Warning (Tropical Storm and Typhoon Warning) Indicating that a tropical storm or typhoon warning enters the South China Sea, its route is moving in the direction of the Pearl River Estuary. If there is no change, it may land within 48 hours.
Windproof Special Alert (Tropical Storm or Typhoon Emergency Alert) Indicating that a tropical storm or typhoon hits the Pearl River Estuary within 24 hours, or landed in a coastal area within 150 kilometers of the Pearl River Estuary, which will have a serious impact on Guangzhou.
Disarming (Tropical Storm or Typhoon Disarming Alert) indicates that a tropical storm or typhoon has landed (or weakened to a low pressure).

Typhoon warning signals used from November 1, 2000, to May 2006:[17]

Name Signal Meaning
White typhoon alert Tropical cyclones may affect the area within 48 hours.
Green typhoon alert Tropical cyclones will be within 24 hours or are affecting the area, with an average wind level of strong winds (6–7) (41-62 km/h).
Yellow typhoon alert Tropical cyclones will be within 12 hours or are affecting the area, with an average winds level of strong gale (8–9) (63-87 km/h).
Red typhoon alert Tropical cyclones will be within 12 hours or are affecting the area, with an average winds level of strong storm (10–11) (88-117 km/h).
Black typhoon alert Tropical cyclones will be within 12 hours or are affecting the area, with an average winds level of typhoon (>12).

Typhoon warning signals used from June 1, 2006, to December 31, 2014:[18]

Name Signal Meaning
White typhoon alert Tropical cyclones may affect the area within 48 hours.
Blue typhoon alert It may be affected by tropical cyclones within 24 hours, the average wind power can reach above level 6, or gusts above 7; or it has been affected by tropical cyclones with an average wind power of 6–7, or gusts of 7–8, and may continue.
Yellow typhoon alert It may be affected by tropical cyclones within 24 hours, the average wind power can reach above level 8, or gusts above 9; or it has been affected by tropical cyclones with an average wind power of 8–9, or gusts of 9–10, and may continue.
Orange typhoon alert It may be affected by tropical cyclones within 12 hours, the average wind power can reach above level 10, or gusts above 11; or it has been affected by tropical cyclones with an average wind power of 10–11, or gusts of 11–12, and may continue.
Red typhoon alert It may be affected by tropical cyclones within 6 hours, the average wind power can reach above level 12; or it has been affected by tropical cyclones with an average wind power of 12, and may continue.

Typhoon warning signals used since January 1, 2015:[19]

Name Signal Meaning
White typhoon alert 2015版广东省突发气象灾害预警信号之台风预警信号 Tropical cyclones may affect the area within 48 hours.
Blue typhoon alert 2015版广东省突发气象灾害预警信号之台风预警信号 It may be affected by tropical cyclones within 24 hours, the average wind power can reach above level 6, or gusts above 7; or it has been affected by tropical cyclones with an average wind power of 6–7, or gusts of 7–8, and may continue.
Yellow typhoon alert 2015版广东省突发气象灾害预警信号之台风预警信号 It may be affected by tropical cyclones within 24 hours, the average wind power can reach above level 8, or gusts above 9; or it has been affected by tropical cyclones with an average wind power of 8–9, or gusts of 9–10, and may continue.
Orange typhoon alert 2015版广东省突发气象灾害预警信号之台风预警信号 It may be affected by tropical cyclones within 12 hours, the average wind power can reach above level 10, or gusts above 11; or it has been affected by tropical cyclones with an average wind power of 10–11, or gusts of 11–12, and may continue.
Red typhoon alert 2015版广东省突发气象灾害预警信号之台风预警信号 It may be affected by tropical cyclones within 6 hours, the average wind power can reach above level 12; or it has been affected by tropical cyclones with an average wind power of 12, and may continue.
Shenzhen
[edit]

Shenzhen currently uses a different signal from Guangdong Province:[18][20]

Zhuhai
[edit]

Zhuhai adopts the signal style of Guangdong Province, but the meaning of the signal is different:[21]

Ball signal

[edit]
Shenzhen and Zhuhai
[edit]

Shenzhen and Zhuhai used digitally arranged typhoon signals from June 4, 1994, to November 1, 2000,[22] but they have now been replaced by typhoon warning signals.

Ports
[edit]

The coastal ports of various cities in mainland China will still hang the squash signal when the typhoon hits.[23] The sign is roughly the same as the typhoon signal used in Shenzhen and Zhuhai.[24]

Hong Kong and Macau

[edit]
Main article: Hong Kong tropical cyclone warning signals

The Pearl River Delta uses a variety of warning systems to inform the public regarding the risks of tropical cyclones to the area.

The Hong Kong Observatory issues typhoon signals to indicate the existence and effects of a tropical cyclone on Hong Kong. The first numeric warning system was used in 1917.

The Macao Meteorological and Geophysical Bureau in Macau uses a similar system.[25]

In Hong Kong the typhoon signal system consists of 8 signals in 5 levels numbered non-consecutively for historical reasons.[26][27] Each signal has a day signal and a night signal for hoisting, which are still hoisted in Macau but no longer hoisted in Hong Kong. Day signals are also used as signal symbols in both places.

Signal Symbol in Hong Kong Symbol in Macau Night Signal in Macau Note Wind speed Gust
No.1 (Standby) A tropical cyclone is centred within 800 km of the territory. NA NA
No.3 A definite warning that a tropical cyclone is expected to come near enough to Hong Kong to cause strong winds in Hong Kong. It normally gives 12 hours warning of strong winds generally over Hong Kong at sea level, but in exposed areas, winds may become strong sooner.

Implication for citizens: Do not need to go to kindergartens, some places and events.

Strong wind with a sustained speed of 41–62 km/h ≥ 110 km/h
No.8. NW Gale or storm force wind.

4 different symbols for different directions.

Implication for citizens: Usually no need to go to school or work for most people if hosted before a certain hours before official work hours; depends on official announcement & employment contracts.

Sustained speed of 63–117 km/h from the northwest, southwest, northeast, southeast quadrants respectively ≥ 180 km/h.
No.8. SW
No.8. NE
No.8. SE
No. 9 (Hong Kong) Gale or storm force wind is increasing or expected to increase significantly in strength. / (Macau) The centre of a tropical cyclone is approaching and Macau is expected to be severely affected. It usually implies that wind speeds are expected to reach 88 to 117 kilometres per hour.
No. 10 Hurricane-force wind.
Implication for citizens: No need to go to work or school. Most public transportation stops. 		Winds range upwards from 118 kilometres per hour. ≥ 220 km/h

Japan

[edit]
Main article: Japan Meteorological Agency

The Japan Meteorological Agency (JMA) is the government agency responsible for gathering and providing results for the public in Japan, that are obtained from data based on daily scientific observation and research into natural phenomena in the fields of meteorology, hydrology, seismology and volcanology, among other related scientific fields. Its headquarters is located in Tokyo.

