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

Last Updated - 02.20.18 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 02.20.18 Valid: 02.21.18 - 03.06.18
Conditions in the tropics have continued to be influenced by the Madden Julian Oscillation (MJO) during the past week, though the footprint has weakened in comparison to previous weeks. Movement in the MJO signal has stalled since last week, remaining mostly in Phase 7, until progressing into Phase 8 in the past few days. Model guidance is in good agreement that the MJO will move through Phase 8 into Phase 1 during Week-1, possibly weakening further. Forecasts for the MJO signal moving into Week-2 are more uncertain; some models move the signal more quickly through Phase 2 and into Phase 3 during the period. All models do forecast a more significant weakening to the MJO signal in Week-2. La Nina remains active in the central and east Pacific, destructively interfering with the MJO convective envelope as it moves through the Pacific. Forecasts indicate that La Nina is likely to remain active through the winter, most likely transitioning to ENSO-neutral conditions during the spring and early summer.

Moving into the next two weeks, outlooks for tropical cyclone (TC) formation in the western Pacific and Indian Ocean are forecast to be quiet currently. There is a possibility for a TC formation in the Southwest Pacific in Week-1, though confidence remains low at the time, so it is not included on the map. Models also point to possible formation near the Philippines in the western Pacific for Week-2, though uncertainty in the strength of the system leaves confidence low.

Precipitation patterns for Week-1 loosely follow patterns for Phase 8 and Phase 1 MJO impacts; however, with the weakening signal, impacts are not forecast to be significant as the past few weeks. There are high confidence areas of below-average rainfall over the Maritime Continent and eastern Indian Ocean likely due to suppressed convection. The exception is the Coral Sea coast, for which model guidance indicates above-average rainfall. Above-average rainfall is expected for the eastern Pacific, near Hawaii, as well as near the Date Line. These patterns are typical of a Phase 8 MJO, as the convective envelope moves over the central Pacific. The central and eastern equatorial Pacific is forecast to receive below-average rainfall, consistent with impacts expected from the La Nina base state. Above-average precipitation is also forecast for Brazil and parts of the tropical Atlantic. Both model guidance and MJO impacts support this pattern.

Week-2 continues many of the patterns seen in Week-1 as the MJO is forecast to move through Phase 1 into Phase 2 for the latter part of the period. The MJO is also expected to have a dramatic weakening during Week-2, so much of the confidence in the forecast is reduced. Regions of high confidence are supported by dynamical model guidance as well as typical MJO patterns. Below-average rainfall is likely to remain over the Maritime Continent, with possible shifts eastward. Above-average rainfall is still forecast for northeast Australia, as well as the Philippines, for which model guidance shows possible TC formation. Model guidance forecasts above-normal temperatures in southeastern Australia, with anomalies up to 16 degrees C. Below-average rainfall is still forecast for the central Pacific, but the extension into the eastern Pacific has been reduced, due to the interaction with the convective portion of the MJO and the low frequency base state. Above-average rainfall is forecast to continue over Brazil and parts of the Atlantic, as well as the southwestern Indian Ocean. This is likely due to the expected re-emergence of the MJO signal in the Indian Ocean toward the end of Week-2.


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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