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

Last Updated - 08.09.22 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 08.09.22 Valid: 08.10.22 - 08.23.22
Consistent with the previous model solutions, the Madden Julian Oscillation (MJO) continues to be ill-defined during the past week which is reflected in CPCs velocity potential anomaly based MJO index as well as RMM observations showing a low amplitude signal over the western Pacific. Looking ahead, there is fair agreement in dynamical models depicting a fast eastward propagation of the intraseasonal signal across the Western Hemisphere and reaching the Indian Ocean, though several RMM forecasts predominantly maintain a low amplitude signal (remaining within the RMM unit circle) during the next two weeks. The rapid phase speed of the model solutions are suggestive of a convectively coupled Kelvin wave projecting onto the RMM index as it crosses the Pacific, which is supported by objective wavenumber-frequency filtering of upper-level velocity potential forecast fields. However, an eastward propagating Kelvin wave reaching the Eastern Hemisphere may incite a more coherent MJO over the Indian Ocean, as depicted by some models (CFS, BOM) later in August. In the absence of a coherent MJO, at least through the middle of August, other modes of variability are more likely to be the primary contributors to tropical precipitation as well as tropical cyclone (TC) development in the Pacific and Atlantic.

During the past week, one TC formed in the global tropics. In the eastern Pacific, TC Howard formed on 8/6 and strengthened to a category 1 Hurricane to the southwest of Cabo, Mexico. The National Hurricane Center (NHC) expects Howard to begin weakening under the influence of cooler sea surface temperatures and degenerate into a post-tropical cyclone over open waters later this week. Its proximity to the Gulf of California may trigger a gulf surge event and bring ample amounts of moisture into the Desert Southwest where enhanced precipitation amounts are favored during week-1 across much of the western CONUS.

For the next two weeks, there are several areas of interest for potential TC development. In the eastern Pacific, the NHC is monitoring a trough of low pressure to the southwest of Mexico with a 60% chance of formation during the next five days. Given the aforementioned Kelvin wave activity favored to traverse the Pacific, and support from the model guidance depicting an area of deepening low pressure later this week, a high confidence area for TC formation is posted in the wake of TC Howard. Continued TC activity in this region of the eastern Pacific may initiate another Gulf of California surge event and reinforce an enhanced moisture regime as part of the North America monsoon circulation later in the period. Farther west, the Central Pacific Hurricane Center (CPHC) continues to monitor a tropical wave to the south of Hawaii with a 30% chance of formation during the next five days. Chances of development have decreased since earlier this week and there is not enough confidence to include a corresponding TC area in the outlook. However, increased precipitation amounts and elevated winds are possible for parts of Hawaii early in week-1 associated with this disturbance as it tracks westward away from the state.

Across the Atlantic, the NHC continues to monitor a tropical wave in the Main Development Region (MDR) with a 30% chance of formation during the next five days. While models favor some deepening of low pressure in the near-term tied to this wave, environmental conditions are expected to become less conducive for development by this weekend, prompting no corresponding TC area for week-1 in the MDR. Later in the period, one or more easterly waves propagating over West Africa remain favored in ensemble guidance, where there is also multi-model agreement indicating Rossby wave activity and enhanced convection in the OLR anomaly fields over the tropical Atlantic. While some probabilistic TC tools are less supportive of TC potential in the MDR, a moderate confidence area is posted over the MDR for week-2, which coincides with a sharp climatological uptick in TC activity over the Atlantic by mid-August. Should the MJO show better signs or organization over the Indian Ocean later in August, this also historically favors increased chances for TC development in the Atlantic basin.

In the eastern Hemisphere, the JTWC is monitoring a disturbance with a high chance of formation in the South China Sea during the next day or so, and a high confidence area of TC formation in the outlook for week-1. Due to its proximity to land, locally heavy precipitation amounts and high winds are possible over parts of Vietnam and China early in the period. Farther east, the JTWC is also monitoring an area of convection over the northern Philippine Sea that has shown better signs of organization recently. A moderate confidence area is posted where there is increased support in the latest GFS and ECMWF deterministic solutions favoring the development of a closed low during the next day or so. Beyond week-1, conditions are largely expected to be quiet in the western Pacific. The deterministic GFS continues to favor TC formation in the Philippine Sea next week, though this is much less supported in other model solutions and tools resulting in no TC related areas in the western Pacific. Across the northern Indian Ocean, probabilistic TC tools continue to signal elevated chances of development in the Arabian Sea during week-1. Although TC formation is possible, no TC areas are issued due to an increasingly unfavorable shear environment associated with the Indian monsoon circulation. Regardless of formation, enhanced precipitation amounts are favored across portions of northwestern India and Pakistan.

For hazardous weather concerns in your area during the next two weeks, please refer to your local NWS office, the Medium Range Hazards Forecast from the Weather Prediction Center (WPC) and the CPC Week-2 Hazards Outlook. Forecasts issued over Africa are made in coordination with the International Desk at CPC.

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 at 2 PM local Eastern Time 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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