JMA is also designated one of the Regional Specialized Meteorological Centers (RSMC) of the World Meteorological Organization. It has the responsibility for weather forecasting, tropical cyclone naming and distribution of warnings for tropical cyclones in the Northwestern Pacific region.

Philippines

[edit]
Main article: Tropical Cyclone Wind Signals
PAGASA's
Tropical Cyclone Wind Signals (TCWS)[28]
Warning Signal Meaning
TCWS #1 winds of 39–61 km/h (21–33 kn; 24–38 mph)
are prevailing or expected to occur within 36 hours
TCWS #2 winds of 62–88 km/h (33–48 kn; 39–55 mph)
are prevailing or expected to occur within 24 hours
TCWS #3 winds of 89–117 km/h (48–63 kn; 55–73 mph)
are prevailing or expected to occur within 18 hours
TCWS #4 winds of 118–184 km/h (64–99 kn; 73–114 mph)
are prevailing or expected to occur within 12 hours
TCWS #5 winds of 185 km/h (100 kn; 115 mph) or greater
are prevailing or expected to occur within 12 hours

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) releases tropical cyclone warnings in the form of Tropical Cyclone Wind Signals (TCWS, or "wind signals").[29] Within this warning system, an area having a wind signal may be under:

  • TCWS #1 - Tropical cyclone winds of 39–61 km/h are prevailing or expected within the next 36 hours.
  • TCWS #2 - Tropical cyclone winds of 62–88 km/h are prevailing or expected within the next 24 hours.
  • TCWS #3 - Tropical cyclone winds of 89–117 km/h are prevailing or expected within the next 18 hours.
  • TCWS #4 - Tropical cyclone winds of 118–184 km/h are prevailing or expected within 12 hours.
  • TCWS #5 - Tropical cyclone winds of 185 km/h or greater are prevailing or expected within 12 hours.

These wind signals are hoisted when an area (in the Philippines only) is about to be directly affected by tropical cyclone winds. Wind signals for specific areas can be escalated to higher signal levels (and the lead times shortened consequently) as a tropical cyclone gains strength and/or gets closer to the areas about to be affected. De-escalation and/or lifting of wind signals are implemented once a tropical cyclone weakens and/or gets farther away from the affected areas. The lead time is also only valid for the first issuance.

Vietnam

[edit]

Vietnam recognises its typhoon season from the beginning of June through to the end of November,[30] with an average of four to six typhoons hitting the country annually.[31] Any tropical cyclones here are monitored by the National Center for Hydro-Meteorological Forecasting (NCHMF), which is the nation's official meteorological agency and was established in January 2003. The NCHMF tracks a storm should it enter the agency's monitoring area range which is within the East Sea to the west of 120°E and north of 5°N. Any storm that enters this area is assigned a number, and is set according to its sequence of its occurrence – as for instance with Bão số 1 etc., which translates to "Storm no. 1". Bão comes from "暴', meaning ferocious, violent or vicious, but in vernacular Vietnamese has come to mean "storm".

In 2014, the Vietnamese government issued Decree no.44/2014, introduced five warning levels,[a] but NCHMF only use three out of five levels to issue typhoon warnings:[32]

  • Orange-decorated "Level 3 disaster risk alert" (High alert)
  • Red-decorated "Level 4 disaster risk alert" (Very high alert)
  • Pink-decorated "Level 5 disaster risk alert" (Disaster alert)

South Pacific basin

[edit]

The Australian Bureau of Meteorology will issue a cyclone watch for a specified part of Australia, when a tropical cyclone is expected to cause gale-force winds in excess of 62 km/h (40 mph) within 24–48 hours and subsequently make landfall.[33] A cyclone warning is subsequently issued for a specified part of Australia when a tropical cyclone, is expected to cause or is causing gale-force winds in excess of 62 km/h (40 mph) within 24 hours and is subsequently expected to make landfall.[33]

The Fiji Meteorological Service (FMS) issues a tropical cyclone alert for the Cook Islands, Fiji, Kiribati, Nauru, Niue, Tokelau and Tuvalu, when a tropical cyclone has a significant probability of causing gale-force winds or stronger winds within 24–48 hours.[34] Gale, storm and hurricane-force wind warnings are subsequently issued for the above areas by FMS, when a tropical cyclone is either causing or expected to cause either gale storm or hurricane-force winds within 24 hours.[34]

Météo-France is responsible for the issuance of tropical cyclone watches and warnings for New Caledonia, Wallis and Futuna, French Polynesia and the Pitcairn Islands.[34] The National Meteorological and Hydrological Services of the Solomon Islands, Samoa, Indonesia, Papua New Guinea, Tonga, New Zealand, Vanuatu, Timor Leste and American Samoa are responsible for their own watches and warnings.[34]

Indian Ocean systems

[edit]

The Indian Meteorological Department (IMD/RSMC New Delhi) is responsible for tracking tropical cyclones within the North Indian Ocean. Météo-France in Réunion (MFR/RSMC La Réunion) is responsible for the issuing advisories and tracking of tropical cyclones in the southwest part of the basin, however, the naming of systems is deferred to the Mauritius and Madagascar weather services.

India

[edit]
Cyclone warning levels
Cyclone watch
Cyclonic storm conditions possible within 72 hours.
Cyclone alert
Cyclonic storm conditions possible within 48 hours.
Cyclone warning
Cyclonic storm conditions expected within 24 hours.
Landfall outlook
Cyclonic storm conditions expected within 12 hours.

The IMD issues warnings in four stages for the Indian coast.

  • Stage 1: Cyclone watch - Issued 72 hours in advance, it discusses the likelihood of development of a cyclonic disturbance in the north Indian Ocean and the coastal region likely to experience adverse weather.
  • Stage 2: Cyclone alert - Issued 48 hours in advance of the commencement of adverse weather over the coastal areas.
  • Stage 3: Cyclone warning - Issued 24 hours in advance of the commencement of adverse weather over the coastal areas. The location of landfall is discussed at this stage.
  • Stage 4: Landfall outlook - Issued 12 hours in advance of the commencement of adverse weather over the coastal areas. The track of the cyclone after the landfall and the possible impact inland is discussed at this stage.

Cyclonic storm conditions mean what winds in excess of 63 km/h (39 mph) are possible.[35]

Mauritius

[edit]

Mauritius Meteorological Services is responsible for naming tropical systems in the South-West Indian Ocean between 55°E and 90°E. They issue four different levels of cyclone warnings for the islands of Mauritius and Rodrigues.

