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

Last Updated - 05.22.18 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 05.22.18 Valid: 05.23.18 - 06.05.18
The enhanced phase of the MJO continued its eastward propagation from Africa to the western Indian Ocean during mid-May, while the suppressed phase became centered over the Pacific Ocean. According to the RMM index, the MJO has the same amplitude in Phase 2 compared to five weeks ago. Although there is low to moderate spread on the amplitude of the MJO during the next two weeks, the MJO is expected to continue to propagate east from the Indian Ocean to the Maritime Continent.

An equatorial Rossby wave contributed to enhanced convection and helped to initiate Tropical Cyclone Sagar over the far western Arabian Sea on May 16. Sagar made a rare westward track through the Gulf of Aden and resulted in heavy rainfall and flooding across northern Somalia and coastal Yemen. Sagar eventually dissipated as it tracked over Ethiopia. A second tropical cyclone (2A) formed a few days later across the western Arabian Sea. This tropical cyclone is forecast to strengthen during the next 72 hours and track north, with a landfall in Oman or Yemen later in Week-1.

As the enhanced phase of the MJO crosses the Indian Ocean, the large scale environment favors tropical cyclone (TC) development across the Bay of Bengal during Week-1. Although the chance of TC development may linger into Week-2, the onset of the Southwest Monsoon across this region is expected to be a limiting factor. Elsewhere, a broad surface low is centered east of Belize. Although strong upper-level winds and dry air aloft are currently disrupting any organization, chances for TC development increase once this system lifts north into the central or eastern Gulf of Mexico. Large model spread continues on whether a TC develops and its subsequent track. The deterministic 0Z ECMWF model (May 22), which is the most consistent solution, indicates a closed surface low progressing to the central Gulf Coast this weekend and then becoming nearly stationary across the Southeast U.S. early next week. Regardless of TC development, heavy rainfall is likely across the Cayman Islands, western Cuba, Florida, and parts of the Southeast through Week-1. A weakness in the subtropical ridge and anomalous low-level moisture support a continuation of above-average rainfall along the central and eastern Gulf Coast into the beginning of June. Areas east of the Apalachicola and Chattahoochee Rivers have received locally more than 8 inches of rainfall during the past 30 days and are prone to flooding with any additional heavy rainfall.

The precipitation outlook during the next two weeks is based on MJO composites for phases 2 through 4 along with guidance from the CFS, ECMWF, and GFS models. These tools favor above-normal rainfall shifting from the Indian Ocean to the western Maritime Continent and West Pacific during the next two weeks. Increased chances for below-average rainfall are expected across southeast China, Taiwan, and the northern Philippines during Week-1, with the most likely area for below-average rainfall shifting to the East Pacific and parts of Central America during Week-2. An above-normal temperature hazard is posted for parts of Southeast Asia where the GFS model indicates maximum temperatures averaging more than 8 degrees C above normal and exceeding 35 degrees C.

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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