The MJO remained weak over the past several days, as many observational indicators are less coherent than during March and early April, with other modes of subseasonal tropical variability evident in the tropical circulation. Despite the current weak or less coherent nature of the tropical subseasonal circulation, dynamical model MJO index forecasts indicate a strengthening signal during Week-1, with eastward propagation of enhanced convection from Africa across the Indian Ocean during Week-2. Tropical Storm Zane formed off the northeast coast of Australia and likely will impact the extreme northern portions of Australia early in the period with strong winds and heavy rainfall.
The Week-1 outlook is based on where anomalous convection is currently ongoing and likely to persist, dynamical model forecasts and statistical forecasts based on the various subseasonal modes. The forecast emergence of a stronger MJO signal over the Indian Ocean is a factor in the outlook. Above-average rainfall is favored across parts of the eastern Maritime Continent and western Pacific. This is largely due to an atmospheric Kelvin wave currently observed near 140E, and relatively weak atmospheric Rossby wave activity. Much of this area has been active over the past few days and the numerical guidance supports continued activity into Week-1. Above-average rainfall is likely from eastern, equatorial Africa to the central Indian Ocean, including extreme southern India and Sri Lanka associated with the MJO. Enhanced odds of drier than average conditions are indicated across much of Southeast Asia consistent with the suppressed phase of a strengthening MJO signal and CFS model guidance.
The Week-2 outlook is based on the evolution of the MJO from Phase 1 to Phase 2 and perhaps Phase 3 by the end of the period, modified by model guidance and taking into account uncertainty due to other subseasonal modes. Some uncertainty associated with the MJO preclude designation of high confidence areas during Week-2. Above-average rainfall is favored across parts of the central and eastern Indian Ocean, consistent with for anticipated placement of the convectively active phase of the MJO. This region could be enhanced by Kelvin wave activity as well. Other moderate confidence regions favoring above-average rainfall are located again across parts of the south-central Pacific with below-average rainfall favored across the Southeast Asia and the Philippines.
During the upcoming period, an enhanced threat of tropical cyclone formation is forecast across the southwest Indian Ocean, both Week-1 and Week-2, which is quite late in the season for potential development.
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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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