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Global Tropics Benefits/Hazards
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Last Updated - 01.15.19 (Routine)
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Global Tropics Hazards and Benefits Outlook Discussion |
| Last Updated: 01.15.19 |
Valid: 01.16.19 - 01.29.19 |
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In the past week, the Madden-Julian Oscillation interacted with Rossby waves and an emerging base state as it crossed the central and eastern Pacific, leading to weakening. The RMM index reflects this deamplification, bringing the signal back inside the unit circle, but has continued eastward propagation over the past few days. Dynamical model guidance is in good agreement that the MJO signal is likely to re-emerge over the Indian Ocean and Maritime Continent (between phases 3 and 4) early in Week-1. The amplitude of this signal is likely to remain modest, maintaining a value of about 1 on the RMM index, and will continue eastward propagation through Week-2. The convective envelope is expected to reach phase 5 at the end of Week-1 and continue through to phase 7, toward the western Pacific, for Week-2. Toward the end of Week-2, model guidance consistently indicates a possible stalling and weakening in the signal; however, the convective envelope could constructively interact with the emerging El Nino base state, so the confidence in this forecast of weakening toward the end of Week-2 is low. A recent westerly windburst in the western Pacific is likely to trigger a response along the equatorial Pacific, possibly causing a downwelling Kelvin wave, which could deepen the thermocline in the central and eastern Pacific. This would lead to increased availability of warm water for these regions, aiding the developing El Nino.
The Indian Ocean and western Pacific basins have been fairly active through the past month with the active MJO and abundant Rossby wave activity. For Week-1, areas of likely cyclogenesis have been highlighted for both these regions. In the southern Indian Ocean, there is high confidence in a formation south of Java. Model guidance shows good agreement and continuity in this forecast, with the TC likely tracking west toward the central Indian Ocean. The MJO convective envelope is also expected to be exiting the Indian Ocean and shifting over the Maritime Continent during Week-1, which usually leads to an active TC period. Another region forecast for a TC formation is centered near 140 E in the western Pacific. This is another system that has consistently formed in model guidance through the past several runs, so with the agreement in the dynamical models, confidence for this forecast is high. This TC is likely to track westward toward the Philippines. With the MJO forecasted to shift further east over the Pacific in Week-2 and possible weaken, these basins are expected to remain quiet in Week-2 at this time.
Forecast precipitation patterns for Week-1 are linked to either TC activity or larger dynamical model patterns, with some MJO influences. There is high confidence that a large region stretching from the central Indian Ocean to the Maritime Continent is expected to receive above normal precipitation. Over the western Pacific, two other areas of above normal precipitation are expected for Week-1, supported by both the expected TC activity and the MJO signal as it shifts further over the Maritime Continent. Model guidance is in good agreement over a region of dryness for northeastern Australia and the south Pacific, which is consistent with MJO composites for phases 3 and 4. With the increased warm water availability over the eastern Pacific and support from dynamical guidance, a region of above normal precipitation has been forecast just north of the equatorial eastern Pacific with moderate confidence. The dry signal over Brazil is expected to continue through Week-1. For the U.S., anomalously cold temperatures are likely for the western and central Gulf Coast due to the large-scale upper-level pattern, coinciding with the lagged impacts of the MJO signal passing through the western hemisphere last week into this week; for more information on this particular forecast, please see the U.S. Hazards Outlook.
For Week-2, the forecast is consistent with the typical impacts seen from a MJO signal in phases 5-7. The suppressed convective envelope is forecast over the Indian Ocean and parts of the Maritime Continent, causing below normal precipitation for these two regions. There is more confidence in this forecast over the Indian Ocean, due to the variability in the speed of the eastward propagation in the models. For the western Pacific and the SPCZ, above normal precipitation is expected, which is supported by both dynamical model guidance and MJO phase 5/6/7 composites. The region of above normal precipitation over the eastern Pacific is expected to continue into Week-2.
Forecasts over Africa and South America are made both in consultation with the CPC international desk and using dynamical model consensus, and therefore can represent local scale conditions in addition to global scale variability.
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Product Release Information
The full Global Tropics Hazards and Benefits 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 webinar) open to all interested parties in which the latest conditions in the Tropics and the just released outlook and associated impacts are discussed. There is an opportunity to ask questions after the briefing and the briefings are available at the Live Briefing Archive and soon will be recorded.
CPC also issues an operational update of this product every Friday by 1730 UTC to further support the NWS regions. The update only spans the release period from June 1 through November 30 and a region from 120E to the Prime Meridian in longitude and from the equator to 40N in latitude. The update does not extend the time horizon of the product, but rather applies for the remaining 4 days of the previous Week-1 time period and Days 5-11 from the previous Week-2 period. This page will depict both the original and updated outlook maps as well short text outlining the forecast rationale for any changes.
Product Description
The Global Tropics Hazards and Benefits Outlook is a forecast for areas with elevated odds for above- or below-median rainfall, above- or below-normal temperatures and regions where tropical cyclogenesis is favored for the upcoming Week-1 and Week-2 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 yellow respectively. Above(below) normal temperature forecast areas are depicted in orange and below respectively. Favored areas for tropical development are shown in red. Two measures of confidence are indicated, high (solid) and moderate (hatched) and are currently subjective in nature and not based on an objective system. Work towards a probabilistic format of the product and so an objective measure of confidence is ongoing. 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.
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.).
Product Forecast Tools
The outlook maps are currently created subjectively based on a number of forecast tools, many of which are objective. The final depiction is an assessment of these forecast tools based on a number of factors to create the final product. Work is ongoing to create an objective consolidation of some of the available forecast tools to serve as a first guess for the forecaster. Forecast tools include MJO composites, empirical and dynamical based MJO, ERW and KW forecasts, and raw dynamical model guidance from a number of modeling systems. Tropical cyclone areas are based on MJO composites and statistical and dynamical tropical cyclone forecasts as well as raw model forecast guidance.
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.
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.
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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