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

Last Updated - 11.17.17 (Update)


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Global Tropical Hazards/Benefits Assessment

Global Tropics Hazards and Benefits Outlook Discussion

Updated discussion
Last Updated: 11.17.17 Valid: 11.18.17 - 11.28.17
The MJO remained weak, with the major influences on the patterns in tropical convection coming from the low frequency state and a Kelvin wave moving across the western Pacific. Through the next 11 days, the atmosphere is not expected to be consistent with robust MJO activity, and the major center of tropical convection is likely to be over the Maritime Continent.

Tropical depression thirty formed just west of the Philippines on 17 Nov, and is predicted to track toward Vietnam. The National Hurricane Center indicates a 20% chance of tropical cyclone formation over the western Caribbean during the next 5 days, as a persistent area of low pressure is indicated in many of the models. Some models indicate the potential for tropical cyclone formation through the remainder of the forecast period, though confidence is low. Formations along the tail ends of cold front are common during this time of year.

Frontal activity and the area of low-pressure over the western Caribbean are likely to contribute to above average rains for Florida during the 5-11 day period. Elsewhere, areas of predicted above/below average rainfall align with model output and low-frequency variability.

------------ Prior discussion, from 14 Nov, follows ---------------------

The MJO remained weak during the past 7 days, with the remaining signal over the Maritime Continent. A La Nina advisory was issued, as the atmosphere and ocean measurements are now reflecting La Nina conditions. A Kelvin wave is also moving across the Maritime Continent, though faster than the remaining MJO signal. In the coming weeks, the MJO is forecast to remain weak, with the low-frequency signal dominating, and some influence from the Kelvin wave and tropical cyclones.

Tropical Storm Haikui formed just west of the northern Philippines, then moved westward across the South China Sea before dissipating. In the coming 2 weeks, tropical cyclone formation odds are increased over the Bay of Bengal, with a likely track to the north toward eastern India and Bangladesh. Additionally, during Week-1, there is a threat of tropical cyclone formation for the area from the South China Sea to just east of the Philippines. Over the North Atlantic, a subtropical storm is possible near 30W/30N, with a track to the northeast. Later in Week-1 and into Week-2, some models indicate generally lower pressures over the western Caribbean, though confidence in the formation of a tropical depression is low. A threat of the first tropical cyclone of the season over the Southwest Pacific is indicated in the official outlook, supported by some model forecasts, though confidence is low to moderate.

During Week-1, above average rainfall is likely along the predicted tracks of tropical cyclones. Additionally, the remaining MJO and La Nina related circulations favor above average rainfall over the Maritime Continent with some of that extending over the Coral Sea and Southwest Pacific. Suppressed convection is likely over the Central Pacific, related to the same two forcings. A stalled front is likely to support rainfall across the Caribbean and western Atlantic. Late season frontal activity is predicted over southern Brazil and Uruguay.

The signal for above average rainfall over the Maritime Continent remains in Week-2, though confidence in the western portion of the signal is lower. Below average precipitation should persist over the Central Pacific, while the Southwest Pacific is likely to receive above average rainfall.

Week-1 forecasts over Africa are made in consultation with CPCs 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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