The MJO remained weak during the past week as indicated by the RMM Index and the CPC velocity potential based index. There continues to be some evidence of an eastward propagating intraseasonal signal, apparent in the evolution of an envelope of suppressed convection over the western Pacific and enhanced convection over the Indian Ocean. Other coherent modes of subseasonal convective variability, including pronounced Rossby Wave activity, are interfering with the intraseasonal signal. Tropical cyclone and monsoonal activity are also playing roles in the tropical convective pattern. There is considerable spread among the dynamical model MJO Index forecasts, with some models indicating increasing amplitude over the Western Hemisphere with no eastward propagation, and other models weakening the signal. Impacts from forecasted tropical cyclones or other evolving subseasonal modes are likely complicating the RMM Index evolution. Statistical models are generally unsupportive of robust canonical MJO activity. Based on recent observations and the dynamical and statistical model solutions, the MJO is not anticipated to play a large role in the evolution of the tropical convective pattern during the next two weeks, although the intraseasonal signal may contribute to continued suppressed (enhanced) convection over the West Pacific (Indian Ocean).
Hurricane Karina and Tropical Storm Lowell developed over the eastern Pacific on 13 August and 18 August, respectively. Karina weakened to tropical storm strength while moving on a westward track, and is forecast to continue moving slowly westward during the next several days before recurving rapidly northeastward, remaining well east of Hawaii. NHC forecasts bring Lowell on a northwesterly track well west of the Baja Peninsula during the next five days. The eastern Pacific is anticipated to remain extremely favorable for development, and late August is a climatologically active period for the basin. Therefore, there is a high potential for additional tropical cyclogenesis during the upcoming two weeks. Dynamical model ensembles cluster tropical cyclone tracks closer to the Mexican coast than recently observed tracks.
Over the Atlantic, a pair of tropical waves are moving westward east of the Lesser Antilles. There is a possibility for one of these waves to develop during the next several days. Additionally, dynamical models indicate a low to moderate potential for additional easterly waves emerging over the Atlantic later during Week-1 or during Week-2 to develop into tropical cyclones near or west of the Cape Verde islands. Based on these model solutions as well as a forecasted relaxation of recent large scale unfavorable conditions over the eastern Atlantic, a moderate potential for tropical cyclogenesis is indicated over the Atlantic MDR during both Week-1 and Week-2. Additionally, some model forecasts indicate the presence of a stalled frontal boundary over the Gulf of Mexico or southeastern CONUS, which can occasionally trigger tropical cyclogenesis closer to the U.S. coast.
During Week-1, interactions between the weak intraseasonal signal and Rossby Wave activity over the Maritime Continent favor suppressed convection over a large area extending from southeastern Asia through the west-central Pacific, including the Philippines. These signals also favor decreased West Pacific tropical cyclone activity. Enhanced convection associated with Kelvin Wave activity or the intraseasonal signal is forecast over parts of the Indian Ocean and southern India. Widespread enhanced convection is anticipated over the eastern Pacific, partly associated with ongoing and forecasted tropical cyclone activity. An active African monsoon is forecast to contribute to enhanced convection over western Africa and increased easterly wave activity over the eastern Atlantic.
During Week-2, the CFS and GFS indicate a potential for enhanced convection over the eastern Indian Ocean and western Maritime continent, possibly due to Kelvin Wave activity or the slower evolution of the weak intraseasonal signal. Suppressed convection is anticipated to continue across the Philippines and western Pacific, with enhanced convection due to tropical cyclone activity and the evolving low frequency ENSO state favored over the eastern Pacific.
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.