  • Class I cyclone warnings are issued 36 to 48 hours before the islands are affected by wind gusts of at least 120 km/h (75 mph).
  • Class II cyclone warnings are issued when there are 12 hours of daylight left before gusts of 120 km/h (75 mph) affect the islands.
  • Class III cyclone warnings are issued when there are 6 hours of daylight left before gusts of 120 km/h (75 mph) affect the islands.
  • Class IV cyclone warnings are issued when gusts of at least 120 km/h (75 mph) are occurring in the islands.
  • Safety Bulletin Issued for the purpose of: lifting the cyclone warning class III or cyclone warning class IV, as the case may be; and informing the public of the existence of any severe weather conditions associated with the cyclone and other environment risk, depending on the nature and extent of the damage occurred during the passage of the cyclone.
  • Termination Issued when subsequent observations indicate that the risk of cyclonic gusts of 120 kilometres per hour has abated and the cyclone is moving away[36]

Réunion

[edit]

Météo-France issues five levels of alerts for the French overseas department and region of Réunion.[37]

  • Pre-alert/Yellow alert – issued when a tropical system may impact Réunion between 24 and 72 hours.
  • Orange alert – issued when a tropical storm or cyclone may impact Réunion in the next 24 hours.
  • Red alert – issued when a tropical storm or cyclone is impacting part or all of Réunion.
  • Purple alert – issued when a major tropical cyclone with winds exceeding 200 km/h (120 mph) is impacting part or all of Réunion.
  • Safeguard phase – issued when a tropical storm or cyclone is moving away from Réunion, but hazards relating to damage caused by the system, such as fallen trees, flooded roads, mudslides, and downed power lines, still remain.

Military advisories

[edit]

HURCON/TCCOR

[edit]
Main article: HURCON

The United States Department of Defense uses a multi-stage system called the Hurricane Condition (HURCON) in the North Atlantic and the Northeast Pacific and the Tropical Cyclone Condition of Readiness (TCCOR) in the western Pacific to prepare bases and evacuate assets and personnel in advance of adverse weather associated with tropical cyclones.[38]

The alerts are recommended by weather facilities either on base or by central sites like the National Hurricane Center or the Joint Typhoon Warning Center and are generally related to the timing and potential for destructive sustained windspeeds of above 50 kn (58 mph; 93 km/h).[38] Recommendations are then considered by base or area commanders along with other subjective factors for setting the alert status like assets, holidays or the bases experience in emergency preparedness.[38] The bases prefer to set these alerts sequentially, from HURCON or TCCOR 5 with destructive winds expected within 96 hours, through levels 4, 3, 2 and if needed to a series of four different level 1 conditions, however depending on the cyclone's movement or location some of these signals can be skipped.[38][39] After a system passes and stops affecting the base, the authorities can decide to revert to the lowest level or stay in a heightened approach if another tropical cyclone is approaching.[38]

See also

[edit]

Notes

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Tropical cyclone warnings and watches

View on Grokipedia
from Grokipedia
Tropical cyclone warnings and watches are official meteorological alerts issued by national weather services and international centers, such as the National Hurricane Center (NHC) in the United States and Regional Specialized Meteorological Centers (RSMCs) coordinated by the World Meteorological Organization (WMO), to notify coastal and inland populations of the potential or expected impacts from approaching tropical cyclones—rotating storms originating over tropical or subtropical waters with sustained surface winds of at least 34 knots (39 mph). These alerts encompass tropical storms (winds 34–63 knots or 39–73 mph) and hurricanes (winds of 64 knots or 74 mph and greater), focusing on hazards like high winds, heavy rainfall, and storm surge, and are designed to provide lead time for protective actions including evacuations and securing property. Globally, six RSMCs and four Tropical Cyclone Warning Centers (TCWCs) issue such products, tailored to regional conventions but adhering to WMO standards for consistency in monitoring and forecasting cyclones across ocean basins. The primary distinction between watches and warnings lies in the probability and immediacy of impacts: a watch signals that conditions are possible within a specified area, typically issued 48 hours in advance of tropical-storm-force winds to allow initial preparations, while a warning indicates that such conditions are expected, issued 36 hours ahead to prompt urgent actions like completing preparations or evacuating. Specific types include the tropical storm watch (possible winds of 39–73 mph within 48 hours), tropical storm warning (expected within 36 hours), hurricane watch (possible hurricane-force winds of 74 mph or greater within 48 hours), and hurricane warning (expected within 36 hours). Additionally, storm surge watches and warnings address life-threatening coastal flooding, with watches for possible inundation within 48 hours and warnings for expected surges within 36 hours, often specifying water levels above normal . These alerts are disseminated through public advisories, graphics, and emergency broadcasts, with breakpoints—pre-agreed coastal locations—defining the geographic extent to ensure precise communication to affected communities. In the Atlantic and eastern Pacific basins, the NHC issues watches and warnings for U.S. territories and coordinates with international partners, while similar systems operate in the western Pacific (e.g., via the ) and other regions to mitigate the annual global threat of approximately 80–90 tropical cyclones. The effectiveness of these systems relies on advanced forecasting models, data, and collaboration among WMO members to reduce loss of life and property damage from these powerful storms.

General concepts

Definitions and types

A watch is an alert issued when a is expected to affect a specific area within 48 hours, indicating the possibility of tropical-storm-force winds or other hazardous conditions, during which time residents should begin preparing by reviewing evacuation plans and securing property. In contrast, a warning signifies that such conditions are expected within 36 hours, requiring immediate protective actions such as completing preparations, evacuating if advised, and avoiding travel. These timelines allow for a progression from awareness to urgent response, with watches typically issued 48 hours in advance of tropical-storm-force winds and warnings 36 hours ahead. Various types of watches and warnings are defined based on anticipated wind speeds and hazards. A tropical storm watch or warning applies to sustained winds of 34 to 63 knots (39 to 73 mph), covering the range from tropical storm strength onward. A hurricane or warning (the terms vary by basin) is issued for sustained winds of 64 knots (74 mph) or higher, denoting major destructive potential. Additionally, watches and warnings address life-threatening , with a watch for possible inundation within 48 hours and a warning for expected inundation within 36 hours; these were formalized as distinct products in to emphasize surge risks separately from wind threats. Tropical cyclone warnings differ from non-tropical equivalents, such as warnings (34 to 47 knots not associated with tropical systems) or (48 to 63 knots for non-tropical events), primarily in their linkage to the organized structure and track predictability of , which often produce broader and more intense impacts like and surge over large areas. Non-tropical warnings focus on shorter-lived events without the cyclone's rotational dynamics. The terminology has evolved significantly since the 19th century, when visual were first used by the U.S. Army starting in 1881 to indicate approaching storms, including hurricanes, at coastal stations. The inaugural formal hurricane warning was issued on August 21, 1873, by the for a storm threatening the U.S. East Coast. Over time, these gave way to standardized watch and warning systems in the early 20th century, with hurricane-specific flags (two square red flags with black centers for winds over 74 mph) displayed until their discontinuation by the in 1989. Modern systems worldwide have shifted to textual advisories, with some regions adopting color-coded or numbered scales for escalating threats, enhancing communication through radio, television, and digital alerts.

