The MJO remained incoherent during the previous week. The CPC 200-hPa velocity potential based MJO index began to show a weak signal during the past week while the Wheeler-Hendon MJO Index amplitude remained below 1.0. Continued equatorial Rossby wave activity forced by extratropical intrusions into the tropics is evident over the eastern Pacific. Two atmospheric Kelvin Waves are also impacting the circulation, with the largest impact coming over the Indian Ocean as convection there is anomalously strong. The second Kelvin wave is located over the eastern Pacific.
Dynamical model guidance has come into better agreement indicating the development of a more coherent MJO pattern later in Week-1 and into Week-2, with enhanced convection along the equatorial Indian Ocean, and suppressed convection across the western Pacific. Above-normal sea surface temperatures across the Indian Ocean suggest that conditions may be supportive for the development of enhanced convection, with the existing Kelvin wave over the eastern Pacific possibly serving as a trigger as it enters the western Indian Ocean. Considerable uncertainty remains in the forecast due to the competing influence of each of the Kelvin waves and the extratropical influence over the Atlantic Basin. The statistical models suggest only a weak MJO signal based on weak initial conditions.
Cyclone Lehar weakened quite rapidly near the west coast of India. Tropical Depression 33 formed near Guam, and is expected to become a Tropical Storm shortly. During the next two weeks, there are enhanced odds for tropical cyclone formation across the Bay of Bengal, although the confidence there is only moderate as the Bay of Bengal tropical cyclone season is winding down. Additionally, the threat of tropical cyclone formation is increased across the Southern Indian Ocean during both Week-1 and Week-2, with the Week-2 threat slightly further east than during Week-1. The increased threat rests on the assumption of an MJO developing with the enhanced convective phase centered across the Indian Ocean.
The precipitation outlook for Week-1 is based largely on recent observations and consensus from dynamical model guidance. Enhanced rainfall is forecast for most of the Indian Ocean and portions of the Maritime Continent, consistent with a developing MJO. Additionally, enhanced rainfall is likely to the east of Australia and near New Zealand later in Week-1. Enhanced rainfall is likely across the northern portions of South America from Ecuador to Venezuela due to the atmospheric Kelvin Wave early in the period and southerly displacement of the ITCZ. Suppressed convection is indicated across the South China Sea, western North Pacific, and central Pacific near the Date Line as a result of anticipated MJO activity. Anomalous westerly flow into sub-Saharan Africa should support above-average rainfall over Angola and neighboring countries.
During Week-2, the MJO is forecast to propagate eastward, bringing rains to more of the Maritime Continent and portions of the Southern Indian Ocean. Suppressed convection should remain in place over the central Pacific and over northern South America in the wake of the Kelvin Wave.
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.