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HOME > Climate & Weather Linkage > Global Tropics Benefits/Hazards

Last Updated - 01.12.21 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 01.12.21 Valid: 01.13.21 - 01.26.21
The amplitudes of both the RMM-based and CPC velocity potential-based Madden-Julian Oscillation (MJO) indices increased during the past week, suggesting the initiation of a broad-scale enhanced convective envelope over the Indian Ocean. This enhancement was well forecast by both the GEFS and ECMWF over the past couple of weeks, though the timing of the observed amplification was delayed. The enhanced convection seems to be resulting from constructive interference between a Kelvin wave returning to the Indian Ocean and midlatitude wavebreaking onto the tropics that is helping to generate strong equatorial Rossby wave activity. Based on this complex method of initiation, plus the ongoing La Nina event in the Pacific, it is not clear whether sustained eastward propagation of the enhanced convection will ensue. Both the GEFS and ECMWF ensemble systems favor a fairly rapid weakening of the RMM-index as the suppressed phase of the Rossby wave begins interfering with the enhanced convection over the Maritime Continent. Towards the end of Week-2, however, many ensemble members from both models favor amplification over the West Pacific, suggesting that some Kelvin wave or remnant MJO activity will continue propagating eastward. Given the weak MJO signal during most of the forecast period, however, this outlook is based primarily on climate anomalies associated with the La Nina event, which is well coupled to the atmosphere.

No new tropical cyclones developed during the past week. Due to the aforementioned Rossby wave activity, the southern Indian Ocean has a potential for becoming quite active over the next two weeks. The Joint Typhoon Warning Center is currently monitoring two invests over the southeastern Indian Ocean, 99S, and 90S to the east of the Cocos Islands. Invest 99S has a high potential for formation during Week-1, and dynamical model forecasts indicate that the system may become an intense and long-lived tropical cyclone as it moves westward. Interests in the southern Indian Ocean, including Madagascar, should monitor updates from their local meteorological agencies. The second system, Invest 90S, has a moderate potential for formation as it nears the Cocos Islands moving westward or southwestward. Several model forecasts show this system intensifying robustly as well. During Week-2, there is a slight chance for additional tropical cyclogenesis north of Australia's Kimberley Coast, but confidence was too low to include a hazard on this week's outlook. Elsewhere, dynamical models did not indicate any consistent signals for tropical cyclone development.

Precipitation forecasts for the next two weeks are based on a consensus of bias-corrected CFS and ECMWF forecasts, and closely resemble precipitation anomalies associated with canonical La Nina events. In particular, the strong suppressed (enhanced) convective signal over the equatorial Pacific (Maritime Continent and Southwest Pacific Convergence Zone) are characteristic of La Nina. Anomalously warm sea surface temperatures north of New Guinea may result in very heavy rainfall during late Week-1 and early Week-2. Over the Indian Ocean, enhanced convection appears to be focused north and south of the Equator, with enhanced rainfall affecting southern India and Sri Lanka, and potential tropical cyclone activity bringing heavy rainfall to parts of the southern Indian Ocean.

For hazardous weather concerns during the upcoming two weeks across the U.S. please refer to your local NWS Forecast Office, the Weather Prediction Center's Medium Range Hazards Forecast, and CPC's Week-2 U.S. Hazards Outlook. Heatwave conditions are favored for the early part of the week across northern portions of Western Australia. Forecasts over Africa are made in consultation with the CPC International Desk, and can represent local-scale conditions in addition to global-scale variability.

Product Release Information

The full Global Tropics Hazards and Benefits Outlook (GTH) is released once per week every Tuesday at 1730 UTC (1830 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 and soon will be recorded.

CPC also issues an operational update of this product every Friday by 1730 UTC to further support the NWS regions. The update only spans the release period from June 1 through November 30 and a region from 120E to the Prime Meridian in longitude and from the equator to 40N in latitude. The update does not extend the time horizon of the product, but rather applies for the remaining 4 days of the previous Week-1 time period and Days 5-11 from the previous Week-2 period. This page will depict both the original and updated outlook maps as well short text outlining the forecast rationale for any changes.

Product Description

The Global Tropics Hazards and Benefits Outlook is a forecast for areas with elevated odds for above- or below-median rainfall, above- or below-normal temperatures and regions where tropical cyclogenesis is favored 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. Above(below) normal temperature forecast areas are depicted in orange and below 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:

  1. 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
  2. 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)
  3. 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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