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GTH Outlook Map and Data
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Last Updated -
10/01/24
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GTH Outlook Discussion
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Last Updated -
10/01/24
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Valid -
10/09/24 - 10/22/24
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The MJO is currently active and situated across the Western Hemisphere leading to an uptick in tropical cyclone (TC) activity across the North Atlantic. By week-2, dynamical models depict an eastward propagation of the MJO into the Indian Ocean and Maritime Continent and the suppressed phase moving over the Americas. This favors a reduction in TC development chances across the Atlantic and East Pacific, although a Convectively-Coupled Kelvin Wave (CCKW) may destructively interfere with the suppressed MJO phase leading to an enhancement of TC development chances over the Caribbean later in October. The highest chances for TC formation are forecast over the Western Pacific tied to the incoming MJO combined with an enhanced low frequency convective signal likely related to the emerging La Nina.
While formation occurred in the prior week, category-4 Hurricane Helene made landfall on the Florida Big Bend region on 9/26, with extensive damage and catastrophic flooding extending through the Southeast and Carolinas. Hurricane Issac formed on 9/26 over the North Atlantic and Tropical Storm Joyce (9/27) was a weak, short-lived system across the Main Development Region (MDR). Tropical Storm Kirk developed on 9/29 and is forecast to become a powerful hurricane over the open waters of the Atlantic. The easterly wave behind Kirk is strongly favored to develop into a TC during week-1. The National Hurricane Center (NHC) continues to monitor a tropical disturbance over the northwestern Caribbean that may develop into a tropical cyclone during week-1. However, recent model runs have slowed down potential development, carrying elevated chances into the week-2 period. Of particular concern is this new system could bring heavy rainfall to parts of the Gulf Coast and some of the same regions impacted by Helene. Given some emerging timing uncertainty, a 20-40% chance of TC development is indicated during week-2 over this area. While TC development in the MDR is favored to slow down due to the October climatology along with a more suppressed convective environment aloft, it is plausible to get an additional easterly wave to spin up into a TC given how active it has been recently, favoring 20-40% chances for TC development in week-2 over the MDR. By week-3, TC development is most favored in the Caribbean where a 20-40% chance is highlighted, consistent with climatology and the aforementioned CCKW.
Across the Eastern Pacific, Hurricane John regenerated off the southern coast of Mexico on 9/25 causing prolonged impacts across the region. Two additional areas are being monitored for development by NHC with high chances during week-1. By week-2, the suppressed phase of the MJO favors a reduction in TC activity. The Western Pacific has been active as well with the formations of Cimaron (9/25), Jebi (9/27), and Krathon (9/28). Cimaron was a weak tropical storm that meandered to the south of Japan. Jebi briefly attained typhoon status before weakening as it skirted Japan. Krathon is the most significant of these systems to have formed, becoming a super typhoon and resulting in flooding across parts of the Philippines and is now forecast to move toward Taiwan. The large scale environment is likely to remain favorable for TC development through much of October, due to the upstream MJO combined with the low frequency enhanced convective footprint providing an additional boost. As a result, 40-60% chances of TC development are forecast for weeks 2 and 3 across the Western Pacific east of the Philippines, with a 20-40% chance extending into the South China Sea.
As the MJO moves into the Indian Ocean by week-2, TC development is possible in the Bay of Bengal and Arabian Sea (20-40% chance for both weeks 2 and 3). This is supported by increased filtered TC track densities in the GEFS and ECENS models. An early start to the South Indian Ocean season is also possible, with Invest 91S being monitored for possible development near 10 deg S, 75 deg W. Any development is most likely to occur during week-1, with decreasing chances by week-2 precluding a related TC formation area in the forecast.
Forecasts for above- and below-normal precipitation are based on composites of MJO activity in the Indian Ocean and Maritime Continent combined with the low frequency enhanced convection over the region. The suppressed phase of the MJO favors increased chances for below-normal precipitation across the Eastern Pacific and extending into parts of the Americas. Above-normal temperatures are forecast across the western half of the contiguous U.S. during week-2. 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
[email protected], [email protected], [email protected] and [email protected] 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
