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

Last Updated - 07.01.16 (Update)


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Global Tropical Hazards/Benefits Assessment

Global Tropics Hazards and Benefits Outlook Discussion

Updated discussion
Last Updated: 07.01.16 Valid: 07.02.16 - 07.12.16
The amplitude of the MJO decreased according to the Wheeler-Hendon RMM index in recent days, while the CPC index based on the 200-hPa velocity potential depicts a continued MJO signal although at a faster eastward propagation. A strong atmospheric Kelvin Wave, progressing east across the Western Hemisphere, is likely affecting these indices. Due to this ongoing atmospheric Kelvin Wave, the evolution of the MJO during early July is uncertain. Precipitation forecasts from the latest GFS, CFS, and ECMWF models were used to modify the favored areas of above and below-median rainfall areas through July 12.

As of July 1, a broad area of low pressure is located several hundred miles southwest of Acapulco, Mexico. Environmental conditions are becoming more conducive for tropical cyclone development across the East Pacific. Therefore, high confidence exists for a tropical depression to form across this region during the next four days. The atmospheric Kelvin Wave likely contributed to initiation of convection, east of the Philippines, this week. Moderate confidence for tropical cyclone development is forecast across the West Pacific (10-15N/135-145E) during the next few days, which is supported by the latest GFS and Navy NOGAPS models.

Model guidance remains consistent that a second tropical cyclone is likely to develop by mid-July across the east Pacific. Due to the excellent model consistency and improving environmental conditions, confidence for tropical cyclone development is increased to high for the east Pacific from July 6 to 12. Since the models have trended towards a more westward track of the tropical cyclones across the east Pacific, above-median rainfall is less likely across the Gulf of California and is removed from the previous outlook.

A strong subtropical ridge is likely to result in above-normal temperatures and the potential for excessive heat (maximum daily heat index values of 110 degrees F, or more) across southeast Texas through July 12. The subtropical ridge is expected to expand east by July 6 and lead to above-normal temperatures and associated excessive heat (maximum daily heat index values of 105 to 110 degrees F, or more) across the eastern Carolinas, southeast Georgia, and northeast Florida.


The previous discussion released on June 28 follows.


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A robust MJO signal continued during the past week according to multiple diagnostic tools along with the RMM and 200-hpa Velocity Potential indices. The propagation of the MJO recently slowed as it shifted to the western Maritime Continent and the OLR anomaly field indicates an atmospheric Kelvin wave crossing the Date Line. Current satellite imagery indicates an axis of convection oriented from the Arabian Sea southeast to the Maritime Continent which is typical of a mature MJO signal during the Northern Hemisphere summer. Tropical Cyclone 2A developed across the Arabian Sea on June 27 and is forecast to dissipate during the next 48 hours. Dynamical model forecasts indicate eastward propagation of a MJO signal into early July, but an atmospheric Kelvin Wave and potential tropical cyclones across the east Pacific are likely influencing the RMM index.

The precipitation outlook during Week-1 is based on CFS and ECMWF model guidance, MJO precipitation composites for Phases 5 and 6, and influence from atmospheric Kelvin Wave crossing the Western Hemisphere. Above-median rainfall is favored from India southeast to southern China and Vietnam. Although there is an elevated risk of tropical cyclone formation across the South China Sea, confidence is too low to depict an area on the map. Below-median rainfall is expected to develop across the eastern Indian Ocean and the western Maritime Continent as convection begins to shift north during the next week. A small region of above-median rainfall is also forecast across the Arabian Sea, associated with the ongoing tropical cyclone. The evolving low-frequency state favors below-median rainfall across parts of the western Pacific. Model guidance generally supports above-median rainfall across the eastern Pacific and remains consistent that a tropical cyclone develops late in Week-1, originating from a westward-moving tropical wave now over Central America.

During Week-2, the remnant MJO signal is expected to result in above-median rainfall across parts of the Bay of Bengal, northern India, and eastern Pakistan, while below-median rainfall expands north to include Sri Lanka and southern India. Below-median rainfall is forecast to persist across parts of the western Pacific although model guidance differs on the most favored area. If the MJO signal remains robust, enhanced convection is likely to intensify across the eastern Pacific later in Week-2. Forecast confidence for this outcome is limited, considering that many of the dynamical model forecasts depict a decrease in the amplitude of the MJO signal. The GFS model remains consistent with an elevated risk of another tropical cyclone to form during Week-2 across the eastern Pacific. The moderate confidence for above-median rainfall across parts of northwest Mexico, the Gulf of California, and Baja Peninsula is related to the likelihood of tropical cyclone activity in the east Pacific during the next two weeks and the increasing potential for an enhancement of low-level moisture.

Forecast 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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Page last modified: 29-May-2016 10:25 AM EDT
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