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ATTENTION:
The Climate Prediction Center is soliciting
comments from August 1, 2023 through December 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 -
05/14/24
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GTH Outlook Discussion
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Last Updated -
05/14/24
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Valid -
05/22/24 - 06/04/24
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Following a brief period of more coherent Madden-Julian Oscillation (MJO) activity during late April, the MJO has since weakened and became increasingly disorganized. The observed upper-level velocity potential anomaly fields depict a poor representation of the enhanced divergence envelope crossing the western Hemisphere, where there appears to be two other convective centers throughout the global tropics; one tied to a low frequency response in the western Indian Ocean, and another tied to Kelvin wave activity moving over the tropical Americas. The multiple centers of action have led to a much weakened signal in RMM space, as other modes of tropical variability have played a superseding role in driving convective and circulation anomalies during the past week or so.
Moving forward, however, there is growing support in the RMM forecasts for renewed MJO activity during the next week, with the enhanced phase propagating eastward from the Indian Ocean and crossing the Maritime Continent at a potentially moderate amplitude through the end of May. The amplifying MJO signal in RMM space over the Indian Ocean may, in part, be explained by constructive interference with the aforementioned modes of tropical variability in the basin, and consequently, there is still some question as to the potential coherence of the MJO with other modes of tropical variability favored to remain at play during the next several weeks. There is also uncertainty in regards to MJO phase speed, as upper-level velocity potential anomaly forecasts in the GEFS and ECMWF depict very different placements of the enhanced and suppressed convective envelopes by the end of the month. A slower, and more canonical phase speed favored in the GEFS may be in response to monsoonal circulations taking shape over Asia and Africa, though the Kelvin wave-like MJO phase speed featured in the ECMWF has been the predominant mode this spring. Despite these uncertainties, the large-scale circulation looks conducive for tropical cyclogenesis in the northern Indian Ocean and western Pacific later in May. Conversely, more unfavorable conditions for Tropical Cyclone (TC) development are anticipated over the tropical Americas following a potentially early start of the Hurricane season in the eastern Pacific during week-1.
No tropical cyclones formed during the past week. For week-1, the Joint Typhoon Warning Center (JTWC) is monitoring a tropical disturbance (92S) to the north of Madagascar. While formation chances are currently designated as low in the near-term, deterministic solutions have been fairly bullish for gradual development later this week. Any TC formation during this time of the year in the southwestern Indian Ocean would be very unusual, but is suggestive of the increasingly favorable conditions becoming established in the Indian Ocean. In the western Hemisphere, the National Hurricane Center (NHC) has yet to start issuing their regular Tropical Weather Outlooks (TWOs) with the start of the eastern Pacific Hurricane season beginning tomorrow (5/15). However, there is good continuity and support in the probabilistic TC genesis tools and raw ensembles for potential TC formation to the south of Mexico during mid to late week-1 before the suppressed phase of the MJO strengthens overhead.
For week-2, both the GEFS and ECMWF favor a band of strongly anomalous lower-level westerlies expanding eastward throughout the equatorial Indian Ocean tied to the renewed MJO. With anomalous easterlies favored to the north to induce a broad region of cyclonic flow, this results in elevated TC formation chances over the northern Indian Ocean during week-2. Based on climatology, and continued support in the probabilistic TC genesis tools, 60% chances for development are posted in the Bay of Bengal, with 20% chances in the Arabian Sea. Notably, strongly positive SST anomalies are observed throughout the entire basin, with some parts registering over 31 degrees C in the weekly mean which could provide plenty of fuel for any TCs that develop. These tools also show modest signals for additional development to the south of the equator between 70E and 80E, though given climatology for late May, there is not enough confidence to post a corresponding TC area for week-2. In the western Pacific, 20% chances for TC development are posted in the Philippine Sea in association with an equatorial Rossby wave forecast and support in the raw ensembles. Higher chances were considered, however odds for development are highest in the tools late in week-1, and any areas of low pressure may struggle to intensify with increased shear favored in the GEFS near the Marianas.
Should the MJO maintain coherence while propagating eastward across the Maritime Continent and possibly reach the Western Pacific during week-3, this would continue to favor additional TC development in the northern Indian Ocean and western Pacific based on historical MJO/TC composites. Therefore, 20% chances are posted across the Bay of Bengal and western Pacific which is consistent with signals in the probabilistic tools for week-3. These tools also point to reemerging signals in the eastern Pacific and Caribbean by the start of June. While TC genesis is certainly possible associated with transient equatorial Kelvin and/or Rossby waves that develop, no corresponding TC areas are posted in the outlook as TC formation would become more favorable later during the week-4 timeframe, even with the faster MJO propagation speed featured in the ECMWF.
The precipitation outlooks for weeks 2 and 3 are based on a historical skill weighted blend of the GEFS, CFS, ECCC, and ECMWF models, MJO composites and anticipated TC tracks. For temperatures, pre-monsoonal excessive heat, with maximum daytime temperatures possibly exceeding 110 deg F, is favored for many parts of the Sahel in Africa as well as portions of India and Pakistan. An amplifying subtropical ridge centered over the lower-latitudes of North America is also expected to increase the risk of excessive heat over the southern tier of the CONUS. 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 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
