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

Last Updated - 09.17.19 (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
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Below Average Temperatures KMZ / KML / SHP KMZ / KML / SHP

Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 09.17.19 Valid: 09.18.19 - 10.01.19
Several moving pieces make up today's GTH forecast. Right now there is both a Kelvin wave and an equatorial Rossby wave in the Central Pacific. These waves have well-defined circulations around the equator, but their associated convection is about 5-10 degrees north of the equator. This convection will spread out as the waves separate and continue eastward and westward respectfully.

The Kelvin wave is likely to enhance convection as it moves over the East Pacific and North Atlantic during late Week-1 and Week-2, which often leads to increased probabilities of tropical cyclogenesis. We have therefore posted high risk hazards for tropical cyclone development in the eastern Pacific and North Atlantic during both Weeks-1 and 2, as well as several above-normal rainfall hazards associated with these waves. The synoptic set-up over North America and the North Atlantic will play a key role in determining the tracks of any TCs that develop in either basin and interested parties are encouraged to consult their local NWS Offices and the National Hurricane Center.

The equatorial Rossby wave is likely to provide a similar enhancement to the convective state of the Indian Ocean (IO), which may aid in the development of a positive Indian Ocean Dipole (IOD) event. The IOD is an El Nino-esque phenomenon in the IO that often appears during Autumn. Its positive phase is characterized by anomalously warm temperatures and active convection over the western IO and anomalously cold temperatures and suppressed convection over the eastern IO. This set up also features a miniature Walker-esque Circulation characterized by anomalous easterlies at the surface and anomalous westerlies aloft.

The CFS is strongly hinting at this sort of circulation developing during the next two or three weeks. This situation would explain the recent proclivity of the models to create a stationary MJO signal over the Indian Ocean since there are so many similarities between the MJO Phase 1 and the positive phase of the IOD. Due to this set up, we are not particularly confident that the MJO will play a significant role in the GTH forecast during the next two weeks, but it's possible that the IOD will. Today's forecast includes a moderate risk of above normal rainfall over parts of the western IO during Week-2 and this probability may increase if the IOD evolves in accordance with the CFS.

The Central Pacific Hurricane Center is also watching a region of potential Tropical Cyclone development just west of Hawaii. We have posted a moderate risk of TC development in this area. Users are advised to monitor the regular updates from the CPHC over the next several days.

There is a high risk for above normal rainfall over eastern Texas and southwestern Louisiana during Week-1 associated with Tropical Storm Imelda in the Gulf of Mexico. This rainfall could lead to flooding and interested parties should consult their local NWS office for the latest information.

Elsewhere, we are monitoring a small area of potential tropical cyclone formation northeast of Taiwan in Week-1 associated with a band of northward moving convection that is reminiscent of a summer MJO event. 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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