Generally minor changes were made to the highlighted precipitation areas released earlier this week on 8/25. Across the central Pacific basin, the enhanced rainfall area was expanded northward to include Hawaii and nearby waters to the east and south. Tropical cyclones Ignacio and Jimena are tracking to the west northwest into these regions. With tropical cyclones Ignacio and Jimena forming this week it is somewhat unlikely for additional development to occur in the east central Pacific basin over the next four days as indicated by model guidance and determined in consultation with the National Hurricane Center. Consequently, the previous tropical cyclone formation hazard was removed.
The below median precipitation highlighted area in Mexico was expanded based on model guidance and enhanced rainfall is now indicated along the track of tropical cyclone Erika as it interacts with the Carribean Islands, Florida and the Bahamas over the next several days. There is high uncertainty, however, with the eventual forecast track.
For the previous Week-2 outlook, only minor changes were made to precipitation areas. The tropical cyclone hazard in the east central Pacific was lowered to moderate confidence as forecast guidance now currently indicates decreased signals in this region.
Previous discussion from 8/25
The pattern of anomalous tropical convection over the past week indicates suppressed convection across the eastern Indian Ocean to the Maritime continent as well as for most areas of the Caribbean and Central America. Enhanced convection was observed over much of the central and eastern Pacific just north of the equator and with tropical cyclones across the Northwest and north central Pacific. It was an active week for the development of tropical cyclones in the central Pacific as Tropical Storm Kilo and Loke formed.
The pattern of tropical convection continues to be dominated by ongoing El Nino conditions and areas with active tropical cyclones, namely Goni and Atsani, two very strong typhoons in the western Pacific basin. Tropical Storm Erica also very recently developed in the central Atlantic as did Tropical Depression 12 in the east-central Pacific. The MJO remains incoherent with both the RMM and CPC velocity potential based indices indicating little signal in amplitude and/or eastward propagation. Even other common subseasonal tropical variability such as atmospheric Kelvin or equatorial Rossby wave activity is generally absent.
The weak MJO activity is likely to continue for at least the next couple of weeks as little if any signal is forecast from dynamical model RMM forecasts from any of the operational centers. The MJO is not expected to play a role in the evolution of large-scale global tropical convective patterns during this outlook period. The outlook is primarily based on typical impacts associated with El Nino conditions modulated to some degree by dynamical model guidance.
Suppressed rainfall is favored for most of the Maritime continent, the Philippines and areas of the far western Pacific. Model guidance, at the current time, indicates a more quiet period for the western Pacific over the next two weeks. Drier than average conditions across the Maritime continent is consistent with El Nino conditions. The central and eastern Pacific are expected to remain very active with both enhanced rainfall and tropical cyclone development. Tropical Depression 12 is forecast to move west-northwest towards Hawaii as it strengthens (forecast to become a hurricane). During Week-1, enhanced rainfall is primarily forecast for an area from just east of the Date Line to 100W just north of the equator. However, during Week-2 impacts from favored tropical storm development and associated west-northwest tracks, increases the chances of above average raifall for the Hawaiian Islands and nearby waters.
Below average rainfall continues to be favored for areas of the Caribbean, northern South America and Central America throughout the period consistent with El Nino conditions. This highlighted area is eliminated on its northern edge due to the potential west-northwest track of Tropical Storm Erika towards Puerto Rico and then eventually the Bahamas later in the period. This potential track and a stationary front is forecast to result in above average rainfall over the southern Florida Peninsula, Bahamas and nearby waters.
A disturbance northwest of the Philipines is forecast to track north-northeast and may result in heavy rainfall for extreme eastern areas of China and parts of South Korea and southern Japan during the Week-1 period. There is also some potential for tropical development of this system, but the odds are considered somewhat low at the current time so no area is highlighted on the outlook map.
Forecasts for enhanced or suppressed rainfall across Africa are provided in collaboration with CPC's Africa Desk and are based on model forecast guidance and regional scale anomaly features.
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.
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.
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.
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.