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GTH Outlook Map and Data
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Last Updated -
05/13/25
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GTH Outlook Discussion
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Last Updated -
05/13/25
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Valid -
05/21/25 - 06/03/25
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During the past few days, the spatial structure of upper-level velocity potential anomalies exhibited a coherent Wave-1 structure, consistent with organized intraseasonal MJO activity with an enhanced convective phase centered over the Pacific. This structure has projected well onto the CPC MJO index which is based on the upper-level velocity potential field. Other fields, such as zonal wind anomalies at both the upper and lower levels of the troposphere and the OLR anomalies are less coherent and inconsistent with robust Pacific MJO activity. Additionally, eastward propagation of this upper-level feature has not been established, and it materialized almost instantaneously rather than evolving with robust convection. The RMM-based MJO index remains within the unit circle, reflecting the incoherent pattern overall. Therefore, it is likely that the organized structure in the upper-levels is due more to the superposition of other modes of variability, including Kelvin wave activity crossing the Pacific and Rossby wave activity over the West Pacific and Maritime Continent. Dynamical model MJO index forecasts exhibit considerable spread in their solutions, with the ECMWF generally showing a weak and incoherent evolution, and the GEFS showing a greater potential for more robust MJO evolution, but with significant differences in the placement of the anomaly signatures among the ensemble members. Therefore, with a highly uncertain MJO pattern and ENSO neutral conditions persisting across the Pacific, there are little coherent subseasonal signals present to guide the outlook over the next few weeks.
One tropical cyclone developed during the past week, a late season depression (TD-32P) that briefly formed north of the Gulf of Carpentaria. During Week-2, the potential presence of the monsoon trough as a development source along with good support from dynamical model guidance depicting potential tropical cyclogenesis merits the inclusion of a tropical cyclone formation area in the northwestern Pacific, extending from near the Philippines to just south of Guam. There are some indications that a tropical cyclone formation is possible over the Bay of Bengal; however, the evolution of this potential feature is uncertain, and a monsoon low may develop in the area instead. During Week-3, a 20-percent chance for tropical cyclogenesis continues across the Northwest Pacific. Dynamical model guidance is a bit less supportive of formations overall, but development is still possible, especially early in the period in the vicinity of the Philippines. Elsewhere, potentials remain under 20-percent across the other basins; however, there is a slight potential for development over the East Pacific, should a Kelvin wave passage help weaken the shear over the region and provide a period of enhanced convection.
Given the weak seasonal and subseasonal tropical signals, the forecast for above- and below-normal precipitation leans heavily on a skill weighted consensus of operational dynamical model guidance. The strongest remaining low-frequency signal favors persistent enhanced convection across the Maritime Continent, due in part to above-normal ocean temperatures in the vicinity. Dynamical model forecasts generally support a robust onset of the South and Southeast Asia monsoon, with enhanced chances for above-normal precipitation extending during both Week-2 and Week-3 across much of India, the Bay of Bengal, and Southeast Asia. Across the Pacific, enhanced precipitation is favored just northwest of Hawaii, while a drier signal is favored to persist to the south, possibly extending as far north as the Big Island. Suppressed convection is favored during Week-2 across Central America, southern Mexico, and portions of the Caribbean and Gulf of America, with a potential switch towards a wetter signal across the East Pacific basin in Week-3. Temperature outlooks are based on the dynamical model consensus tool, as well as official forecasts for the contiguous United States during Week-2. Notably, enhanced chances for hazardous heat extend across portions of central South America despite the time of year, with maximum temperatures exceeding 35 degrees C on multiple days during the outlook period. For hazardous weather concerns in your area during the next two weeks, please refer to your local NWS office, the Medium Range Hazards Forecasts produced by the Weather Prediction Center, and the CPC Week-2 Hazards Outlook. Forecasts issued over Africa are made in coordination with the International Desk at CPC.
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Product Release Information
The Global Tropics Hazards 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 Google Meet) open to all stakeholders where the latest conditions and the newly
released outlook are shared with the opportunity to ask questions. Folks that are interested in learning more or attending these briefings should contact
Jon.Gottschalck@noaa.gov, Scott.Handel@noaa.gov, Adam.Allgood@noaa.gov and Nicholas.Novella@noaa.gov for the required information. Each weekly outlook and GTH release briefing is
Archived and available on the website.
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Product Description
The Global Tropics Hazards Outlook is a probabilistic forecast for areas with elevated probabilities for above- or below-median rainfall, above- or below-normal
temperatures and regions where tropical cyclogenesis is favored for the upcoming Week-2 and Week-3 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 brown respectively. Above (below) normal temperature forecast areas are depicted in orange and blue respectively. Favored areas for tropical
development are shown in red. Three probability intervals are indicated for precipitation and temperature which are set at 50, 65, and 80%, while the probability
intervals for tropical cyclone development are set at 20, 40, and 60%. 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.
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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.).
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Product Forecast Tools
The outlook maps are currently based on a number of forecast tools, many of which are objective and serve as an objective first guess. The final depiction is an
assessment of these objective forecast tools augmented by the forecaster when based on additional forecast information when appropriate to create the final product.
Forecast tools include MJO composites, empirical and dynamical based MJO, ERW and KW forecasts, and bias-corrected dynamical model guidance from a number of modeling systems.
Tropical cyclone areas are based on MJO composites and statistical and dynamical tropical cyclone forecast guidance products as well as raw model forecast guidance.
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Product Purpose
The product supports the NOAA mission in three primary ways:
- 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
- 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)
- Support various sectors of the U.S. economy (finance, energy, agriculture, water resource management) that have foreign interests.
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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.
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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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Product Resources
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Feedback and Questions
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www.nws.noaa.gov
