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GTH Outlook Map and Data
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Last Updated -
03/18/25
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GTH Outlook Discussion
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Last Updated -
03/18/25
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Valid -
03/26/25 - 04/08/25
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Since entering the Indian Ocean at a slowed phase speed earlier in month, RMM observations show a more canonical eastward propagation of the MJO signal, though its amplitude has gradually weakened during the past few days in phase 3. Objective filtering of upper-level velocity potential and OLR anomaly observations offer a slightly different perspective, which shows the core of the MJO enhanced envelope closer to 110E, where according to composites during Feb-Apr, is more reflective of a phase 4 MJO expression at present. During the next week, RMM forecasts favor a very fast phase speed over the Maritime Continent, while maintaining a low to near zero amplitude as it enters the Western Pacific. Such a phase speed is uncharacteristic of the MJO, and the thinking is that this behavior is related to the rapid development of suppressed divergence aloft favored in the western Indian Ocean tied to exiting equatorial Kelvin wave activity in the region. This would cause the RMM index to “catch-up” to the enhanced convective MJO envelope that actually lies closer to the Western Pacific, consistent with the latest OLR and velocity potential short-term forecast fields.
Beyond week-1 however, dynamical models remain at odds with the strength and evolution of the MJO once in the Western Pacific. The ECMWF continues to devolve the upper-level velocity potential fields into a multiple wave pattern by weeks 2 and 3, suggesting other modes of variability, namely, an emerging low frequency signal in the eastern Pacific characteristic of El Nino conditions, are playing a growing role in the global tropics. The GEFS and CFS have been less supportive of this feature, likely owing to the shallowness of the anomalously warm water in eastern Pacific, and favor a more organized MJO over the western Pacific. However, these models also struggle to maintain its eastward propagation and its potential to break through the low-frequency enhanced trade wind regime along Date Line heading into April. Given the unusual structure of the base state, and its potential interactions with the evolving subseasonal activity, there is a higher degree of uncertainty in the updated outlook. Despite these uncertainties, there continues to be decent support in the model guidance for additional tropical cyclone (TC) development in the southern Indian Ocean and South Pacific later in March. Conversely, decreased chances for TC development are favored over the southeastern and south-central Indian Ocean following a pretty active period from late February into early March.
No TCs formed during the past week, with no active TCs at present. The Joint Typhoon Warning Center (JTWC) is monitoring a disturbance (91S) in the southeastern Indian Ocean with increased chances of formation during week-1. With the GEFS and ECMWF both favoring the persistence of strong anomalous lower level westerlies over this part of the basin and extending eastward by week-2, conditions look to remain favorable for additional development off the Kimberley Coast eastward to the Coral Sea. Therefore, 40% chances are posted from approximately 120E to 145E to the north of Australia, with a broader area of 20% chances, consistent with the week-3 GTH outlook issued last week. Probabilistic genesis tools also feature increased signals north of the equator in the Philippine Sea; however, the environment may not be yet conducive for genesis, precluding any TC shapes at this time. TC development is also possible to the northeast of Madagascar based on these tools, but forecast confidence is too low especially if the suppressed phase of the MJO should prevail over this part of the basin. Given the aforementioned differences in the model guidance with respect to the MJO, the week-3 perspective is unclear, which is compounded by a quieter genesis climatology entering April. However, 20% chances are posted to the north of Australia and extending eastward into the South Pacific where models favor the persistence of anomalous lower-level westerlies with modest signals in the probabilistic tools.
Forecasts for enhanced and suppressed precipitation are based on a historical skill weighted blend of CFSv2, GEFS, and ECMWF ensemble systems, with some consideration of MJO and ENSO composites for Feb-Apr due the uncertainties associated with predicted subseasonal activity, as well as the non-canonical low frequency base state. The model blend does well reflect the suppressed precipitation near the Date Line tied to the enhanced trades, with warming SSTs supporting an expanded coverage of enhanced precipitation over the eastern and central equatorial Pacific, where the highest probabilities are issued. Above-normal temperatures are favored over much of the western CONUS and many parts of eastern South America, where drought related conditions are being registered. In addition, excessive heat conditions are possible in portions of western Africa and the Indian subcontinent where daytime temperatures could exceed 105 degrees F. Precipitation forecasts over Africa are made in coordination with the International Desk at CPC. For hazardous weather concerns in your area in the U.S. during the next two weeks, 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.
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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