Issuance criteria and timelines

Tropical cyclone warnings and watches are issued based on thresholds of speeds, typically measured over 1-minute or 10-minute averaging periods depending on the basin, as standardized by the (WMO); 1-minute averages are used in the Atlantic and eastern Pacific, while 10-minute averages apply elsewhere. A tropical depression, with sustained winds below 34 knots (63 km/h), generally does not prompt formal watches or warnings unless is forecast, focusing instead on outlooks for potential development. Tropical storm conditions, defined by sustained winds of 34 to 63 knots (63 to 117 km/h), trigger the issuance of watches or warnings when gale-force winds are anticipated to affect coastal or inland areas. For hurricanes, typhoons, or equivalent intense systems with sustained winds of 64 knots (119 km/h) or higher, more severe alerts are activated to address life-threatening winds, emphasizing the Saffir-Simpson Hurricane Wind Scale or analogous intensity metrics in other basins for categorization. Forecast models play a central role in determining issuance timing by predicting cyclone track, intensity, and impacts with sufficient lead time. Global models, such as the (GFS) operated by the U.S. , provide broad-scale guidance on cyclone evolution up to 10 days ahead, while regional models like the Hurricane Weather Research and Forecasting (HWRF) offer higher-resolution simulations of intensity changes within 72-120 hours. These models integrate satellite data, observations, and ensemble techniques to estimate wind radii and propagation speed, enabling forecasters to assess threat probabilities. Standard lead times globally align with WMO guidelines: watches are typically issued 48 to 72 hours before expected tropical storm-force winds, allowing preparation time, while warnings follow 24 to 36 hours prior to gale-force or higher winds impacting the area. Incorporation of secondary hazards refines issuance criteria beyond winds alone. modeling relies on principles accounting for size, forward speed, coastal , and angle of approach to predict inundation levels, often integrated into warnings when surges exceed 1 meter (3 feet) in vulnerable areas. Rainfall forecasts, derived from model outputs like the GFS, evaluate cumulative precipitation risks, issuing alerts for totals that could exceed 150-250 mm (6-10 inches) in 24 hours, leading to flash flooding. As of 2025, the U.S. introduced probabilistic guidance for the , providing probability-based water level heights within 72 hours of potential impacts, while wind speed probabilities extend to 120 hours with established levels. The WMO's Tropical Cyclone Programme (TCP) establishes international standards for coordination, ensuring RSMCs share forecast data and harmonize criteria across basins to support seamless global warning dissemination. This framework promotes the use of multi-model ensembles for improved accuracy and timely alerts, particularly in data-sparse regions.

Atlantic and Northeast Pacific basins

United States

In the , the (NHC), a division of the under the , issues tropical cyclone watches and warnings for the Atlantic basin and the Northeast Pacific east of 140°W . A tropical storm watch is issued when sustained winds of 39 to 73 mph (tropical storm force) are possible within 48 hours, while a tropical storm warning is issued when such winds are expected within 36 hours. Separate hurricane watches and warnings are issued 48 and 36 hours in advance, respectively, of anticipated hurricane-force winds exceeding 73 mph, allowing time for evacuation and preparation along affected coastlines. Storm surge warnings, introduced operationally in 2017, specifically address life-threatening from tropical cyclones, replacing earlier vague advisories to emphasize inundation risks. These warnings are based on probabilistic forecasts of water levels above ground, using models like SLOSH (Sea, Lake, and Overland Surges from Hurricanes) to predict inundation up to 20 feet or more in extreme cases, with watches issued 48 hours ahead and warnings 36 hours before expected impacts. This system highlights areas prone to surge-driven flooding, distinct from wind-based alerts, and has been credited with improving public response during events like Hurricanes Harvey and Irma. To precisely delineate affected areas, the NHC employs a breakpoint system, consisting of over 500 predefined coastal reference points along the U.S. Atlantic and Gulf coasts from Maine to the Texas-Mexico border, as well as segments in Mexico, Central America, the Bahamas, and Cuba. Breakpoints serve as endpoints for watch and warning zones, enabling standardized communication of threats to specific locales like from Chincoteague, Virginia, to Oregon Inlet, North Carolina. In 2025, the NHC introduced enhancements to graphical products, including an experimental forecast graphic incorporating inland watches and warnings with new symbology for overlapping zones, available shortly after advisory issuance. Probabilistic outlooks were expanded in the 7-day Graphical Tropical Weather Outlook, providing formation probabilities for disturbances and extended wind field forecasts up to 72 hours. For the Central Pacific region covering (140°W to 180°), the Central Pacific Hurricane Center (CPHC), co-located with the NHC in , coordinates issuance of similar watches and warnings using consistent criteria. Historically, Hawaii used visual for alerts, with a red flag denoting a hurricane warning, though other signal types were discontinued in the late in favor of modern broadcast methods.

Canada

Environment and Climate Change Canada (ECCC), operating through the Canadian Hurricane Centre (CHC), issues warnings and watches for areas under Canadian jurisdiction, with primary focus on the Atlantic provinces, though coverage extends to the Pacific and coasts as needed. Established in 1987, the CHC provides specialized forecasting and collaborates with the U.S. (NHC) for seamless tracking of systems approaching or affecting . Tropical storm watches and hurricane watches are issued 36 hours before anticipated conditions, while warnings follow 24 hours prior to arrival. These products apply to coastal and inland areas, with a tropical storm watch or warning declared for expected sustained of 63–117 km/h, and a hurricane watch or warning for winds of at least 118 km/h. The shorter lead times compared to NHC standards reflect adjustments for Canada's northerly latitude, where systems often undergo rapid post-tropical transition, limiting forecast reliability beyond 36 hours. On the , ECCC addresses remnants of western Pacific typhoons that occasionally cross the ocean and impact with heavy rainfall, strong winds, and ing, issuing integrated wind, rain, and special weather statements rather than dedicated alerts once the system loses tropical characteristics. systems, including rare post-tropical influences or hybrid events, prompt coordinated marine and weather warnings for northern territories, with risks addressed through separate heavy rainfall or coastal advisories. threats are incorporated into broader coastal warnings rather than standalone tropical products, supported by ECCC's national coastal prediction program launched in 2024. All ECCC tropical cyclone information statements, watches, and warnings are disseminated bilingually in English and French via official channels, ensuring equitable access for Canada's diverse population. This standardized terminology, aligned with NHC practices since the CHC's inception, was further refined in the late 1990s through annual reports to improve consistency in public messaging.

