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HOME > Climate & Weather Linkage > Global Tropics Benefits/Hazards

Last Updated - 05.26.20 (Routine)


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Tropical Cyclone Formation KMZ / KML / SHP KMZ / KML / SHP
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Lower Tercile Precipitation KMZ / KML / SHP KMZ / KML / SHP
Above Average Temperatures KMZ / KML / SHP KMZ / KML / SHP
Below Average Temperatures KMZ / KML / SHP KMZ / KML / SHP

Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 05.26.20 Valid: 05.27.20 - 06.09.20
While an active intraseasonal signal is still present in the CPC velocity potential based MJO index as well as the RMM-based MJO index, the overall pattern has become increasingly incoherent over the past several days. The amplitude of the enhanced convective envelope in particular has decreased as a Kelvin wave propagated across the Pacific, well ahead of the rest of the signal. Despite the regime of enhanced trade winds across much of the Pacific basin, the Kelvin wave appears to be convectively coupled with the North Pacific ITCZ, and a zonally narrow band of anomalous westerlies is present south of Mexico. Dynamical model MJO index forecasts track this Kelvin wave better than any other coherent feature, with most model forecasts showing the signal returning to the Indian Ocean towards the end of Week-2 or weakening. Based on these recent observations and forecasts, a canonical MJO evolution from the Maritime Continent to the Pacific is not anticipated, but the Kelvin wave is likely to influence the tropical convective pattern, particularly across the Western Hemisphere.

Cyclone Amphan made landfall over West Bengal on 20 May at Category-2 intensity on the Saffir-Simpson scale, causing considerable damage across northeastern India and Bangladesh. This single tropical cyclone generated more than double the climatological accumulated cyclone energy (ACE) observed over the North Indian Ocean basin during the entire Spring season. On 21 May, Tropical Storm Mangga formed over the South Indian Ocean. Following extratropical transition and merging with a cold front, the remnants of TS Mangga generated widespread wind damage across Western Australia.

During Week-1, as the Kelvin wave crosses the East Pacific and with upper-level high pressure already in place, conditions will become increasingly favorable for tropical cyclone formation over the East Pacific basin. The NHC is monitoring an area just south of Mexico and Guatemala, and forecasts a 70-percent chance of a tropical depression forming in this region over the next 5 days. More GEFS ensemble members depict tropical cyclone activity at days 5-8 than days 1-4; therefore, there is high confidence for tropical cyclogenesis in this region during the Week-1 period. As the Kelvin wave progresses eastward, the favorable area is anticipated to expand to include the Gulf of Mexico and western Caribbean. Numerous GEFS ensemble members depict the formation of a tropical cyclone in this region, with a clustering of tracks bringing the potential cyclone towards the Florida peninsula, the northern Gulf Coast, or as far east as central Cuba and the Bahamas. There is a high degree of uncertainty regarding this forecast, and interests in the southeastern US, Mexico, and the western Caribbean should monitor the latest forecasts. A moderate potential for tropical cyclone formation is forecast for the Week-2 period extending from the East Pacific south of Mexico to the Bay of Campeche, southeastern Gulf of Mexico, and the far northwestern Caribbean. Elsewhere, dynamical models show a moderate potential for a disturbance west of India to become a tropical cyclone as it moves slowly northward across the Arabian Sea. Several GEFS ensemble members depict a second tropical cyclone formation near Oman; however, confidence is too low at this time to include a second Arabian Sea formation hazard on the outlook.

Given the increasingly incoherent presentation of the intraseasonal signal, the forecasts for above- and below- normal precipitation are based on a consensus of bias-corrected CFS and ECMWF guidance, and potential tropical cyclone activity discussed above. Suppressed rainfall is favored across southeast Asia, the northwestern Pacific basin, and the equatorial central Atlantic during Week-1, while the central Maritime Continent and the East Pacific and western Atlantic basins are favored to be active. A disturbance near the US Southeast coastline may bring heavy rainfall to the Carolinas early in the period. A heat wave is ongoing across much of India, and is favored to continue early in the Week-1 period. Excessive heat is also likely across the US Southwest.

During Week-2, suppressed rainfall is favored to continue over the northwestern Pacific region, while a moderate potential for enhanced rainfall shifts eastward across the Maritime Continent and the South Pacific, including American Samoa. An area of enhanced rainfall is possible over the western Indian Ocean north of Madagascar as the Kelvin wave returns to the Indian Ocean. While excessive heat is favored to diminish over India, a period of hot weather is possible across parts of Southeast Asia.

Forecasts over Africa are made in consultation with CPC’s international desk, and can represent local-scale conditions in addition to global-scale variability.

