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

Last Updated - 07.13.18 (Update)


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Global Tropical Hazards/Benefits Assessment

Global Tropics Hazards and Benefits Outlook Discussion

Updated discussion
Last Updated: 07.13.18 Valid: 07.14.18 - 07.24.18
The RMM index continues to show the active Madden-Julian Oscillation (MJO) lingering over the eastern Maritime Continent, with minimal eastward progression observed in recent days. The MJO is currently dominated by the zonal winds, with both 850-hPa and 200-hPa contributions of around two standard deviations, despite outgoing longwave radiation exhibiting minimal amplitude. Model guidance remains consistent with predicting a more progressive signal beginning in the next few days with the remainder of Week-1 being in Phase 5, while Week-2 is a combination of Phases 5 and 6 as the signal enters the West Pacific. This uptick in phase speed of the intraseasonal envelope among model guidance appears tied to Kelvin wave activity, presently near 120E, overtaking the slower intraseasonal envelope which is currently closer to 150E. Model guidance continues to hint the MJO signal will continue to be circulation driven with limited convective coupling supported at this time, despite the increasing oceanic heat content available across the Pacific associated with the anticipated transition towards El Nino later this year.

The National Hurricane Center (NHC) continues to monitor the redevelopment of Hurricane Beryl in the Atlantic off of the Eastern Seaboard, but with only a 30% chance of redeveloping into a tropical cyclone (TC) over the next 5 days the system is dropped from the forecast map. Similarly in the Pacific, the trough of low pressure currently near 12N/125W persists but is not overly organized and NHC supporting a 30% chance of TC formation that does not appear in the updated forecast here. In the West Pacific, moderate confidence continues for a pair of systems possibly developing east of Taiwan and the Philippines during the remainder of Week-1. A moderate confidence TC formation region was considered during Week-2 within the Mei-yu front in an area similar to Week-1, but the GEFS is the only forecast model bullish on this development while also having a noted false alarm bias for tropical cyclogenesis relative to other ensemble systems.

Above- and below-median precipitation areas during the remainder of Week-1 and Week-2 were updated in line with the latest CFS and ECMWF guidance. The most predominant changes are: the addition of a Kelvin wave-driven above-normal precipitation shape extending across the east Pacific during Week-2, a slightly more progressive Mei-Yu front in the West Pacific that impacts favored above-normal precipitation within the feature as well as below-normal precipitation to its south, and refinement of areas that may see above-normal precipitation with the North American Monsoon.


----- The previous discussion from July 10th follows below. -----


The RMM-based MJO index has shown an amplifying enhanced convective signal centered over the Maritime Continent during the past few days, albeit with little to no eastward propagation. The CPC upper-level velocity potential based MJO index is consistent, depicting a weak signal that has yet to propagate. The emergence of this signal is potentially tied to extratropical forcing from a Southern Hemisphere wave train that is apparent in the 200-hPa zonal wind anomaly field, with enhanced ridging centered just east of Australia and a downstream trough breaking onto the Equator near and west of the Date Line, injecting westerly anomalies aloft. The big question is whether this emerging tropical signal couples convectively and begins propagating eastward. Both the CFS and ECMWF do depict some eastward propagation of the RMM signal, with the phase speed on the slow end of canonical MJO events. Statistical tools are broadly consistent with the dynamical model MJO forecasts. Other modes of variability, including potential tropical cyclones and additional midlatitude influences, are likely to continue influencing the overall pattern. A potential MJO event emerging over the West Pacific may also play a role in the evolution of the base state towards El Nino conditions via further disruption of the Pacific trade winds. Some of the bias-corrected ECMWF RMM-index forecast ensemble members depict a high amplitude (3 standard deviations) West Pacific event, which would be consistent with a base state transitioning towards a warm ENSO event.

Two tropical cyclones formed over the Atlantic basin during the past week. Hurricane Beryl developed on July 5 as a very small circulation embedded in a broader region of disturbed weather. Due in part to its small circulation, both the intensification to hurricane status over the central Atlantic and subsequent dissipation east of the Lesser Antilles were rather abrupt. Tropical Storm Chris developed off the coast of the Carolinas near 75W, and has moved little over the past several days. A strengthening to hurricane intensity is favored by the NHC, with the storm rapidly recurving to the northeast over the next 72 hours. Little impact to land other than increased ocean swells is expected. Over the West Pacific, Typhoon Maria strengthened to Category-3 intensity on the Saffir-Simpson scale, and is forecast to pass just north of Taiwan before making landfall over eastern mainland China early in the period. Additional tropical cyclogenesis is favored over the West Pacific basin during Week-1, with a disturbance near Guam (Invest 92W) favored to develop over the next few days east of the Philippines. A second system may form over the northern South China Sea later in the Week-1 period. Further east, there is a low to moderate potential for tropical cyclone formation over the east-central Pacific well west of 120W, and southeast of Hawaii in the vicinity of enhanced ITCZ activity. Additionally, the remnants of Hurricane Beryl, or the broader disturbance in which it was embedded, have a moderate potential for redevelopment during Week-1 just east of the Bahamas. Most GFS ensemble members keep this system east of the mainland U.S., although the potential for impacts along the coast cannot be completely ruled out. During Week-2, additional tropical cyclogenesis is possible over the Northwest Pacific near or west of Guam, while the Western Hemisphere basins appear to quiet down.

Forecasts for above- and below-normal precipitation were made utilizing MJO composites for canonical Maritime Continent and West Pacific events, and a consensus of CFS and ECMWF dynamical model guidance. During Week-1, enhanced monsoon activity is anticipated across central India and Southeast Asia, with the monsoon trough extending well over the northwestern Pacific. Suppressed convection is favored to the south and north of this region across the equatorial Indian Ocean and western Maritime Continent, as well as northeastern China, the Korean Peninsula, and southern Japan. Enhanced convection is favored to extend across much of the Pacific north of the equator, although suppressed convection is favored along Mexico's southern coast, western Central America, and the adjacent waters of the far East Pacific. Enhanced monsoon activity is anticipated across the Southwest U.S., with the heaviest precipitation favored along the Arizona and New Mexico border. Additionally, a cold air outbreak may bring a period of near to below freezing temperatures to southern Brazil as far north as Parana.

The Week-2 forecast is broadly similar to the Week-1 pattern, which is consistent with a slowly evolving MJO signal. Enhanced convection is favored to extend across Southeast Asia, the South China Sea, and across much of the tropical North Pacific, which is consistent both with the intraseasonal signal and the slowly evolving base state. Suppressed convection is anticipated to continue to the south of this region, across the equatorial Maritime Continent. Suppressed convection is also favored to persist over the East Pacific, southern Mexico, and Central America, although an MJO event emerging over the West Pacific may induce Kelvin wave activity late in the Week-2 or Week-3/4 periods.

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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