Disparate perspectives on observing and tracking the Madden-Julian Oscillation (MJO) over the past week result when comparing the RMM index and CPC velocity-potential based index. The RMM index indicates weakness in the MJO, as it generally has over the past 40 days, whereas the CPC index has tracked an enhanced subseasonal signal from the Maritime Continent into the Western Hemisphere over the course of January. The RMM index appears to be coming around to the CPC index, however, as dynamical model forecasts consistently show an emerging and strengthening intraseasonal signal in Phase 8/1 (corresponding to presence over the Western Hemisphere and Africa) over the course of Week-1. The Week-1 MJO signal is anticipated to be strong, with some moderation forecast for Week-2 as the signal shifts into the Western Indian Ocean. Whether the signal can propagate into the eastern Indian Ocean late in Week-2 is unclear, with dynamical model ensemble means showing a weakening signal in the RMM framework. This is to be taken cautiously, however, as differences in the phase speed of the intraseasonal envelope could well be cancelling out, causing the appearance of a weakening MJO due to the averaging. Expectations of the MJO in Phase 1 during Week-1 and Phase 2 in Week-2 are relied upon heavily in the present outlook. The low frequency footprint in the Pacific is currently being destructively interfered with by the subseasonal signal, but also influences the current outlook.
During the past week, Tropical Depression 1 (originally formed on 7 January) redeveloped near 10N/110W on 15 January. This disturbance tracked westward through the South China Sea and grazed the southern coast of Vietnam while gradually weakening, and has disspiated prior to this outlook. Dynamical models continue to suggest potential tropical cyclogenesis northeast of Madagascar during Week-1, but this signal has been persistent for several weeks in the GEFS and CFS and has yet to verify, which suggests these signals are a result of model bias. No tropical cyclone formation is anticipated during Week-1, with the Southern Hemisphere season off to a slow start in 2017. Dynamical models suggest potential for a system developing north of the Kimberly Coast of Australia and tracking westward during Week-2, resulting in a moderate risk of tropical cyclogenesis forecast here. Weak signals also exist for possible tropical cyclone formation during Week-2 in the South Pacific to the east of French Polynesia, but confidence is insufficient to forecast a specific hazard.
The Week-1 outlook attempts to mesh historical characteristics of MJO activity in Phase 1 with CFS and ECENS guidance. Phase 1 of the MJO features enhanced precipitation for the Southeast Pacific and South America, with high confidence of above-average rainfall forecast for these areas. An equatorial Rossby wave in the Atlantic also results in a high confidence of above-average rainfall there. An atmospheric river is expected to bring yet another surge of tropical moisture into western North America, with accompanying high confidence of above-average rainfall for California and parts of the Desert Southwest. A 500-hPa closed low over the Misssissippi Valley is expected to bring above-average rain to the Southeast U.S. with high confidence. Continued below-average rainfall for the Central Pacific is favored associated with the low frequency state. Remaining Week-1 precipitation shapes are a result of dynamical model consensus between the CFS and ECENS.
During Week-2, the outlook again utilizes CFS and ECENS guidance with a tilt towards MJO composites for Phase 2, and to a lesser extent, Phase 3. High confidence of above-average rainfall is expected from Southern India through the South China Sea and western Maritime Continent, associated with the presence of the active phase of the MJO. Moderate confidence of below-average rainfall east of New Guinea is also a typical MJO response to a signal in Phase 2 or 3. High confidence of below-average rains near the dateline in the Central Pacific continue from Week-1, associated with the low frequency footprint. Moderate confidence of above-average rains are also favored in Week-2 across the southern Maritime Continent and north of Australia associated with possible tropical cyclone formation. Remaining hazard areas are generally due to consistency among ensemble guidance, but lack a robust connection to the expected intraseasonal or low frequency states.
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.