Latest Tropical Information from The United States Navy COMSECPAC and AOCC
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MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 7.4N 144.2E TO 8.4N 140.6E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 15 TO 20 KNOTS. METSAT
IMAGERY AT 020600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 7.4N 144.0E. THE SYSTEM IS MOVING WESTWARD AT 10 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 6.7N
145.5E, IS NOW LOCATED NEAR 7.4N 144.1E, APPROXIMATELY 360 NM SOUTH
OF GUAM. RECENT ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS DEEP
CONVECTION DEVELOPING ALONG THE WESTERN PERIPHERY OF A LOW LEVEL
CIRCULATION CENTER (LLCC) ALSO EVIDENT IN RECENT MICROWAVE SATELLITE
IMAGERY INCLUDING A 020414Z AMSU PASS. THIS DISTURBANCE LIES
EQUATORWARD OF AN UPPER-LEVEL RIDGE AXIS, IN AN AREA OF LOW TO
MODERATE EASTERLY VERTICAL WIND SHEAR, INCREASING OUTFLOW ALOFT,
AND FAVORABLE SEA SURFACE TEMPERATURES. DYNAMIC MODEL GUIDANCE
INDICATES TROPICAL CYCLONE FORMATION WITHIN THE NEXT DAY OR TWO.
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. BASED
ON LOW-LEVEL CONSOLIDATION, IMPROVING CONVECTIVE SIGNATURE, AND
FAVORABLE ENVIRONMENTAL SUPPORT, THE POTENTIAL FOR THE DEVELOPMENT
OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY
030830Z.//
NNNN
The RMM-based MJO index indicates a weak signal during the past week, while the CPC velocity potential based index indicates little coherent signal, as well. The pattern of convection continues to be largely dominated by the high-amplitude low-frequency state, though robust atmospheric Kelvin Wave activity is also contributing. This is most evident over parts of the Maritime Continent where enhanced convection is currently observed, which is at odds with the ongoing ENSO state.
Dynamical model outputs generally indicate a weak MJO signal during the next two weeks, although the GEFS forecast has a very weak signal over the Western Hemisphere during Week-2. This could be a reflection of the evolution of the background state, or due to continuing Kelvin Wave activity. In either case, the MJO is not expected to contribute to any significant portion of tropical convective variability. Statistical tools indicate little coherent MJO signal as well. Therefore, the forecast is based on the ENSO state and dynamical guidance from the CFS and ECMWF coupled systems.
No tropical cyclones developed during the past week. During the next 7 days, tropical cyclone formation odds are enhanced near the Kimberley Coast of Australia. There is a low chance of a weak tropical cyclone forming near Madagascar during the next several days, though the probability is too low to warrant a map depiction. During Week-2, the only region that can be delineated on the map is a fairly large region in the Northwest Pacific, where overall conditions seem somewhat favorable. Over the Indian Ocean near Sri Lanka, there is a low risk of formation associated with a forecast area of enhanced convection. The latest 06Z run of the GEFS indicates about a 10 to 15 percent chance of formation over the eastern Pacific basin, and the coupled CFS system suggests the first system in that basin could form as early as Week-3. This will continue to be monitored closely.
During Week-1, convection is likely to be enhanced over much of the Pacific cold tongue extending to near the Date Line due to the ENSO state. This convection could bring heavy rains all the way to the South American coast. Suppressed convection is more likely over parts of Southeast Asia from the Bay of Bengal to the South China Sea, as well as parts of the Maritime Continent. In spite of the robust low-frequency state, confidence is lower here due to the enhanced phase of a Kelvin wave impacting this region early in the period. Dry conditions are favored over northeast South America and parts of the Caribbean Sea, with above-average rainfall favored farther south over parts of South America.
For Week-2, convection is forecast to be above average from west of the Date Line all the way to the South American coast. Both the CFS and ECMWF are in agreement on this point. In the wake of the enhanced Kelvin wave convection over the Maritime Continent early in Week-1, suppressed rainfall is highly likely over most of the Maritime Continent and Southeast Asia. Models are in good agreement indicating enhanced rainfall over the Gulf of Mexico and adjacent coastal regions. The low-frequency state is expected to continue to favor the pattern indicated over South America, namely, suppressed rainfall across the northern part of the continent and enhanced rainfall to the south.
Depicted areas of enhanced or suppressed rainfall over Africa are produced in collaboration with CPCs Africa Desk.
Product Release Information
The Global Tropics Hazards and Benefits Outlook is released once per week every Tuesday at 1530 UTC (1630 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.
Product Description
The Global Tropics Hazards and Benefits Outlook is a forecast for areas with elevated odds for above- or below-median rainfall and regions where tropical cyclogenesis is favorable or unfavorable 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. 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 forecastersProvide 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.
