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Global Tropics Benefits/Hazards
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| Global Tropics Hazards and Benefits Outlook |
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Global Tropics Hazards and Benefits Outlook Discussion |
| Last Updated: 10.01.13 |
Valid: 10.02.13 - 10.15.13 |
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The MJO remained active during the previous week, with propagation across the western Pacific Ocean. Positive OLR anomalies associated with enhanced precipitation were observed across the South China Sea and much of the western Pacific, while suppressed convection was evident over much of the northern Indian Ocean, South Asia, and the western Maritime Continent. Suppressed convection was also observed over the Caribbean Sea and Gulf of Mexico. The 200-hPa velocity potential anomalies continue to exhibit a coherent Wave-1 structure, with areas of large scale anomalous ascent centered over the Pacific Ocean. The Wheeler-Hendon MJO Index currently has amplitude near phases 5 and 6, with day-to-day eastward propagation of the index slowed by robust tropical cyclone activity over the western Pacific. The CPC MJO Index, which is based on the 200-hPa velocity potential anomalies, depicts a clearer eastward propagation of the signal.
Typhoon Wutip formed in the South China Sea on 26 September and made landfall over Vietnam with 90-kt sustained winds. On 30 September, Tropical Storm Sepat developed south of Japan, and recently turned northward in the process of recurving east of Japan. Also on 30 September, Tropical Storm Fitow developed east of the Philippines, and is currently forecast to strengthen into a typhoon as it moves west-northwestward. As the main MJO convective envelope has propagated eastward over the Pacific, the continued tropical cyclone activity over the far western Pacific has exerted some destructive interference on the MJO signal, which is evident in the Wheeler-Hendon MJO Index and on Hovmoller plots of OLR anomalies. On 29 September, Tropical Storm Jerry formed in the north-central Atlantic, far from land.
Dynamical model forecasts of MJO evolution depicted on the Wheeler-Hendon Index depict a range of solutions, with the GFS weakening the signal, and the UKMet model continuing a robust eastward propagation. The ECMWF also depicts a continued eastward propagation of the MJO signal, albeit more slowly than the UKMet. Statistical models such as the Constructed Analog also favor additional eastward propagation. Based on current observations and several dynamical models, continued propagation of the MJO is anticipated during the upcoming two week period, with an evolution through phases 6 and 7 possible.
The precipitation outlooks are based on MJO composites and input from both the GFS and CFS models. Enhanced rainfall is favored over the western Pacific during Week-1, extending from the Philippines southeastward towards the equator, north of the Solomon Islands. Suppressed activity is anticipated across South Asia, the eastern Indian Ocean, and the western Maritime Continent. During Week-2, enhanced rainfall is forecast to spread eastward towards the equatorial Date Line, with suppressed convection overspreading the remainder of the Maritime Continent.
Continued tropical cyclogenesis is favored across the western Pacific basin, with decreasing confidence during the Week-2 period. A tropical disturbance in the western Caribbean Sea may develop slowly as it moves northwestward into the eastern Gulf of Mexico. Regardless of development, the system has the potential to produce widespread heavy rainfall over Cuba, parts of Mexico, and the Gulf Coast of the United States during the upcoming week. Several runs of the GEFS ensemble forecast indicate the possibility of additional cyclogenesis in the Caribbean during the Week-2 period. As the MJO propagates across the Pacific, atmospheric Kelvin Waves are sometimes generated and can enhance chances for tropical cyclone formation over the eastern Pacific; however, little Kelvin Wave activity has been observed and current atmospheric conditions are not conducive for development over the eastern Pacific.
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Product Release Information
The Global Tropics Hazards and Benefits Outlook is released once per week every Tuesday at 1530 UTC (1630 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.
Product Description
The Global Tropics Hazards and Benefits Outlook is a forecast for areas with elevated odds for above- or below-median rainfall and regions where tropical cyclogenesis is favorable or unfavorable 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. 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:
- 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
- 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)
- 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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