The MJO remained weak during the past week with the CPC velocity potential index and the Wheeler-Hendon RMM-based index indicating the lack of a MJO signal. Dynamical models indicate a strengthening signal over the Maritime Continent and West Pacific, with little to no propagation. Statistical forecasts of the MJO indicate a continued weak signal during the next two weeks. Therefore, the MJO is not expected to influence convection or tropical cyclone activity during the next two weeks. Diagnostic tools reveal the presence of a Kelvin wave crossing Africa with other modes (Equatorial Rossby Wave) impacting the Maritime Continent.
As of 11am on 30 Sep 2014, Tropical Depression Rachel is still active over the East Pacific, with Tropical Storm Phanfone over the West Pacific. Tropical Storm Kammuri has become extratropical during the past 24 hours. During the next 2 weeks, tropical cyclone activity is likely to be enhanced over the East Pacific, and over the western North Pacific, east of 140E. The National Hurricane Center (NHC) outlooks indicated a 90% chance of formation during the next 5 days near the southern coast of Mexico. There is also a lower confidence threat of tropical cyclone formation from around 10N/130-140E, near and north of Palau. Some models are depicting a tropical cyclone over the Arabian Sea during the latter portions of Week-1, although confidence is low to moderate, at best. The western North Pacific is likely to remain active through Week-2, although the confidence decreases into Week-2. Meanwhile, tropical cyclone development is expected to remain below climatology across the Atlantic basin. Currently, NHC indicates a near 0% chance of development during the next 5 days.
The Kelvin wave moving across Africa is expected to contribute to the variability over the Indian Ocean, but likely to increase convection over the western Pacific later in Week-1. This is due to the out of phase interaction with the Equatorial Rossby Wave currently located over the Maritime Continent. The Asian Monsoon circulation is likely to be weaker during Week-1, favoring below-average precipitation across much of India and Southeast Asia. The normal monsoon retreat dates are 7-12 October for most of Southeast Asia and India. Above average rains are likely over southern Mexico along with an increased threat of tropical cyclone formation. SSTs in near the tip of Baja California are below average now, compared to being much above average earlier in the summer. That does favor less precipitation than in previous weeks for this wet region. Below average rains are likely over Central America, where drought is still plaguing some countries, especially Belize.
During Week-2, enhanced rainfall is likely over the southernmost portions of Southeast Asia and portions of the western North Pacific. Below average rains are favored over India and Central America.
Rainfall forecasts over Africa are based on local scale circulation features and produced by the CPC International Desk. For details, please see http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/africa/africa.shtml
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.