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GTH Outlook Map and Data
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Last Updated -
07/29/25
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GTH Outlook Discussion
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Last Updated -
07/29/25
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Valid -
08/06/25 - 08/19/25
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Consistent with previous forecasts, the MJO remains coherent through late July. After regaining amplitude over the Maritime Continent earlier this month, RMM observations show the MJO signal maintaining its eastward propagation over the Western Pacific at a moderate amplitude during the past week, where it is poised to enter the Western Hemisphere (phase 8). This evolution aligns well with the upper-level velocity potential anomaly fields which show the enhanced convective envelope overspreading the equatorial Pacific, with more suppressed conditions developing over the Indian Ocean and Africa. Objective wave filtering of these fields also reveal a continuation of other modes of tropical variability, namely, a low frequency response centered over the Maritime Continent, though this latter feature appears to be weakening somewhat as of late.
Looking ahead, a continuation of subseasonal activity looks to be on tap, with some uncertainties surrounding its eventual strength later in August. RMM forecasts generally favor continued eastward propagation of the MJO over the Western Hemisphere and to the Indian Ocean during the next several weeks, but remain fairly low in amplitude. This weakening appears to be mainly due to destructive interference with the low frequency response, where the suppressed MJO phase may struggle to develop suppressed convection and overturn the persistent circulation anomalies over the Maritime Continent. Upper-level velocity potential forecasts from the GEFS and ECMWF reflect this weakening in anomaly space, but also maintain a wave-1 pattern consistent with organized MJO activity by mid-August. These forecasts also favor a slowing of the enhanced convective envelope over the Indian Ocean, which is likely tied to strong background easterlies aloft over the basin. Overall, guidance appears to well align with subseasonal forcing, with a large-scale flip in Tropical Cyclone (TC) genesis potential between both hemispheres, consisting of decreasing (increasing) chances for development in the western Pacific (eastern Pacific) basins heading into August. Additionally, any slowing of the MJO as it enters the Indian Ocean would also imply increasing chances for TC development in the tropical Atlantic towards the middle of August.
With MJO activity established over the equatorial Pacific, three TCs formed in the western Pacific and two TCs in the central Pacific during the past week. In the western Pacific, TC Francisco formed on 7/23 and tracked northwestward to the north of Taiwan, peaking at Tropical Storm intensity. Due to a complex steering ridge environment, this system meandered over the Taiwan Strait but succumbed to dry air and dissipated earlier this week. Father south, TC Co-May also formed on 7/23 to the east of the Philippines. This system quickly reached category 1 intensity and made landfall over northern Luzon late last week. After returning to sea while tracking to the northeast and weakening, Co-May took a sharp turn to the west under the aforementioned steering ridge environment where it restrengthened to Tropical Storm intensity. The latest official track from The Joint Typhoon Warning Center (JTWC) shows Co-May making landfall near Shanghai, China, and becoming a remnant low over the Jiangsu region of eastern China during the next few days. Father east, TC Krosa formed on 7/24 just to the east of Guam. This system has continued to track northward where the JTWC expects Krosa to turn to the west towards Honshu, Japan and maintain Tropical Storm strength later this week. The latest official track omits any landfall; however high winds and locally heavy heavy precipitation are possible for parts of Japan in week-1.
East of the Dateline in the Pacific, TC Iona formed on 7/27 near 145W/10N and has since strengthened to a Major Category 3 Hurricane. The National Hurricane Center (NHC) expects Iona to maintain a track due west, passing approximately 500 miles to the south of Hawaii and reach category 4 intensity during the next day or so, before gradually weakening later this week under a drier air environment. Directly behind TC Iona, TC Keli formed on 7/28 near 143W/11N and has strengthened to a Tropical Storm during the last 24 hours. The NHC expects Keli to maintain Tropical Storm Intensity while tracking westward over the next few days, but begin to weaken later this week due to increased shear and upper-level outflow from TC Iona in proximity. There are no immediate threats associated with these two systems for Hawaii, but the tropical situation bears monitoring in the coming days.
In the wake of TC Iona and TC Keli, the large-scale environment is expected to remain favorable for additional development in the eastern Pacific heading well into August. The NHC is monitoring 3 additional areas for potential TC development in the basin for week-1, one located to near 135W with 70% chances for formation during the next two days, and two areas located to the south of Mexico with 90% and 30% chances for formation during the next week. For this latter low risk area, probabilistic genesis tools indicate increasing chances for development, peaking early next week. Due to uncertainty in formation timing, 20% chances are posted in the outlook for week-2 near 120W-125W should any development be delayed. Behind this area, 40% chances are posted closer to 100W-105W where probabilistic tools and ensemble means show stronger signs for development, with formation much more likely within the week-2 period. For week-3, 20% chances are also posted to the south of Mexico where extended range tools maintain increased signals in the basin.
Across the Atlantic, there has been good consistency in the models pointing to increased genesis potential associated with a decaying frontal boundary over the southeastern U.S. and western Atlantic, as well as a tropical wave approaching the Bahamas early in week-2. To capture this potential, a broad area of 20% chances are posted with coverage extending into the eastern Gulf of America based on an increasing number of ECWMF solutions (dynamical and AI based) favoring a deepening low in the region. Farther east in the tropical Atlantic, there is also better support in the ECMWF based tools for additional tropical wave activity over the Main Development Region (MDR) later in week-2 and into week-3. However, the GEFS is less onboard with this realization, with Sahelian dust guidance also favoring elevated concentrations across the MDR through week-2 to inhibit formation potential. With the MJO favored to be located in the Indian Ocean by week-3, this would historically support a higher formation potential in the MDR, and 20% chances are posted over for week-3 where there is also better agreement in the extended range tools.
Following the uptick in western Pacific TC activity during July, the potential for additional TC activity looks to sharply decrease associated with the suppressed phase of the MJO bringing enhanced trades and increased shearing conditions into the basin. TC formation is still possible, mainly over the Philippine Sea, and 20% chances are posted for weeks 2 and 3 where the probabilistic tools show modest chances through the middle of August.
The precipitation outlook relies on an historical skill weighted blend of GEFS, ECMWF, and CFSv2 dynamical model ensemble guidance, anticipated TC tracks, with greater consideration of historical Western Hemisphere and Indian Ocean MJO composites for July-September. Tied to amplified 500-hPa ridging, above-normal temperatures with excessive heat conditions are possible over parts of eastern China and the southern tier of the CONUS. For hazardous weather concerns in your area during the next two weeks, please refer to your local NWS office, the Medium Range Hazards Forecast from the Weather Prediction Center (WPC), 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
