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

Last Updated - 07.29.16 (Update)

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Tropical Cyclone Formation KMZ / KML / SHP KMZ / KML / SHP
Upper Tercile Precipitation KMZ / KML / SHP KMZ / KML / SHP
Lower Tercile Precipitation KMZ / KML / SHP KMZ / KML / SHP
Above Average Temperatures KMZ / KML / SHP KMZ / KML / SHP
Below Average Temperatures KMZ / KML / SHP KMZ / KML / SHP

Global Tropical Hazards/Benefits Assessment

Global Tropics Hazards and Benefits Outlook Discussion

Updated discussion
Last Updated: 07.29.16 Valid: 07.30.16 - 08.09.16
The overall pattern of tropical variability has evolved as expected over the past few days, with destructive interference occurring between the MJO signal and low-frequency variability and atmospheric Kelvin waves. The enhanced phase of the MJO is now over the Maritime Continent, though lower-frequency variability over Africa and a Kelvin wave over the eastern Pacific serve to disrupt the coherent pattern of MJO-related variability. The robust wave-1 velocity potential structure has weakened substantially this week, and dynamical model forecasts diverge in their respective solutions over the next two weeks.

A few important changes are made in the Friday update with respect to forecast tropical cyclone (TC) formation from July 30 to August 2. A high risk of TC formation is now indicated over the East Pacific, associated with a convectively coupled Kelvin wave. A low risk of TC formation is forecast later over the East Pacific, but conditions are generally forecast to become less favorable with time. Atmospheric conditions appear favorable for some development of a tropical disturbance over the tropical Atlantic early in the period, with a moderate confidence indicated. Over the West Pacific, a tropical depression has formed east of the Philippines, forecast by the Joint Typhoon Warning Center to track across the far northern Philippines before taking aim at southeastern China as a weak typhoon. Additional TC formation is likely farther north over the West Pacific, associated with persistent troughing in that region. This system is expected to form by early next week, and a second system could develop over the same region later in the week. During the later period, there is a low risk of TC formation over the western Caribbean and Bay of Campeche.

Some changes were made with respect to areas favoring above- or below-average rainfall in accordance with the latest model guidance from the CFS and ECMWF.

The original forecast discussion follows:

The MJO has been active over the past week, with both the RMM and CPC velocity potential indices showing the enhanced phase moving over the western Maritime continent. In fact, by examining the time-longitude diagrams of the different variables at play, as well as the RMM phase diagram, we can say with some confidence that the MJO has been a significant component of subseasonal tropical variability for much of the summer. Today’s dynamical model guidance has come into somewhat better agreement, with the MJO forecast to propagate across the Maritime continent over the next one to two weeks. However, interference with other patterns of variability, including the slowly-evolving base state, increases uncertainty, especially with respect to forecast regions of enhanced and suppressed rainfall.

During the last week, Tropical Storm Frank and Hurricane Georgette formed over the East Pacific. Both are forecast to weaken over the next couple of days as they drift generally westward. Currently, the accumulated cyclone energy in the eastern and central Pacific is 237 percent of normal, and there is a moderate chance of tropical cyclone (TC) formation during the next week in this region, associated with a convectively coupled Kelvin wave. Beyond that, however, it appears that the East Pacific will become less active as the suppressed phase of the MJO propagates across the Western Hemisphere. The western North Pacific basin is at 40 percent of normal ACE for this time of year, and there is little support from the various model guidance for a broad increase in activity over the next two weeks. That said, Tropical Storm Mirinae formed over the South China Sea, and TC formation is likely east of the Philippines during Week-1. In the Atlantic basin, some models are indicating an increase in the chances for tropical cyclone formation during late Week-1 or early Week-2, though this threat is best classified as low potential for the time being. This will be revisited in the Friday update.

Enhanced convection is forecast from parts of Southeast Asia, through the Maritime Continent, into parts of the South Pacific during Week-1. This signal is broadly consistent with ongoing and forecast MJO activity, as is the tendency toward below-average rainfall across parts of the tropical Indian Ocean. Model guidance and the low-frequency state strongly favor below-average rainfall across parts of the central and western equatorial Pacific. A subtropical low could break off from the midlatitude flow over the North Pacific, increasing the odds of above-average rainfall. There is a low probability that this system could transition to a tropical cyclone later in Week-1 or Week-2.

During Week-2, there is less coverage due to increased uncertainty. Only the regions in which the ECMWF and CFS agree are highlighted; these regions are somewhat consistent with eastward propagation of the MJO signal and the low-frequency dry signal forecast over the central Pacific.

Forecasts over Africa are made in consultation with CPCs 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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