Northwest Pacific basin

Japan

The Japan Meteorological Agency (JMA) operates a tiered advisory system for typhoons in the Northwest Pacific basin, focusing on wind impacts, rainfall, and associated hazards to support timely public response. Special weather warnings are issued for expected sustained winds of 20 m/s or greater, alerting areas to potential gales that could disrupt daily activities and infrastructure. Typhoon warnings are escalated for winds of 30 m/s or more, emphasizing severe structural damage risks from strong gusts and flying debris. For extreme cases, such as typhoons with central pressures of 930 hPa or lower or maximum sustained winds of 50 m/s or higher, JMA issues "emergency warnings" to indicate life-threatening conditions far exceeding standard thresholds, as seen in historical events like Typhoon Vera in 1959. JMA classifies intensity using 10-minute sustained wind speeds, with "strong typhoons" at 33–44 m/s, "very strong typhoons" at 44–54 m/s, and "violent typhoons" at 54 m/s or above, guiding the urgency of advisories. Warnings are typically issued 24–48 hours before anticipated , supported by extended track forecasts up to 120 hours that have evolved since the to incorporate numerical models and data for improved accuracy. This allows for preparatory measures, including the activation of the Storm Surge Watch Scheme since 2011, which integrates forecasts with predictions to forecast water level rises exceeding normal . Evacuation advisories are coordinated closely with local governments under the Disaster Countermeasures Basic Act of 1961, where mayors issue orders based on JMA's alert levels—ranging from advisory (Level 2) for preparation to emergency (Level 5) for immediate safety actions. The modern warning framework traces its origins to 1951, when systematic records and prefecture-level alerts were established, evolving through milestones like the introduction of 24-hour track forecasts in 1952 and municipality-level precision by 2010 to enhance localized responses. JMA also links advisories with warnings for events, issuing dedicated warnings when predicted inundation reaches danger levels, as refined quantitatively since to protect coastal populations.

China

The (CMA) operates a standardized four-tier, color-coded warning system for tropical cyclones in the Northwest Pacific basin, aimed at providing timely alerts for gale-force winds and associated hazards such as storm surges and heavy rainfall. This system classifies warnings based on forecasted wind intensities near coastal and inland areas, facilitating coordinated emergency responses across provinces. Warnings are typically issued 24 to 72 hours in advance, depending on the cyclone's projected path and intensification, drawing on numerical models and observational data to predict impacts. The color tiers escalate with severity: a warning indicates expected average winds of Beaufort force 6 or gusts of force 8 within 24 hours, signaling potential disruptions to maritime activities and requiring precautionary measures; yellow indicates average force 8 or gusts force 10 within 24 hours, prompting closures and restrictions; orange denotes average force 10 or gusts force 12 within 12 hours, triggering evacuations in vulnerable areas; and red applies to average force 12 or gusts within 6 hours, mandating full-scale emergency activations including shutdowns of ports and airports. These thresholds align with national meteorological standards to ensure public safety, with updates disseminated via media, apps, and sirens. In Province, a key coastal region frequently affected by typhoons, the CMA's national system is supplemented by provincial-level warnings that incorporate historical visual signaling traditions. Coastal cities like and maintain ball signal systems at ports, where numbered cones or balls hoisted on masts historically indicated wind force levels—such as signal No. 1 for winds up to Beaufort 7 and No. 3 for force 8 or above—serving as quick maritime alerts since the early . These local adaptations enhance the color-coded framework, particularly for communities and shipping. Post-2000 reforms under the CMA have promoted greater integration of warning mechanisms, including coordination with Hong Kong's Observatory for cross-border alerts in the . In 2025, enhancements to satellite integration, notably from the newly operational Fengyun-3H satellite, have enabled earlier detection of cyclone formation, improving forecast lead times by up to 12 hours for high-impact events. The CMA also collaborates with the as the Regional Specialized Meteorological Center for the Northwest Pacific to refine basin-wide advisories.

Philippines

In the Philippines, the Philippine Atmospheric, Geophysical and Astronomical Services Administration () issues (TCWS) to warn the public of impending strong winds associated with tropical cyclones entering the (PAR). The system consists of five levels, each corresponding to expected sustained wind speeds and lead times before the onset of those winds: Signal No. 1 for 39-61 km/h within 36 hours, Signal No. 2 for 62-88 km/h within 24 hours, Signal No. 3 for 89-117 km/h within 18 hours, Signal No. 4 for 118-184 km/h within 12 hours, and Signal No. 5 for 185 km/h or greater within 12 hours. These signals are raised or lowered based on the cyclone's forecasted intensity, the extent of its wind field, and its projected movement relative to affected areas, with advisories issued at the provincial or city level and potentially skipping levels during . The wind speed thresholds align with international standards such as the for gale-force and higher winds. The TCWS system originated from early 20th-century numbered storm signal codes developed under U.S. Weather Bureau influence during American colonial administration, with formalization by PAGASA's predecessor in the 1930s and expansions in the mid-20th century, including the addition of higher levels in the 1960s and 1970s to reflect increasing cyclone threats. Public dissemination of these signals historically involved raising physical flags at weather stations and community posts, supplemented by sirens in coastal and rural localities, though modern communication primarily relies on media broadcasts, social media updates, and official bulletins to ensure widespread reach. PAGASA integrates gale warnings directly into the TCWS framework, as lower signals (No. 1 and No. 2) address strong to gale-force winds, while separate color-coded storm surge advisories (yellow, orange, red) are issued concurrently for coastal areas at risk of inundation, often overlapping with higher TCWS levels. PAGASA coordinates closely with the National Disaster Risk Reduction and Management Council (NDRRMC) and units' disaster risk reduction and management offices (DRRMOs) to translate TCWS into actionable responses, such as preemptive evacuations, resource prepositioning, and community drills in signal-affected areas. In the , enhancements to the system include the launch of the PANaHON mobile app in late 2025, which provides real-time, geolocated TCWS updates and alerts via push notifications, particularly benefiting rural and remote areas with limited through SMS integration and consolidated regional maps. This upgrade builds on the 2022 revision of TCWS thresholds to improve forecast accuracy and public comprehension.

