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

Last Updated - 12.06.16 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 12.06.16 Valid: 12.07.16 - 12.20.16
The RMM-based MJO index remained weak over the past several days. The amplitude of the CPC velocity potential based MJO index has weakened as well. The pattern of tropical convection is complicated by a westward moving tropical wave over the eastern Indian Ocean, as well as Kelvin wave activity. The remnant MJO signal is likely over the Maritime Continent. Dynamical model MJO index forecasts generally depict a weak signal over the next two weeks, with some differences between the GEFS and ECMWF solutions. The GEFS develops a higher amplitude subseasonal convective signal over the eastern Indian Ocean later in Week-1 when a Kelvin wave currently entering the Eastern Hemisphere comes into phase with forecast tropical cyclone activity over the Bay of Bengal and the low-frequency signal. The ECMWF ensemble system, however, depicts a weak signal that slowly propagates the enhanced convective envelope to the West Pacific by the end of Week-2. The ECMWF solution is slightly favored, but the difference is relatively minimal in terms of areas favoring above- or below-average rainfall given the low amplitude pattern in either case.

Tropical Storm Nada formed on 29 November over the Bay of Bengal and dissipated before landfall. During Week-1, there is a high potential for new tropical cyclogenesis over the Bay of Bengal at the start of the period. Tropical cyclone formation is also possible over the West Pacific at an unusually low latitude and, if a storm forms, a northward track is likely. The GEFS and ECMWF are not in good agreement here, with the former consistently forecasting TC development over the coming days. During Week-2, tropical cyclogenesis is possible over the South China Sea and northwest of Australia. Both of these areas are indicated by the GEFS with some support from the ECMWF.

Forecasts for areas of enhanced or suppressed precipitation were based primarily on dynamical model guidance and the low-frequency base state. Enhanced convection is likely from the Bay of Bengal southeastward across the western Maritime Continent, as well as over parts of the equatorial Indian Ocean and South Pacific. La Nina conditions support suppressed rainfall across much of the tropical central Pacific, while model guidance indicates below-average rainfall across much of the Indian Ocean just north and south of the equator. Areas of enhanced rainfall are favored across Hawaii and over the West Pacific. There is also an enhanced risk of MCS activity over parts of subtropical South America.

During Week-2, suppressed (enhanced) rainfall is anticipated over the central Indian Ocean and central Pacific (far eastern Indian Ocean, the Maritime Continent, and West Pacific), reflecting the low-frequency state modulated by a weak, eastward-propagating MJO signal.

Forecast shapes over Africa are made in consultation with the International Desk at CPC, and often reflect more regional scale variability in addition to large-scale climate factors.

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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Page last modified: 6-Dec-2016 10:55 PM EST
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