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

Last Updated - 12.05.17 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 12.05.17 Valid: 12.06.17 - 12.19.17
The MJO signal discussed in the previous week's outlook has continued to develop an area of enhanced convection over the Maritime Continent. The OLR anomalies depict an eastward propagation of the envelope of enhanced convection, starting in late November. Forecasts of the RMM-based MJO indices show a decrease in amplitude as the signal shifts eastward from the Maritime continent in Phase 5 pattern to the Western Pacific and into Phase 6 over the next two weeks. This is most likely due to destructive interference from a Kelvin wave that will slow propagation of the pattern. With the La Nina event in the Pacific, the low frequency base state will also destructively interfere with the area of enhanced convection as the MJO pattern moves across the Pacific. The upper-level fields show an apparent wave-1 pattern, with only some noise over the Indian Ocean, most likely due to tropical disturbances. Models show the MJO signal rebounding in late Week-2 and continuing into the Western Hemisphere. Statistical guidance supports the evolution seen in the dynamical forecast guidance.

There are a few areas of possible tropical cyclone (TC) formation over the next two weeks. Model guidance shows probable formation in the Bay of Bengal, as well as the Northwest Pacific for Week-1. Dynamical guidance shows uncertainty for the forecast tracks. Another area of interest is in the southwestern Indian Ocean. For Week-1, there is a possible formation in the Mozambique Channel supported by the models. Later, in Week-2, the area of formation highlighted by the models is northeast of Madagascar. Statistical guidance and some dynamical tools also showed the Coral Sea as an area of interest for TC formation. However, the low-pressure system did not organize well in the model guidance and looks to be part of an existing larger trough.

Precipitation patterns for week 1 are largely supported by the ongoing MJO signal, as well as tropical cyclone activity. The enhanced area of convection is expected to bring above-average rainfall to parts of the Maritime Continent, as well as the western Pacific. At the beginning of the period, remnants of TC Ockhi are expected to bring heavy precipitation to western Indian coast, northwest of Mumbai. The Bay of Bengal is likely to be affected by the possible TC, land falling either in India or parts of Bangladesh and Myanmar, depending on the timing of the recurvature. In the southwestern Indian Ocean, possible TC activity supports enhanced rainfall. In the Atlantic, above-average rainfall is likely to occur from a frontal intrusion. Cooler temperatures are forecast to affect the Gulf Coast region, as well as parts of Florida and Northern Mexico. Below-freezing temperatures are possible in some of the central Gulf Coast region. Above-average rainfall in South America, moving over Brazil, is supported by dynamical model guidance. Below-average rainfall is expected in the central Pacific, consistent with current La Nina state. The enhanced suppression over the Indian Ocean and western Maritime continent is consistent with the MJO pattern.

For Week-2, patterns are similar to those seen in Week-1, though shifted eastward with the propagation of the MJO event. In the northwest Pacific, the area of above-average rainfall extends further into the Pacific, due to eastward shift of the area of enhanced convection, as well as the effects of TC activity. Suppressed convection is favored to remain in parts of the Indian Ocean and moving over parts of the Maritime Continent. In South America, the area of above-average rainfall moves over Brazil and shifts to the northwest. Impacts from current and forecast MJO activity are likely to favor anomalous troughing over the central and eastern United States through the end of the month, supported by the Phase 6 and 7 lagged MJO composites.

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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