Vietnam

In Vietnam, the National Center for Hydro-Meteorological Forecasting (NCHMF), under the Ministry of Natural Resources and Environment, is responsible for issuing warnings and watches, primarily for typhoons affecting the country's extensive 3,260 km coastline in the Northwest Pacific basin. The system emphasizes wind-based alerts to prompt evacuations and preparations, integrating with separate warnings for associated floods and storm surges issued by hydrological centers. Lead times are tailored to Vietnam's elongated geography, providing extended notice for northern and southern regions to account for varying storm progression speeds along the coast. The core framework is a four-level warning system established by Decision No. 46/2014/QD-TTg on , warning, and communication, which categorizes alerts based on sustained wind speeds near the storm's center and projected lead times before impact. Level 1 warnings apply to tropical depressions with winds of 39–61 km/h ( levels 6–7), issued at least 48 hours in advance when the system is expected to enter the East Sea or approach within 300–500 km of the coast. Level 2 targets storms with winds of 62–88 km/h (levels 8–9), focusing on systems 500–1,000 km offshore with potential within 48 hours. Level 3 addresses severe storms with winds of 89–116 km/h (levels 10–11), triggering urgent actions when the center is within 300 km or advancing rapidly. Level 4, the highest, covers typhoons exceeding 117 km/h (levels 12 and above), with immediate evacuation mandates for coastal areas when is imminent, often within 24 hours or less. Depression alerts are included under Level 1 to provide early monitoring, even if intensification is uncertain. This structure stems from post-2010 reforms under the Law on Natural Disaster Prevention and Control (No. 33/2013/QH13), which overhauled the system to enhance forecasting accuracy and align with international standards from the , including standardized wind thresholds and multi-channel dissemination. Unlike visual flag systems in neighboring countries, Vietnam relies on media broadcasts via national television (VTV), radio (), SMS alerts, and online platforms without public hoisting of signals. In the 2020s, efforts addressed dissemination gaps in rural and remote areas through expanded community-based early warning networks, digital apps for real-time updates, and partnerships with local authorities to improve reach in flood-prone deltas and highlands. These enhancements have extended effective warning coverage, enabling proactive measures like evacuations during events such as Yagi in 2024.

North Indian Ocean basin

India

The (IMD), designated as the (RSMC) for Tropical Cyclones over the North Indian Ocean, issues warnings for cyclones affecting the and coasts. These warnings follow a structured four-stage process to provide timely alerts to government officials, enabling preparation and response in vulnerable coastal regions. The first stage, Pre-Cyclone Watch, is issued 72 hours in advance when a cyclonic disturbance is likely to develop into a depression over the , specifying potential intensification and impacted coastal areas. This alert is disseminated by the of to the , senior officials, and Chief Secretaries of concerned maritime states. The second stage, Cyclone Alert, follows 48 hours prior to the expected onset of adverse weather, detailing the cyclone's location, estimated intensity, direction and speed of movement, likely intensification, and affected coastal districts, along with preparatory advice for fishermen, the public, media, and managers. Issued by Area Cyclone Warning Centres (ACWCs), Cyclone Warning Centres (CWCs), and the Cyclone Warning Division (CWD) at headquarters, it uses a since the post-monsoon season of 2006. The third stage, Cyclone Warning, is provided at least 24 hours before impacts coastal areas, including precise forecasts of the point, cyclone position and intensity, time of , heavy rainfall, gale winds, heights, and associated impacts, with specific action recommendations. Bulletins are updated every three hours by ACWCs, CWCs, and CWD, employing an orange color code. The fourth stage, Post-Landfall Outlook, covers up to 12 hours after , outlining the cyclone's post-landfall direction of movement and continued adverse weather over inland areas, marked by a red color code. IMD classifies cyclone intensity based on maximum sustained surface wind speeds, averaged over three minutes, as follows:
CategoryWind Speed (knots)Wind Speed (km/h)
Depression17–2731–50
Deep Depression28–3351–61
34–4762–88
Severe Cyclonic Storm48–6389–117
Very Severe Cyclonic Storm64–89118–166
Extremely Severe Cyclonic Storm90–119167–221
Super Cyclonic Storm≥120≥222
These classifications guide the detail and urgency of warnings. Warnings incorporate forecasts of storm surges, which can inundate coastal areas by several meters, and heavy rainfall leading to flooding, with specific estimates provided in the Cyclone Warning stage to aid evacuation and protection. IMD coordinates closely with state governments through teleconferences and direct bulletins to Chief Secretaries, ensuring localized dissemination via , , and other channels. In 2025, IMD enhanced its forecasting capabilities with AI/ML-based data-driven models integrated alongside systems, improving cyclone track and intensity predictions through specialized GPU infrastructure and collaborations with institutions like ECMWF. This includes the Advanced for intensity estimation and augmented high-power with 22 PetaFLOPS capacity, enabling more accurate and timely alerts for the North basin.

Bangladesh and other countries

In Bangladesh, the Bangladesh Meteorological Department (BMD) coordinates with the India Meteorological Department (IMD) through the WMO/ESCAP Panel on Tropical Cyclones to receive forecast bulletins, upon which it issues localized "danger signals" numbered from 1 to 10 to indicate escalating wind intensities and associated risks. These signals categorize threats progressively, escalating from gales (around 50 km/h) to extreme cyclone conditions (over 120 km/h for the highest signals), often accompanied by severe storm surges in the country's vulnerable Ganges-Brahmaputra delta regions. BMD typically provides 24- to 48-hour advance warnings to enable evacuations and preparations, emphasizing surge-prone coastal areas where historical events like Cyclone Sidr in 2007 have demonstrated the need for rapid response. In , the (PMD) maintains a Warning Centre in to monitor and issue advisories for systems forming in the , drawing on IMD's regional forecasts for tracking and intensity predictions as part of cross-border collaboration. These alerts focus on potential impacts to coastal areas like and , using severity levels to guide local authorities in issuing evacuation notices and maritime restrictions, particularly for infrequent but intensifying storms in this basin. Sri Lanka's Department of Meteorology (DMS) similarly coordinates with IMD for tropical cyclones originating in the , receiving shared data to issue tailored wind warnings that specify gust speeds and durations to inform public safety measures. The DMS emphasizes evacuation orders for eastern and northern coastal districts, where cyclones like Roanu in 2016 have prompted enhanced protocols for sheltering vulnerable populations and securing infrastructure. Similarly, the and coordinate with IMD for warnings tailored to their coastal vulnerabilities. Across , , , , and , tropical cyclones often produce cross-border effects due to the interconnected North basins, leading to frequent reliance on joint forecasting efforts; in the , the WMO/ESCAP Panel has facilitated improvements such as standardized data exchange and impact-based predictions to bolster regional resilience.