Product Release Information

The full Global Tropics Hazards and Benefits Outlook (GTH) is released once per week every Tuesday at 1730 UTC (1830 UTC when on standard time) including U.S. federal holidays. At the time of product release, there is a live briefing (available via webinar) open to all interested parties in which the latest conditions in the Tropics and the just released outlook and associated impacts are discussed. There is an opportunity to ask questions after the briefing and the briefings are available at the Live Briefing Archive and soon will be recorded.

CPC also issues an operational update of this product every Friday by 1730 UTC to further support the NWS regions. The update only spans the release period from June 1 through November 30 and a region from 120E to the Prime Meridian in longitude and from the equator to 40N in latitude. The update does not extend the time horizon of the product, but rather applies for the remaining 4 days of the previous Week-1 time period and Days 5-11 from the previous Week-2 period. This page will depict both the original and updated outlook maps as well short text outlining the forecast rationale for any changes.

Product Description

The Global Tropics Hazards and Benefits Outlook is a forecast for areas with elevated odds for above- or below-median rainfall, above- or below-normal temperatures and regions where tropical cyclogenesis is favored for the upcoming Week-1 and Week-2 time periods. The rainfall outlook is for precipitation integrated over a week and targets broad-scale patterns, not local conditions as they will be highly variable. Above(below) median rainfall forecast areas are depicted in green and yellow respectively. Above(below) normal temperature forecast areas are depicted in orange and below respectively. Favored areas for tropical development are shown in red. Two measures of confidence are indicated, high (solid) and moderate (hatched) and are currently subjective in nature and not based on an objective system. Work towards a probabilistic format of the product and so an objective measure of confidence is ongoing. The weekly verification period ranges from 00 UTC Wednesday to 00 UTC the following Wednesday.

Along with the product graphic, a written text outlook discussion is also included at release time. The narrative provides a review of the past week across the global Tropics, a description of the current climate-weather situation, the factors and reasoning behind the depicted outlook and notes on any other issues the user should be aware of. The discussion discusses the impacts in the Tropics as well as potential impacts in the Extratropics when relevant.

Product Physical Basis

The product synthesizes information and expert analysis related to climate variability across multiple time scales and from various sources, including operational climate monitoring products. The physical basis for the outlooks include El Nino-Southern Oscillation (ENSO) , the Madden-Julian Oscillation (MJO), strength and variations of the monsoon systems, other coherent subseasonal tropical variability such as atmospheric Kelvin waves (KW), Equatorial Rossby waves (ERW), African easterly waves, as well as interactions with the extratropical circulation (i.e. high latitude blocking, low-latitude frontal activity, etc.).

Product Forecast Tools

The outlook maps are currently created subjectively based on a number of forecast tools, many of which are objective. The final depiction is an assessment of these forecast tools based on a number of factors to create the final product. Work is ongoing to create an objective consolidation of some of the available forecast tools to serve as a first guess for the forecaster. Forecast tools include MJO composites, empirical and dynamical based MJO, ERW and KW forecasts, and raw dynamical model guidance from a number of modeling systems. Tropical cyclone areas are based on MJO composites and statistical and dynamical tropical cyclone forecasts as well as raw model forecast guidance.

Product Purpose

The product supports the NOAA mission in three primary ways:

  1. Assess and forecast important changes in the distribution of tropical convection (i.e., potential circulation changes across the Pacific and North America sectors) and communicate this information to NWS forecasters
  2. Provide advance notice of potential hazards related to climate, weather and hydrological events across the global tropics (including tropical cyclone risks for several NWS regions)
  3. Support various sectors of the U.S. economy (finance, energy, agriculture, water resource management) that have foreign interests.

Product Partners

The product is created through collaboration with other NOAA centers, [the National Hurricane Center (NHC) and the Central Pacific Hurricane Center (CPHC)], the Department of Defense [The Joint Typhoon Warning Center (JTWC) and the Naval Postgraduate School (NPS)], the Australian Bureau of Meteorology, Taiwan Central Weather Bureau, the State University of New York at Albany (SUNY) and the Center for Climate and Satellites (CICS), among other collaborators.

Product Users and Applications

Known users include U.S. government agencies such as NOAA [National Weather Service (NWS), River Forecast Centers (RFCs), the National Marine Fisheries Service (NMFS), the Department of the Interior (U.S. Forest Service), aid organizations (U.S. and international Red Cross, USAID), domestic and global private sector interests (financial, energy, water resource management and agricultural sectors), international weather services and various media meteorologists.

Some special applications of the product in the past include extended range predictions to support Haiti earthquake and Deepwater Horizon oil spill relief efforts as well as support for the Dynamics of the MJO (DYNAMO) scientific field campaign held from October 2011 through March 2012.

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