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Tropical Depression Thirteen Forecast Discussion Number 2

2017-09-06 04:38:38| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Tue Sep 05 2017 000 WTNT43 KNHC 060238 TCDAT3 Tropical Depression Thirteen Discussion Number 2 NWS National Hurricane Center Miami FL AL132017 1000 PM CDT Tue Sep 05 2017 Convection continues near the center of the depression, although it isn't very curved at this time. Overall, westerly shear is keeping most of the thunderstorm activity in the eastern semicircle of the cyclone. Dvorak estimates are unchanged, so the initial wind speed remains 30 kt. Global models suggest that the westerly shear should gradually subside over the next few days while the depression moves over very warm water. This is a recipe for strengthening, and the official forecast is similar to the previous advisory. More guidance members are showing the cyclone eventually becoming a hurricane than the last cycle, so the peak intensity is bumped up 5 kt, staying a bit above the model consensus. Microwave data indicate the depression continues to drift eastward. The cyclone should gradually turn southward and southwestward as high pressure builds near Texas, along with an increase in forward speed forecast on Friday. The guidance has come into somewhat better agreement on the track forecast during the past 6 hours, and little change was made to the previous advisory. The NHC forecast remains on the southern side of the guidance, since models in that part of the southwestern Gulf of Mexico tend to have a northward bias. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 22.2N 96.4W 30 KT 35 MPH 12H 06/1200Z 22.1N 96.0W 35 KT 40 MPH 24H 07/0000Z 21.8N 95.5W 45 KT 50 MPH 36H 07/1200Z 21.5N 95.2W 50 KT 60 MPH 48H 08/0000Z 21.2N 95.3W 55 KT 65 MPH 72H 09/0000Z 20.8N 95.9W 60 KT 70 MPH 96H 10/0000Z 19.4N 98.1W 20 KT 25 MPH...POST-TROP/INLAND 120H 11/0000Z...DISSIPATED $$ Forecaster Blake

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Hurricane Irma Forecast Discussion Number 28

2017-09-06 04:36:40| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 05 2017 000 WTNT41 KNHC 060236 TCDAT1 Hurricane Irma Discussion Number 28 NWS National Hurricane Center Miami FL AL112017 1100 PM AST Tue Sep 05 2017 The satellite view of Irma remains quite spectacular, with an extremely well-defined eye and a large, symmetrical CDO. Reports from NOAA and Air Force Hurricane Hunter aircraft indicate that the central pressure had fallen at about 1 mb per hour since this morning, although very recently the deepening trend has leveled off. Based on SFMR-observed winds from the aircraft, the current intensity remains at 160 kt. The Meteo-France radar imagery suggests a concentric eyewall structure and observations from the aircraft hinted at a secondary wind maximum. If an eyewall replacement becomes more definitive, this would likely halt additional strengthening, and could even lead to some weakening. The official intensity forecast is near or above the model consensus. Given the favorable atmospheric and oceanic environment, Irma is likely to remain a Category 4 or 5 hurricane for the next few days. Latest center fixes from satellite imagery and the aircraft indicate that Irma is now moving west-northwestward, or 285/13 kt. A strong ridge extending southwestward from the central Atlantic is expected to steer Irma west-northwestward during the next couple of days. A large mid-latitude trough over the eastern United States is forecast to lift northeastward, allowing the ridge to build westward and keep Irma on a westward to west-northwestward heading through Friday. In 4 to 5 days, a small trough diving southward over the east-central U.S. is expected to weaken the western portion of the ridge, causing Irma to turn poleward. Some of the dynamical models have shifted northward a bit from the previous cycle, with the normally reliable GFS looking like a northeast outlier. The official track forecast leans toward the ECMWF solution. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively. KEY MESSAGES: 1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northern Leeward Islands, including the Virgin Islands and Puerto Rico, on Wednesday. Preparations should be rushed to completion. 2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, with hurricane watches for Haiti, the southeastern Bahamas and the Turks and Caicos. Irma is likely to bring dangerous wind, storm surge, and rainfall to these areas from Wednesday night through Friday. 3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 17.4N 61.1W 160 KT 185 MPH 12H 06/1200Z 18.1N 63.1W 155 KT 180 MPH 24H 07/0000Z 19.1N 65.9W 150 KT 175 MPH 36H 07/1200Z 20.1N 68.5W 145 KT 165 MPH 48H 08/0000Z 21.0N 71.2W 140 KT 160 MPH 72H 09/0000Z 22.0N 76.2W 135 KT 155 MPH 96H 10/0000Z 23.2N 79.5W 125 KT 145 MPH 120H 11/0000Z 25.0N 81.5W 120 KT 140 MPH $$ Forecaster Pasch