Southern Hemisphere basins

Southwest Indian Ocean

In the Southwest Indian Ocean basin, spanning latitudes from the southward to 40°S and longitudes from 20°E to 80°E, the (RSMC) in La Réunion, operated by , serves as the primary authority for monitoring, forecasting, and issuing advisories to (WMO) member states. Established under WMO guidelines, the RSMC provides global bulletins every 6 hours once a system is designated for tracking, including position, intensity estimates, and forecasts extending up to 120 hours, with a focus on potential impacts such as heavy rainfall, strong winds, and storm surges. These advisories support national meteorological services in issuing localized warnings, emphasizing coordination to ensure timely dissemination across vulnerable island nations and coastal regions. Météo-France employs a standardized intensity scale for classifying systems in the basin, ranging from Tropical Depression (sustained winds of 28–33 knots) to Moderate Tropical Storm (34–47 knots), Severe Tropical Storm (48–63 knots), (64–89 knots), Intense Tropical Cyclone (90–115 knots), and Very Intense Tropical Cyclone (over 115 knots). Warnings are triggered when systems reach or are forecast to reach tropical storm strength (winds ≥34 knots, approximately 35 knots threshold for advisory issuance), with bulletins incorporating risk assessments to alert on potential and inundation. For La Réunion specifically, Météo-France issues color-coded vigilance alerts—yellow for pre-alert (distant threat), orange for approaching danger, and red for imminent impact—based on expected gusts exceeding 120 km/h and other hazards. Coordination with neighboring services, such as Meteorological Services and Madagascar's sub-regional centre (west of 55°E), ensures harmonized warnings across the basin; for instance, adopts a similar Class I–IV system aligned with RSMC data, where Class I signals a distant threat (36–48 hours before gusts ≥120 km/h), Class II indicates approach (about 12 hours prior), Class III denotes threat (6 hours prior), and Class IV confirms or ongoing severe conditions. This collaborative framework, formalized through hourly data exchanges during active events, has been operational since the 1980s, with the basin's Operational Plan first adopted in following its formulation in at the RA I Committee session in . bulletins are integrated into RSMC safety advisories to highlight risks like tidal surges up to several meters in low-lying areas. Recent enhancements, effective for the 2024–2025 season, include the adoption of a formal subtropical storm definition by the RA I Tropical Cyclone Committee to improve early identification of hybrid systems, alongside a planned upgrade to Météo-France's public website in November 2024 for better real-time access to advisories and visualizations. These build on ongoing improvements in satellite data utilization, such as microwave imagers (e.g., AMSU) and scatterometers, enabling earlier watches for systems potentially reaching 35 knots within 72 hours, thus extending lead times for distant threats like Class I equivalents.

Australian region

In the Australian region, the (BoM) classifies tropical cyclones using a five-category scale based on maximum mean s near the center, with Category 1 representing the least intense systems (63–88 km/h) and escalating to Category 5 for the most severe (>200 km/h). Gust speeds are typically 1.4 times the mean , reaching up to 125 km/h for Category 1 and exceeding 279 km/h for Category 5. This scale, aligned with other intensity measures, emphasizes potential structural damage from , with higher categories indicating increasing risks to and . BoM issues a Tropical Cyclone Watch when gale-force winds (≥63 km/h) are expected to affect coastal or island communities within 24 to 48 hours, providing time for preparation; this is followed by a Tropical Cyclone Warning when gales are imminent within 24 hours or already occurring, with updates every three hours during active threats. These advisories cover the Australian region spanning 90°E to 160°E and south of about 10°N to 40°S, including remote islands like Christmas, Cocos (Keeling), Lord Howe, and Norfolk. The three regional Tropical Cyclone Warning Centres (TCWCs)—located in Perth (Western Australia), Darwin (Northern Territory), and Brisbane (Queensland)—coordinate monitoring, forecasting, and issuance of bulletins to ensure comprehensive coverage across the vast area. In July 2024, implemented the Australian Warning System (AWS), an impact-based framework integrated with BoM's meteorological products to deliver consistent, hazard-specific alerts for tropical cyclones, including associated and flooding risks. AWS uses three escalating levels—Advice (no immediate threat, focus on preparation), Watch and Act (possible threat to life and property, ready to respond), and Emergency Warning (imminent danger, act immediately)—with tailored calls to action such as evacuating low-lying areas prone to surge or avoiding floodwaters. This system enhances public understanding by prioritizing localized impacts over alone, complementing the traditional category classifications. For the 2025–26 season, BoM provides extended outlooks, including multi-week probabilistic forecasts and seven-day track predictions, to support coordination with Pacific partners such as those in for cross-basin threats. These outlooks, updated regularly, inform international efforts under the to mitigate regional risks from potential cyclone activity.

