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HOME > Climate & Weather Linkage > Global Tropics Benefits/Hazards

Last Updated - 03.21.17 (Routine)


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Global Tropics Hazards and Benefits Outlook Discussion

Last Updated: 03.21.17 Valid: 03.22.17 - 04.04.17
Madden-Julian Oscillation (MJO) activity remained obscured to incoherent over the past week, with the RMM index remaining at low amplitude throughout the period, while the CPC velocity potential-based index suggests the active MJO phase having a weak influence in the vicinity of the Maritime Continent or West Pacific. Most pronounced climate signals appear tied to a low frequency wavenumber-2 pattern with enhanced (suppressed) convection over the Maritime Continent and East Pacific (Indian Ocean and Central Pacific). The enhanced convection in the East Pacific, and the associated devastating heavy rains observed in portions of western South America, are tied to the large sea surface temperature (SST) anomalies observed in this region, with the latest weekly Nino 1+2 value registering +2.6 degrees C. The tripole of suppressed-active-suppressed convection spanning from the Indian Ocean through the Central Pacific has been lingering since last July, and is tied to prior climatic states of the negative phase of the Indian Ocean Dipole and the weak La Nina event observed during boreal autumn.

What little active MJO influence remains would destructively interfering with the low frequency state in the West Pacific during the forecast period, limiting any potential impacts. Dynamical models suggest an emerging active MJO signal over the Indian Ocean by Week-2, yet this is inconsistent with both the low frequency state and the most recent observed intraseasonal activity to the east of this region; therefore, this potential solution is heavily discounted. The low frequency state is expected to drive the tropical impacts during the upcoming two weeks, with extratropical influences murky due to the unique scenario of anomalously warm SSTs in the East Pacific that lack westward extension along the equator as would be anticipated based on previous warm El Nino-Southern Oscillation events. The anomalously warm SSTs in the East Pacific also appear predominantly surface driven, with little warm water available at depth, such that active convection may limit subsequent warming for the waters here due to the dependence on incoming shortwave radiation to build and maintain the observed anomalies.

No tropical cyclone activity was observed globally over the past week. The Joint Typhoon Warning Center currently gives a low chance of development prior to the forecast period for a low pressure system near 15S/117E. Both GEFS and ECENS guidance supports the system tracking south and undergoing tropical cyclogenesis before making landfall near the Pilbara Coast during Week-1, resulting in a high confidence of tropical cyclone formation. Elsewhere, tropical cyclogenesis is suggested within the monsoon trough to the south of Indonesia during Week-1 by ensemble guidance with moderate confidence, and an accompanying southeastward track towards Western Australia forecast. ECENS guidance suggests possible tropical cyclone formation to the northeast of Madagascar during Week-1, resulting in a moderate confidence of tropical cyclogenesis for this area. During Week-2 some GEFS members support possible tropical cyclogenesis in the South China Sea, with broad low-level troughing forecast in the ensemble mean, resulting in a moderate confidence of formation.

In the absence of a pronounced MJO signal, the current outlook is driven predominantly by the observed low frequency state with secondary influences from the aforementioned possible tropical cyclone activity and dynamical model consensus. During Week-1, above-normal rains are forecast in the East Pacific with high confidence for the area where recently observed SST values exceed the convective threshold of 27 degrees C and ensemble guidance supports this precipitation. Robust signals in dynamical model guidance are also forecast in the Coral Sea that are consistent with low frequency activity, resulting in a high confidence of much above-normal rains. A high confidence of below-normal rainfall is forecast in the Central Pacific near the antimeridan for both weeks, associated with continuing low frequency activity. High confidence of above-average precipitation is also forecast across the western U.S. during Week-1, tied with a surge of Pacific moisture anticipated to impact the region. Remaining areas highlighted during Week-1 have moderate confidence, and are consensus driven by dynamical model guidance.

The Week-2 outlook is once again driven heavily by the low frequency state anticipated to continue into this period. High confidence of above-normal rainfall in the vicinity of the Maritime Continent and East Pacific continue, with some uncertainty as to the coverage and extent of the rains for the East Pacific. Remaining portions of the tropics are highlighted for above-normal precipitation with moderate confidence in line with consistent ensemble guidance. Above-normal rains are possible in portions of the Great Plains with a mid-latitude cyclone potentially forming downstream of a 500-hPa trough.

Forecasts over Africa are made in consultation with the CPC international desk, and can represent local-scale conditions in addition to global-scale variability.

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:

  1. 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
  2. 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)
  3. 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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