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Tropical Storm Jose Forecast Discussion Number 3

2017-09-06 04:31:35| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Sep 05 2017 000 WTNT42 KNHC 060231 TCDAT2 Tropical Storm Jose Discussion Number 3 NWS National Hurricane Center Miami FL AL122017 1100 PM AST Tue Sep 05 2017 Jose continues to gradually strengthen. Geostationary and microwave satellite images indicate that the center of the system is located on the north side of the main area of deep convection. Fragmented curved bands also exist to the north of the center. The initial intensity is nudged upward to 45 kt, based on a recent ASCAT pass. This wind speed estimate is also in agreement with a T3.0/45 kt Dvorak classification from TAFB and similar ADT values from CIMSS at the University of Wisconsin. Satellite fixes suggest that Jose is moving westward at 12 kt. A slightly faster westward to west-northwestward motion is expected during the next 3 days while Jose moves in the flow on the south and southwest sides of a subtropical high. After that time, a slower northwestward motion is forecast when Jose moves into a weakness in the ridge. Although the models agree on the overall scenario, there is a considerable amount of spread in the 4 to 5 day period on when and where Jose makes the northwest turn. The NHC official track forecast is near the middle of the guidance envelope, in best agreement with the various consensus models. The tropical storm is expected to remain in conducive environmental conditions for strengthening during the next few days, and Jose will likely become a hurricane in about 24 hours and could be near major hurricane strength by 72 hours. Thereafter, an increase in northerly shear and some drier air should end the strengthening trend and cause some weakening. The NHC intensity follows the ICON and HCCA consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 12.3N 41.7W 45 KT 50 MPH 12H 06/1200Z 12.8N 43.7W 55 KT 65 MPH 24H 07/0000Z 13.5N 46.5W 65 KT 75 MPH 36H 07/1200Z 14.2N 49.6W 75 KT 85 MPH 48H 08/0000Z 14.9N 52.6W 85 KT 100 MPH 72H 09/0000Z 16.7N 57.0W 95 KT 110 MPH 96H 10/0000Z 19.2N 59.9W 90 KT 105 MPH 120H 11/0000Z 22.4N 62.8W 80 KT 90 MPH $$ Forecaster Cangialosi

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Hurricane Irma Forecast Discussion Number 27

2017-09-05 22:53:05| National Hurricane Center (Atlantic)