South Pacific Ocean

The (RSMC) , operated by the Fiji Meteorological Service, is responsible for monitoring and issuing warnings for tropical s in the South Pacific basin east of 160°E , extending to the date line. It issues cyclone watches approximately 48 hours in advance of expected gale-force winds (≥34 knots or 63 km/h, based on 10-minute sustained averages) and upgrades to warnings 24 hours prior to the onset of such conditions, providing critical lead times for preparation in vulnerable nations. These warnings include detailed track forecasts up to 72 hours ahead, along with 5-day outlooks for potential development, helping to mitigate risks across the . RSMC Nadi classifies tropical cyclones using a 1-5 category scale based on maximum 10-minute sustained wind speeds, where Category 1 represents destructive winds of 48-63 knots, escalating to Category 5 for catastrophic winds exceeding 118 knots; this system parallels the Australian scale but is tailored for Pacific island contexts. For instance, during the 2023-2024 season, RSMC forecasted four to five tropical cyclones in its , with one likely reaching severe Category 3-5 status, emphasizing the need for robust alerting in archipelagic environments. The , managed by New Zealand's , complements RSMC by providing specialized advisories for cyclones approaching or impacting , particularly the [North Island](/page/North Island), where ex-tropical remnants often bring heavy rain and strong winds. issues warnings integrated into broader alerts, which may overlap with advisories from the National Emergency Management Agency (NEMA) in cases of risks, ensuring coordinated public messaging during multi-hazard events. Lead times for these warnings align closely with those from Australia's , typically offering 24-48 hours of notice for gale-force impacts to support evacuations and infrastructure protections. Coordination between RSMC Nadi and TCWC Wellington is facilitated through the World Meteorological Organization's RA V Tropical Cyclone Committee, which ensures seamless information sharing for small island states like Vanuatu and Tonga, where cyclones frequently track through shared maritime zones. For example, during Tropical Cyclone Harold in 2020, joint advisories enabled timely evacuations in Vanuatu and Tonga, highlighting inter-agency collaboration via radio broadcasts, SMS alerts, and community networks to reach isolated communities. Historical gaps in warning coverage for remote Pacific islands, evident in events like Cyclone Pat in 2010 that strained communication in , have been addressed since the 2010s through enhanced modeling and regional initiatives. Post-2015 , which devastated , investments in models and satellite data integration improved forecast accuracy by up to 20% for 48-hour tracks, filling voids in real-time monitoring for dispersed atolls. The CREWS Pacific 2.0 project (2021-2025), funded by the and partners, further bolstered these efforts by training forecasters in impact-based forecasting and establishing community alert protocols in , , and . The project concluded in June 2025, with a successor phase, Pacific 3.0, approved in April 2025 to build on these advancements. Remote areas in the South Pacific face unique challenges in cyclone warning dissemination, including geographic isolation, limited infrastructure, and vulnerability to power outages, which can delay alerts to outer islands in nations like and . These issues exacerbate risks for subsistence communities reliant on and agriculture, where even 24-hour warnings may not suffice for relocation without reliable transport. International aid is often triggered by predefined thresholds in frameworks like Fiji's Anticipatory Action Protocol, activated when RSMC forecasts a Category 3+ within 48 hours of , enabling pre-positioning of relief supplies such as shelter kits and tools for up to 2,000 affected households through partners like the Red Cross and FAO. Similar mechanisms in and link warning severity to UN and bilateral aid releases, prioritizing rapid response to minimize post-storm displacement.

Special warning systems

Military advisories

Military advisories for tropical cyclones, known as Hurricane Conditions of Readiness () and Tropical Cyclone Conditions of Readiness (TCCOR), are specialized alert systems employed by the to prepare military bases and personnel for impending destructive winds associated with these storms. These systems enable commanders to implement phased readiness measures, such as securing equipment, evacuating non-essential assets, and ensuring personnel safety, distinct from civilian warning structures by emphasizing operational continuity and . The system, primarily used by the U.S. Navy and , consists of five conditions based on the anticipated arrival of sustained surface winds exceeding 58 mph (50 knots), which align with the threshold for destructive impacts. 5 is declared when such winds could arrive within 96 hours, prompting initial planning and resource stockpiling; 4 follows at 72 hours, with actions like securing outdoor assets; 3 at 48 hours intensifies preparations, including potential mission halts; 2 at 24 hours mandates sheltering and evacuation of vulnerable personnel; and 1 at 12 hours signals imminent with maximum winds, requiring all non-essential personnel to be in secure locations. An emergency sub-level, 1E, is activated when destructive winds of 50 knots (58 mph) sustained or gusts of 60 knots (69 mph) or greater are occurring, confining personnel to shelters until cleared. TCCOR, the counterpart system adopted by the U.S. Marine Corps and extended to some installations in tropical-prone regions, mirrors HURCON's structure but starts at 72 hours and incorporates explicit provisions for evacuating non-essential personnel to minimize exposure. TCCOR 4 indicates possible destructive winds (50 knots sustained or 60-knot gusts) within 72 hours, initiating supply gathering and family readiness briefings; TCCOR 3 at 48 hours escalates to and potential dependents' evacuation; TCCOR 2 at 24 hours requires securing facilities and halting non-critical operations; TCCOR 1 at 12 hours indicates destructive winds expected, with sublevels: 1C (Caution) when current winds are 34–49 knots (39–56 mph), requiring full lockdowns and securing all assets; 1E () when destructive winds are occurring, confining personnel to shelters; and 1R (Recovery) after winds subside, for assessment. These levels are set year-round in active seasons, such as to in the Pacific, to align with patterns. These advisories apply globally to U.S. military bases in the Pacific and Atlantic basins, including installations like in , , and in , ensuring standardized responses across theaters. Declarations are coordinated with the (JTWC) for Pacific and Indian Ocean threats, which provides forecast data to trigger /TCCOR levels, while Atlantic bases rely on inputs for similar synchronization. Originating from post-World War II advancements in military , when forecasting improved through enhanced reconnaissance, and TCCOR evolved to formalize base-wide protocols amid increasing U.S. presence in cyclone-vulnerable regions. In the 2020s, these systems incorporated digital enhancements, such as real-time tracking via JTWC's online warning graphics and virtual collaboration tools, improving decision-making during events like the record .

Aviation and maritime alerts

Aviation alerts for tropical cyclones primarily consist of Significant Meteorological Information (SIGMET) messages, which warn pilots of hazardous conditions such as severe , icing, or thunderstorms associated with the storm, typically valid for up to 6 hours and issued at least every 6 hours while winds remain at or above 35 knots (64 km/h). These advisories, prepared by designated Meteorological Watch Offices (MWOs), cover the vertical and horizontal extent of -related dangers within 4-6 hours of the forecast position, enabling adjustments to avoid risks. Complementing SIGMETs, Notices to Air Missions (NOTAMs) notify aviators of airport closures or restrictions, often issued up to 72 hours in advance when impacts like high winds or flooding threaten operations, as seen in suspensions during storms like Super Uwan in 2025. Maritime alerts focus on ensuring safe navigation through broadcasts of tropical cyclone warnings via the NAVAREA system, coordinated by the (WMO) and International Maritime Organization (IMO), which disseminates navigational hazards including storm tracks and intensity to vessels in designated sea areas. and storm warnings, indicating sustained winds of 34-63 knots (39-72 km/h) or higher, are issued 24-48 hours in advance for affected marine zones, often through SafetyNET or services to alert ships of impending tropical cyclone threats. These warnings prioritize offshore safety, with graphical products providing wind forecasts up to 48 hours for strategic routing. The (JTWC) plays a key role in issuing unofficial advisories for and maritime interests, particularly in the North-West Pacific, South Pacific, and basins, supplementing official warnings with detailed forecasts used by military and commercial operators. These efforts align with (ICAO) and WMO standards, which mandate global exchange of information through systems like the Significant Weather Information Service (SWIS) and require MWOs to provide timely SIGMETs and advisories for international air and sea traffic. In coordination with military advisories, JTWC outputs support broader operational resilience for transport sectors. In 2025, integration of data from uncrewed surface vehicles (USVs) and drones has enhanced offshore alerts, with NOAA deploying systems like the Oshen C-Star USVs to collect real-time ocean and atmospheric observations, improving the accuracy of maritime warnings in remote areas.

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