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Hurricane Dorian Forecast Discussion Number 38

2019-09-02 22:46:14| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Mon Sep 02 2019 000 WTNT45 KNHC 022046 TCDAT5 Hurricane Dorian Discussion Number 38 NWS National Hurricane Center Miami FL AL052019 500 PM EDT Mon Sep 02 2019 Dorian remains an impressive hurricane in satellite imagery. Recent radar and aircraft observations are again showing signs of a concentric eyewall structure which might be one of the factors that has led to a decrease in the peak winds and a small expansion of the wind field. An Air Force Reserve Hurricane Hunter aircraft reported peak flight-level winds of 129 kt, SFMR winds of 121 kt, and a central pressure that has risen to 940 mb. Based on these observations, the initial wind speed has been set at 125 kt. Some additional decrease in wind speed is likely in the short term due due to a possible eyewall replacement and upwelling of cooler waters caused by the very slow motion of the hurricane. Although some additional slow weakening is forecast while the hurricane moves northward along the southeastern United States coastline due to increasing southwesterly shear, Dorian is forecast to remain a powerful hurricane during that time. The NHC intensity forecast forecast is a blend of the latest statistical and and consensus model guidance. Dorian has become nearly stationary this afternoon with the two most recent aircraft fixes showing essentially no motion. A slow westward to west-northwestward motion should resume overnight and continue into early Tuesday, with the eye and devastating winds only slowly pulling away from Grand Bahama Island. By Tuesday afternoon, Dorian should begin its much anticipated northwestward turn as a weakness becomes more pronounced in the subtropical ridge. Although the center of Dorian is forecast to move near, but parallel to, the Florida east coast, only a small deviation of the track toward the west would bring the core of the hurricane onshore. A broad mid- latitude trough should help turn Dorian northeastward by Wednesday night, and the track models show the center coming precariously close to the southeastern United States coast. The tracks from the 1200 UTC runs of the global models have remained fairly stable, which has resulted in little overall change to the latest NHC track forecast. Users are reminded that the hurricane is not a point, and that life-threatening storm surge and hurricane-force winds extend far from the center. Regardless of the exact forecast track, strong winds and a life-threatening storm surge are likely along a portion of the U.S east coast from Florida through the Carolinas. Key Messages: 1. Devastating winds and storm surge will continue to affect Grand Bahama Island through tonight. Everyone there should remain in shelter and not venture into the eye. 2. Life-threatening storm surge and dangerous hurricane-force winds are expected along portions of the Florida east coast and the coasts of Georgia and South Carolina, regardless of the exact track of Dorian's center. Water levels could begin to rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 3. The risk of life-threatening storm surge and hurricane-force winds continues to increase along the coast North Carolina. Residents in these areas should follow advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the southeast and lower mid-Atlantic regions of the United States through Friday. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 26.8N 78.4W 125 KT 145 MPH 12H 03/0600Z 27.0N 78.7W 115 KT 130 MPH 24H 03/1800Z 27.6N 79.1W 110 KT 125 MPH 36H 04/0600Z 28.7N 79.7W 110 KT 125 MPH 48H 04/1800Z 30.0N 80.1W 105 KT 120 MPH 72H 05/1800Z 32.8N 78.6W 95 KT 110 MPH 96H 06/1800Z 36.6N 73.1W 80 KT 90 MPH 120H 07/1800Z 43.5N 64.0W 75 KT 85 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Hurricane Juliette Forecast Discussion Number 7

2019-09-02 22:36:11| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Mon Sep 02 2019 000 WTPZ41 KNHC 022036 TCDEP1 Hurricane Juliette Discussion Number 7 NWS National Hurricane Center Miami FL EP112019 300 PM MDT Mon Sep 02 2019 Juliette is clearly on the upswing. A banding eye is present in visible and IR imagery, and satellite intensity estimates around 1800 UTC were all near 65 kt. The IR presentation of the cyclone has continued to improve since then and the initial intensity has been raised to 70 kt, making making Juliette the 5th hurricane of the eastern North Pacific season, and the first hurricane in that basin since July 31. The hurricane has quickly strengthened today and I see no reason why this won't continue for the next 12 to 24 hours. Rapid intensification still seems like a distinct possibility, though the intensity guidance certainly suggests otherwise. It is surprising that none of the guidance shows Juliette strengthening very quickly during the next day or two despite the apparent favorable environment the hurricane is embedded within and the current intensification trend. The NHC forecast remains above all of the intensity models for the first 48 hours, given the impressive structure of the hurricane. Beyond that time, the forecast is again close to the multi-model consensus and shows Juliette weakening quickly as it moves over cooler SSTs and into a dry environment. Juliette has slowed down and the initial motion is now 305/10 kt. There is no change in the forecast reasoning, and Juliette is still generally expected to be steered west-northwestward by an extensive deep-layer ridge located to the north and northeast of the cyclone. The models remain in very good agreement on the forecast of Juliette for the first 3 or 4 days of the forecast, and confidence remains high through that period. The global models then vary on the strength of the ridge and the model spread is notably higher by the end of the forecast. For now, the NHC forecast continues to split the various models and closely follows the multi-model consensus at all times. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 17.2N 113.3W 70 KT 80 MPH 12H 03/0600Z 17.9N 114.4W 80 KT 90 MPH 24H 03/1800Z 18.6N 115.9W 90 KT 105 MPH 36H 04/0600Z 19.1N 117.2W 90 KT 105 MPH 48H 04/1800Z 19.6N 118.7W 85 KT 100 MPH 72H 05/1800Z 21.1N 122.4W 65 KT 75 MPH 96H 06/1800Z 22.5N 127.0W 45 KT 50 MPH 120H 07/1800Z 24.0N 131.0W 35 KT 40 MPH $$ Forecaster Zelinsky

