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

Last Updated - 07.19.19 (Update)


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Global Tropical Hazards/Benefits Assessment

Global Tropics Hazards and Benefits Outlook Discussion

Updated discussion
Last Updated: 07.19.19 Valid: 07.20.19 - 07.30.19
The thinking from the original update remains largely on track regarding continued weakness of the MJO's influence relative to other large-scale modes of tropical variability. What remains of the enhanced MJO envelope is likely to shift over the Indian Ocean next week, but continue to be masked by robust equatorial Rossby wave activity over the Indian Ocean and Kelvin wave activity over the Western Hemisphere. Models also support the possibility of more Kelvin wave activity ejecting from the enhanced MJO envelope, further confounding interpretation of tropical modes of variability and their associated influences on precipitation.

Resulting changes are minimal to the Week-1 outlook. The Week-1 East Pacific tropical cyclogenesis region is downgraded to moderate confidence, as it now only encompasses one system being monitored by the National Hurricane Center (NHC), which they give a 60% chance of development during the forecast period. Further west, a second area being monitored by the NHC in the East Pacific has a 20% chance of developing over the next five days resulting in it being left off the updated outlook. West Pacific precipitation was adjusted slightly in Week-1 to account for the latest forecast track of Tropical Storm Danas. Week-2 now features remarkably poor agreement between the CFS and ECMWF guidance, lowering confidence from the initial outlook even further. That said, both models continue to support TC formation potential in the East Pacific, although shifted east-southeastward from the initial outlook.

The original discussion from Tuesday, July 16th follows below.

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The Madden-Julian Oscillation (MJO) reverted to an incoherent state over the course of the past week as expected, with multiple competing modes of tropical variability serving to mask what remains of the primary MJO envelope. What remains of the MJO looks likely to shift from over Africa to the Indian Ocean during the course of Week-1, although how substantial its impacts are remains to be seen given the robust equatorial Rossby wave activity that has been observed over this basin since mid-June. Models diverge in how pronounced the MJO becomes with some downplaying the other modes of variability (e.g. the GEFS), while others continue to muddy the MJO signal (e.g. the ECMWF). Generally some hint of the MJO being in Phase 1 during Week-1 and then shifting to Phase 2 or 3 for Week-2 make it into the forecast, although confidence is low on widespread, significant MJO-driven impacts during the next two weeks.

During the past week Hurricane Barry formed over the Northern Gulf of Mexico. Barry developed from an extratropical low that drifted southeastward over the warm Gulf waters, becoming a marginal Category 1 Hurricane before making landfall over the Louisiana coastline on the 13th. Barry's primary impacts included heavy rainfall from the TC and its predecessor disturbance (totals of up to a foot or more) and a storm surge of up to 7 feet as the system came ashore. The Atlantic appears likely to return to a quiet state over the next two weeks, with attention focused instead on activity in the Pacific. In the West Pacific, the quiet year to date was interrupted by the formation of Tropical Depression 6 east of Luzon on 16th. This system is forecast to track northward with impacts to Taiwan and eastern China during the next few days as the system likely intensifies to tropical storm strength. Looking forward, the more active part of the Pacific appears to be the East Pacific, with three TCs possible over the next two weeks. During Week-1, the National Hurricane Center is monitoring a westward-moving wave near 11N/91W with a 50% chance this system develops over the next 5 days. Later in Week-1, model guidance suggests the potential for a second system developing in this general vicinity and tracking to the northwest while staying well off the Mexican coastline. Given the possibility for both systems to form in the same general area, a single region with high confidence for TC formation is given during Week-1. Later in Week-2, another TC may develop in this same area while taking a similar track to the second system from Week-1, resulting in a moderate confidence of TC formation for a similar area during Week-2.

Confidence is highest for above-normal precipitation across an arc stretching from southern India eastward across Southeast Asia through the East China Sea tied to equatorial Rossby wave activity and the forecast track of Tropical Depression 6. Across the southern Indian Ocean, confidence is also high for above-normal precipitation where low frequency conditions have favored anomalous convection. Model guidance is consistently dry across the West Pacific, despite the lack of canonical tropical modes driving this feature, but high confidence exists for below-normal precipitation anyway given the quiet 2019 tropical cyclone season for the region. High confidence also exists for above-normal precipitation across portions of northwestern South America tied to a robust tropical wave moving through the region coupled with anomalously high precipitable water observations. Persistent above-normal sea surface temperatures south of Hawaii support the moderate confidence for above-normal precipitation for this area. The suppressed phase of an equatorial Rossby wave supports a moderate confidence of below-normal precipitation stretching from eastern India through southern China. High confidence exists for above-normal temperatures across much of the eastern half of the U.S. during Week-1 tied to a robust extratropical ridge that does not appear tied to the MJO.

The enhanced (suppressed) portions of equatorial Rossby wave activity are forecast to yield high confidence of above-normal (below-normal) precipitation across Central India through Myanmar (the eastern Indian Ocean through West Pacific) during Week-2. Remaining areas of above-normal precipitation forecast in Week-2 are tied to the low frequency state (southern Indian Ocean and South Pacific) and easterly wave activity in far southern portions of the tropical Atlantic.

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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