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ATTENTION:
The Climate Prediction Center is soliciting
comments from August 1, 2023 through January 31, 2024 on the implementation
of the Week 2
and experimental Week 3 Global Tropics Hazards Outlook.
Here is the Survey.
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GTH Outlook Map and Data
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Last Updated -
09/26/23
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GTH Outlook Discussion
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Last Updated -
09/26/23
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Valid -
10/04/23 - 10/17/23
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The RMM-based Madden Julian Oscillation (MJO) index has returned to the unit circle during the past week, with dynamical model forecasts being largely incoherent regarding any significant amplification or eastward propagation of the intraseasonal signal. However, the upper-level velocity potential field indicates a more organized wave-1 asymmetry structure in its spatial pattern. Enhanced upper-level divergence is noted across the Indian Ocean, Asia, and the Western Pacific, and enhanced upper-level convergence is depicted across the Eastern Pacific, Americas, and the Atlantic. Both the GEFS and ECMWF ensembles show an eastward expansion of the enhanced convective envelope into the Eastern Pacific and Western Atlantic by weeks 2 and 3 consistent with an MJO propagation, while the low frequency enhanced convective signal remains across the Central Pacific. Suppressed convection is forecast over the Indian Ocean, with some possible expansion into the Western Pacific by week-3.
The Atlantic basin has been active over the past week with two tropical cyclone (TC) formations. Tropical storm Ophelia developed on 9/22 and impacted the eastern U.S. Tropical Storm Phillipe formed on 9/23 over the Main Development Region (MDR), with the National Hurricane Center indicating a high chance of an additional TC forming over this area during the next week. In contrast, the Eastern Pacific has been quiet despite the ongoing El Nino, with no new TC formations since Tropical Storm Kenneth on 9/19. The Western Pacific has also been generally quiet, with only Tropical Depression 13W developing on 9/24 over the South China Sea and tracking west into Vietnam and remaining weak.
Given the favorable upper-level conditions forecast during the next week, a ramp-up in TC activity is predicted across the Western Pacific, with the Joint Typhoon Warning Center monitoring several areas of disturbed weather for potential development. This is forecast to persist into week-2, with today’s Global Tropics Hazards Outlook highlighting a 40 percent chance of TC development during week-2 across the Western Pacific and South China Sea and a 20 percent chance of TC development over the Bay of Bengal. By week-3, more suppressed convection may begin to build over the Western Pacific, leading to diminishing TC formation probabilities, although a 20 percent chance of TC development remains indicated for the period. Today’s guidance is fairly robust with increasing activity over the Eastern Pacific during weeks 2 and 3 as the main convective envelope expands eastward and is also consistent with the El Nino climatology. A 40 percent chance of TC development is indicated across the basin for week-2, with a 20 percent chance during week-3. The 20 percent chance regions also extend into the western Caribbean during weeks 2 and 3 consistent with the increasing climatology in this area during October.
Across the rest of the Atlantic, the MDR is forecast to quiet down by week-2, although additional TC development cannot be ruled out given the anomalously warm sea surface temperatures and the convective envelope moving overhead by mid-October. However, TC climatology begins to wane this time of year, and the dynamical models are not particularly robust in depicting any formations, so no TC formation areas are depicted in the MDR during weeks 2 and 3. Closer to the U.S. East Coast, both the GEFS and ECMWF ensembles depict surface low pressure underneath the surface high over the Northeast during week-2, similar to Tropical Storm Ophelia. Given the persistence of this pattern, and the elevated potential for such a system to acquire tropical or subtropical characteristics along the Gulf Stream, a 20 percent chance for TC formation is depicted along the southeastern coast of the U.S. for week-2.
Forecasts for enhanced and suppressed rainfall based on a historical skill weighted blend of GEFS, ECMWF, CFS and Canadian ensemble forecasts, and seasonal composites of El Nino, as well as composites of MJO events from the Western and Eastern Pacific for weeks 2 and 3, respectively. For hazardous weather concerns in your area of 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 (WPC), 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
