Following a brief period of an active MJO during early May, the MJO became less coherent recently as the enhanced phase advanced east of the Maritime Continent. Short-lived Tropical Storm Alvin developed across the eastern Pacific Ocean, while Tropical Cyclone Mahasen made landfall in Bangladesh during the past week.
Dynamical model MJO index forecasts indicate a weak signal during Week-1 which is partly attributed to interference from other tropical subseasonal variability. Beyond Week-1, models indicate renewed organization with the enhanced phase across the Western Hemisphere and Africa.
The Week-1 outlook is based primarily on anomalous convection associated with subseasonal modes of variability and dynamical model forecasts. The suppressed phase of an equatorial Rossby wave favors below average rainfall across the central Indian Ocean, while dynamical model forecasts indicate below average rainfall across the Philippines. Anomalous low-level convergence is expected to result in below average rainfall across western Africa. An atmospheric Kelvin wave elevates the chances for tropical cyclone development across the East Pacific. Convection is expected to increase over
the eastern Pacific and Central America due to the aforementioned Kelvin wave and the expected enhanced phase of the MJO organizing over the Western Hemisphere by the end of Week-1.
The Week-2 outlook is based on the expectation of a renewed organization of the MJO with its enhanced phase across the Western Hemisphere and Africa. Although dynamical MJO index forecasts differ on the exact evolution of the MJO signal, models generally agree on the enhanced phase of the MJO centered over the Western Hemisphere. Below average rainfall is expected to continue across the Philippines and expand east across the western Pacific Ocean. The Indian Ocean, south India, Sri Lanka, and western Africa are expected to become more convectively active which is consistent with MJO precipitation composites. Above average rainfall is likely to persist across the eastern Pacific Ocean, Central America, and shift east into the western Caribbean Sea. Warmer than normal SSTs and enhanced convection maintains elevated chances for tropical cyclone development across the eastern Pacific Ocean. A large scale ridge predicted over the southern CONUS and Gulf of Mexico during Week-2 is expected to reduce wind shear and provide favorable conditions for tropical cyclone development across the northwestern Caribbean Sea. Due to the reduced wind shear in an area of enhanced convection, the development of an early season tropical cyclone is favored for the northwest Caribbean Sea. The GFS model has been consistent in developing a potential tropical cyclone in the northwestern Caribbean Sea in early June.
|
|
|
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.
|
www.nws.noaa.gov 
