The Madden Julian Oscillation (MJO) and a couple of equatorial Rossby (ER) waves are the main drivers of the large-scale tropical flow over the Indian Ocean and Maritime Continent during this forecast period. The MJO forecast is especially complicated this week because the RMM phase space does not capture the current state of the MJO very well. In an RMM sense, the MJO is in phase 3 with an amplitude of about 1 and is forecast to weaken substantially over the next few days. Some dynamical model guidance then suggests that the RMM amplitude will strengthen when the MJO is over the Maritime Continent towards the end of the month. However, the MJO's footprints in the OLR and wind anomaly fields over the Indian Ocean are stronger than the RMM index suggests. Dynamical guidance also propagates the MJO convective field eastward, roughly maintaining its current strength over the need couple of weeks. Additionally, an ER wave that is currently over the Indian Ocean is forecast to propagate westward and weaken during the Week-1 period. Another ER wave, which is presently just east of the Maritime Continent, is forecast to propagate westward and be over the western Indian Ocean by the end of the Week-2 period.
During Week-1 we have moderate confidence that the superposition of anomalous convection associated with the MJO and the ER wave over the Indian Ocean will provide a favorable environment for tropical cyclone formation just east of Madagascar. Another region of anomalous precipitation is also likely, centered around 80E about 20 degrees south of the Equator. Enhanced convection along the coast of northern Australia is likely to bring above-average rainfall to the region as well as a high probability of tropical cyclone development. Slightly further east, enhanced convection associated with the ER wave over the central Pacific is forecast to bring above-average rainfall to Hawaii and points southwest of the islands.
Also during Week-1, Tropical Cyclone Linda, currently between the northeast coast of Australia and New Caledonia, is forecast to track southeast, leading to a high chance for above-average rainfall in its wake. Lastly, a broad region of high pressure is expected to bring above-average temperatures to much of Libya during Week-1.
MJO and ER wave activity also dominate the Week-2 forecast with moderate chances of above-average rainfall over, south, and west of Hawaii. The twin gyres associated with the ER wave over the central Pacific are expected to propagate further west and are associated with moderate chances of anomalous rainfall. Additionally, gyres associated with ER waves often provide conducive environments for the formation of tropical cyclones, so there are moderate risk areas for TC formation around each gyre. Convection over the northern coast of Australia is expected to continue during Week-2 and the anomalously warm temperatures over northern Africa are expected to continue expanding eastward over Egypt and the Arabian Peninsula.
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.
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.
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.
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.