Issued at 500 PM AST Tue Sep 05 2017 000 WTNT41 KNHC 052052 TCDAT1 Hurricane Irma Discussion Number 27 NWS National Hurricane Center Miami FL AL112017 500 PM AST Tue Sep 05 2017 Irma continues to exhibit a remarkably impressive satellite presentation. The intensity was increased to 160 kt on the 1800 UTC intermediate public advisory based on a couple of SFMR winds of 160 kt measured in the northeastern eyewall by the Air Force aircraft just prior to that time. The minimum pressure measured by a dropsonde in the eye was 926 mb. Irma becomes only the fifth Atlantic basin hurricane with a peak wind speed of 160 kt or higher. The others are Allen (1980), the Labor Day Hurricane of 1935, Gilbert (1988), and Wilma (2005). The eye of Irma is within range of the Meteo France radar in the northeastern Caribbean, and recent images show the development of an outer eyewall, likely the beginning stages of an eyewall replacement. These changes in inner-core structure will likely result in fluctuations in intensity during the next couple of days. Otherwise, increasing upper-ocean heat content and a very favorable upper-level pattern are expected to allow Irma to remain a category 4 or 5 hurricane during the next several days. Once again, the NHC forecast shows limited interaction of the hurricane with the islands of the Greater Antilles. Fixes from the latest satellite and radar imagery suggest that Irma is moving a little north of due west or 280/13 kt. A strong ridge extending southwestward from the central Atlantic is expected to steer Irma west-northwestward during the couple of days. A large mid-latitude trough over the eastern United States is forecast to lift northeastward, allowing the ridge to build westward and keep Irma on a westward to west-northwestward heading through Friday. Over the weekend, a shortwave trough diving southward over the east-central U.S. is expected to weaken the western portion of the ridge, causing Irma to turn poleward. The dynamical model guidance is in good agreement through 72 hours, but there is increasing spread thereafter. The HWRF, UKMET, and ECMWF show a more southerly track and a sharper turn around day 5, while the GFS is farther north and east late in the period. The NHC track is near a consensus of these models and close to the HFIP corrected consensus. Users are reminded to not focus on the exact forecast track, especially at the longer ranges, since the average NHC track errors are about 175 and 225 statute miles at days 4 and 5, respectively. KEY MESSAGES: 1. Irma is a potentially catastrophic category 5 hurricane and will bring life-threatening wind, storm surge, and rainfall hazards to portions of the northeastern Leeward Islands tonight and tomorrow. These hazards will spread into the Virgin Islands and Puerto Rico tomorrow. Preparations should be rushed to completion before the arrival of tropical-storm force winds tomorrow morning in Virgin Islands and Puerto Rico. 2. A hurricane warning is in effect for the northern coast of the Dominican Republic, with hurricane watches for Haiti, the southeastern Bahamas and the Turks and Caicos. Irma is likely to bring dangerous wind, storm surge, and rainfall to these areas from Wednesday night through Friday. 3. Irma could directly affect the remainder of the Bahamas and Cuba as an extremely dangerous major hurricane later this week. Residents in these areas should monitor the progress of Irma and listen to advice given by officials. 4. The chance of direct impacts from Irma beginning later this week and this weekend from wind, storm surge, and rainfall continues to increase in the Florida Keys and portions of the Florida Peninsula. However, it is too soon to specify the timing and magnitude of these impacts. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 17.1N 59.8W 160 KT 185 MPH 12H 06/0600Z 17.6N 61.8W 155 KT 180 MPH 24H 06/1800Z 18.5N 64.6W 150 KT 175 MPH 36H 07/0600Z 19.5N 67.3W 145 KT 165 MPH 48H 07/1800Z 20.4N 70.1W 140 KT 160 MPH 72H 08/1800Z 21.6N 75.3W 135 KT 155 MPH 96H 09/1800Z 22.7N 79.3W 125 KT 145 MPH 120H 10/1800Z 24.4N 81.5W 120 KT 140 MPH $$ Forecaster Brown

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Tropical Depression Thirteen Forecast Discussion Number 1

2017-09-05 22:38:37| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Tue Sep 05 2017 000 WTNT43 KNHC 052038 TCDAT3 Tropical Depression Thirteen Discussion Number 1 NWS National Hurricane Center Miami FL AL132017 400 PM CDT Tue Sep 05 2017 The small area of low pressure in the southwestern Gulf of Mexico has become better organized during the past several hours, with deep convection forming over the center. ASCAT data showed a well-defined circulation with winds of about 30 kt. Thus, a tropical depression has formed, with maximum winds estimated at 30 kt. While the cyclone is currently experiencing westerly shear, most of the guidance indicate the shear should gradually lessen. Combined with the very warm Gulf of Mexico waters, this should promote strengthening. The shear could increase again in a few days, so the intensity forecast will be leveled off at that time. The NHC wind speed prediction is near or slightly higher than the model consensus, but could be conservative. The depression has been drifting eastward during the day. For the next couple of days, the cyclone isn't expected to move much as it is caught in an area of light winds in the mid-levels. By Friday, a ridge should build over Texas and the northwestern Gulf of Mexico, which is likely to steer the system southwestward at a faster pace. The NHC forecast is on the southern side of the guidance, since models in that area tend to have a northward bias, between the corrected consensus and the ECMWF. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 22.4N 96.7W 30 KT 35 MPH 12H 06/0600Z 22.4N 96.3W 35 KT 40 MPH 24H 06/1800Z 22.2N 95.6W 45 KT 50 MPH 36H 07/0600Z 21.8N 95.2W 50 KT 60 MPH 48H 07/1800Z 21.4N 95.2W 55 KT 65 MPH 72H 08/1800Z 20.9N 95.6W 55 KT 65 MPH 96H 09/1800Z 19.7N 97.2W 30 KT 35 MPH...INLAND 120H 10/1800Z...DISSIPATED $$ Forecaster Blake

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