Appendix
1. Rainfall hazard areas:
Additional details for the rainfall verification procedure are given here. Outgoing Longwave Radiation (OLR) data are used since OLR is a generally good proxy for rainfall in the Tropics and also since there is a reliable, consistent and lengthy base period record in which to determine anomalies. The OLR data is 1x1 and weekly averages are calculated at each grid point for all julian days over the 30 year period of record. OLR value limits are then determined for a number of percentiles, including tercile cutoffs of 33% and 66%. The realtime weekly mean OLR data is then categoried into one of three categories above-, near- or below-average weekly mean OLR at each grid point. Weekly mean values below or equal to the 33% cutoff would verify as wet and those greater than or equal to the 66% cutoff would verify as dry. Only grid points in which a forecast was made (i.e. a green or yellow area designated in the outlook) are verified. As an example, forecasts that indicated yellow on the outlook map would be credited with a "hit" if the corresponding observations also ranked in the upper third of the historical distribution, while those grid points that ranked in the middle or lower part of the distribution were credited as a "miss". Vice versa for green forecasted areas.
The Heidke skill score (HSS) is a hit-based skill score and is calculated through the following relationship that compares the number of correct and incorrect hits along with the number of expected hits from random chance:
HSS (%) = 100 * (H - E) / (T - E)
where H = Number of correct forecasts, E = Expected number of correct forecasts (1/3 of total), and T = total number of forecasts.
The HSS is a measure of how well a forecast did relative to a randomly selected forecast. A score of 0 means that the forecast did no better than what would be expected by chance. A score of 100 depicts a "perfect" forecast and a score of -50 depicts the "worst possible" forecast. The second set of time series plots are obtained by simply multiplying the forecast coverage by the above skill score value which weights more heavily outlooks with greater forecast coverage.
2. Tropical cyclone hazard areas:
Using the 2x2 contingency table below, the "Hit Rate" is the proportion of correct "yes" and correct "no" forecasts: (a+d)/n. The "Success Ratio" is the proportion of correct "yes" forecasts: a/(a+b). The "Critcal Success Index" or threat score is a/(a+b+c). The Probability of Detection (POD) and False Alarm Rate (FAR) are calculated by a/(a+c) and b/(a+b) respectively. The total number of forecasts, n, is given by n=(a+b+c+d).
The HSS for the tropical cyclone outlooks is calculated based on the 2x2 contingency table with the following formula:
HSS = 2*(ad-bc) / [(a+c)(c+d) + (a+b)(b+d)]
ENSO weekly update:
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdfMJO weekly update:
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdfEarth System Research Laboratory
http://www.cdc.noaa.govNational Hurricane Center:
http://www.nhc.noaa.gov/Central Pacific Hurricane Center:
http://www.prh.noaa.gov/hnl/cphc/Joint Typhoon Warning Center:
http://www.usno.navy.mil/JTWCCPC African Desk:
http://www.cpc.ncep.noaa.gov/products/african_desk/USAID/FEWS:
http://www.cpc.ncep.noaa.gov/products/fews/Australian Government Bureau of Meteorology:
http://www.bom.gov.au/climate/
http://www.bom.gov.au/weather/nt/
Educational Material
Atmospheric blocking is commonly referred to as the situation when the normal zonal flow is interrupted by strong and persistent meridional flow. The normal eastward progression of synoptic disturbances is obstructed leading to episodes of prolonged extreme weather conditions. On intraseasonal time scales the persistent weather extremes can last from several days up to a few weeks, often accompanied by significant temperature and precipitation anomalies. Examples of the 500 hPa height and anomaly fields associated with mature blocking episodes over thenortheastern Atlantic and the North Pacific. These two regions are preferred areas for atmospheric blocking during the northern hemisphere cold season.
A common finding among scientific studies is that these long-lived weather extremes are associated with recurrent atmospheric flow anomalies. Numerous studies have found that the poor forecast skill beyond a few days results principally from the inability of numerical weather prediction models to simulate the onset and evolution of blocking flows.
Definition of Blocking Index Definition
Publications
Carrera, M. L., R. W. Higgins, and V. E. Kousky, 2004: Downstream weather impacts associated with atmospheric blocking over the Northeast Pacific. J. Climate, in press.
Chen, W. Y., and H. M. Van den Dool, 1995: Low-frequency anomalies in the NMC MRF model and reality. J. Climate, 8, 1369-1385.
Chen, W. Y., and H. M. Van den Dool, 1997: Asymmetric impact of tropical SST anomalies on atmospheric internal variability over the North Pacific. J. Atmos. Sci., 54, 725-740.
Chen, W. Y., and H. M. Van den Dool, 1999: Significant change of extratropical natural variability and potential predictability associated with the El Nino/Southern Oscillation Tellus, 51A, 790-802..
Higgins, R. W., and S. D. Schubert, 1994: Simulated life cycles of persistent anticyclonic anomalies over the North Pacific: Role of synoptic-scale eddies. J. Atmos. Sci., 51, 3238-3260.
Higgins, R. W., and S. D. Schubert, 1996: Simulations of persistent North Pacific circulation anomalies and interhemispheric teleconnections. J. Atmos. Sci., 53, 188-207.
Higgins, R. W., and K. C. Mo, 1997: Persistent North Pacific circulation anomalies and the tropical intraseasonal oscillation. J. Climate, 10, 223-244.
https://docs.google.com/file/d/0B-QqrlanmaMBWGxCal9fUTFXQ3M/edit?usp=docslist_api
https://docs.google.com/file/d/0B-QqrlanmaMBcHQzS1pBdE1IV28/edit?usp=docslist_api
