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GTH Outlook Map and Data
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Last Updated -
12/23/25
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GTH Outlook Discussion
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Last Updated -
12/23/25
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Valid -
12/31/25 - 01/13/26
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Following a brief emergence of the Madden Julian Oscillation (MJO) index into the Western Hemisphere during the past week, the MJO has since returned to within the RMM unit circle. The GEFS depicts the MJO increasing in amplitude across the Indian Ocean (phases 2 and 3) during the next week. Conversely, the ECMWF and CFS are weaker, but show some evidence of an eastward propagating wave when applying objective filtering to the upper-level velocity potential. Despite more uncertainty in the near-term, there is better agreement in the longer range guidance, with the GEFS ensemble mean, as well as several individual ECMWF ensemble members depicting an increasing MJO signal over the Western Pacific (phases 6 and 7) during early to mid-January. Based on extended range lower-level zonal wind guidance, this evolution is also suggestive of the development of a low level westerly wind burst which could result in anomalously warm sea surface temperatures expanding across the Central Pacific helping to weaken La Nina.
The global tropics have been quiet during the past week, with the only tropical cyclone (TC) formation being TC Grant across the southeastern Indian Ocean on Dec 18. This system is forecast to continue moving west or west-southwest across the southern Indian Ocean. Aside from TC Grant, there are currently no other invests being monitored for additional TC development during week-1. By week-2, a favorable upper-level environment supports a 20-40 percent chance of TC formation over the southern Indian Ocean, especially if the MJO provides an additional convective boost. TC activity is also possible (20-40 percent chance) across the Gulf of Carpentaria eastward through the Coral Sea during week-2, mainly tied to climatology and support from enhanced probabilities in the ECMWF TC strike guidance. By week-3, the possibility of an MJO developing over the Western Pacific may further increase chances of TC development across the southwestern Pacific, and a 40-60 percent area was considered. However, there remains a good deal of uncertainty so only 20-40 percent chances are indicated at this time and can be reevaluated next week.
The precipitation outlook for weeks 2 and 3 is based on potential TC activity, La Nina, and informed by GEFS, CFS, Canadian, and ECMWF ensemble mean solutions. Some consideration is given to MJO composites over the Indian Ocean, although uncertainty in its evolution reduces its influence. Enhanced chances for below (above) normal rainfall are highlighted across the Indian Ocean north (south) of the Equator. Below normal rainfall is favored over the Equatorial Pacific consistent with La Nina, and also over much of northern Brazil. Anomalously warm temperatures are likely to accompany the dry conditions justifying an increased risk of above-average temperatures over northeastern Brazil where the hottest temperatures are predicted for week-2. Increased troughing across the Central Pacific and a potential Kona Low favors increased rainfall spreading across Hawaii from west to east during week-2 and likely persisting into week-3.
For hazardous weather conditions in your area during the coming two-week period, please refer to your local NWS office, the Medium Range Hazards Forecast produced by the Weather Prediction Center, and the CPC Week-2 Hazards Outlook. Forecasts made 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