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Hurricane Dorian Forecast Discussion Number 37

2019-09-02 17:24:40| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Mon Sep 02 2019 000 WTNT45 KNHC 021524 CCA TCDAT5 Hurricane Dorian Discussion Number 37...Correction NWS National Hurricane Center Miami FL AL052019 1100 AM EDT Mon Sep 02 2019 Corrected missing word in last sentence Satellite and radar imagery show that Dorian is moving very slowly over Grand Bahama Island this morning. The hurricane remains quite symmetric and still exhibits a very well-defined eye, but there is somewhat less evidence of concentric eyewalls in Bahamas radar imagery. Satellite intensity estimates from UW/CIMSS, SAB, and TAFB are slightly lower this morning, and the initial intensity has been reduced to 135 kt. As Dorian moves very slowly during the next 24 hours, some upwelling in the deeper waters around the Bahamas could cause some gradual weakening. After that time, the hurricane is expected to experience a gradual increase in southwesterly shear, which should lead to a slow decrease in wind speed. However, Dorian is forecast to remain a very powerful hurricane while it moves near the southeastern United States coast. The NHC intensity forecast is close to the statistical guidance during the first day or so, then near the HFIP corrected consensus model later in the period. As anticipated, the ridge to the north of the storm has weakened and the eye of Dorian has only been inching westward this morning. The hurricane is expected to drift westward or west-northwestward over the next 24 hours, which will cause a prolonged period of devastating winds and storm surge over Grand Bahama Island. By late Tuesday, the weakness in the ridge becomes more pronounced and Dorian should turn northwestward near the east coast of the Florida. By day 3, the hurricane is expected to make a northeastward turn ahead of a broad mid-latitude trough. The overall track envelope has not changed much, and little adjustment to the previous NHC forecast was required. It cannot be stressed enough that only a small deviation to the left of the NHC forecast could bring the core of the extremely dangerous hurricane onshore of the Florida east coast within the hurricane warning area. In addition, Dorian's wind field is predicted to expand, which would bring hurricane-force winds closer to the east coast of Florida even if the track does not change. Key Messages: 1. A prolonged period of catastrophic winds and storm surge will continue to affect Grand Bahama Island through today and tonight. Everyone there should remain in shelter and not venture into the eye. 2. Life-threatening storm surge and dangerous hurricane-force winds are expected along portions of the Florida east coast and Georgia coast, regardless of the exact track of Dorian's center. Water levels could begin to rise well in advance of the arrival of strong winds. Residents in these areas should follow advice given by local emergency officials. 3. The risk of life-threatening storm surge and hurricane-force winds continues to increase along the coasts of South Carolina and North Carolina. Residents in these areas should follow advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the Southeast and lower Mid-Atlantic regions of the United States into Friday. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 26.8N 78.3W 135 KT 155 MPH 12H 03/0000Z 26.9N 78.7W 130 KT 150 MPH 24H 03/1200Z 27.2N 79.1W 125 KT 145 MPH 36H 04/0000Z 28.1N 79.6W 115 KT 130 MPH 48H 04/1200Z 29.3N 80.2W 110 KT 125 MPH 72H 05/1200Z 32.0N 79.4W 95 KT 110 MPH 96H 06/1200Z 35.4N 75.1W 85 KT 100 MPH 120H 07/1200Z 40.7N 66.8W 75 KT 85 MPH...POST-TROP/EXTRATROP $$ Forecaster Brown

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Tropical Storm Juliette Forecast Discussion Number 6

2019-09-02 16:41:39| National Hurricane Center (East Pacific)

Issued at 900 AM MDT Mon Sep 02 2019 000 WTPZ41 KNHC 021441 TCDEP1 Tropical Storm Juliette Discussion Number 6 NWS National Hurricane Center Miami FL EP112019 900 AM MDT Mon Sep 02 2019 Juliette is nearing hurricane strength. An increase in deep convection that was noted with the previous advisory has persisted, and recent microwave data shows that the cyclone has developed a well-defined inner-core. Given the observed increase in Juliette's organization, the initial intensity has been increased to 60 kt, which is supported by the latest UW-CIMSS ADT and SATCON fixes. Juliette is forecast to quickly strengthen today, and rapid intensification is a real possibility during the next 24 hours or so given the seemingly favorable environment and the presence of an low- to mid-level eye in recent microwave data. Beyond 48 h, the cyclone should begin to weaken as it moves over cooler SSTs and encounters a drier surrounding environment. The NHC intensity forecast is near the multi-model consensus from 72 h through the end of the period, but there is a fair amount of uncertainty as to how quickly Juliette will weaken since it will be moving along a sharp SST gradient. A track farther north than the NHC forecast would likely cause Juliette to weaken faster than anticipated, while a farther south track could allow it to maintain its strength for longer. Very little change was made to the track forecast. A deep-layer ridge to the northeast of Juliette should keep it on a generally west-northwestward to northwestward heading for the next 3 or 4 days days. The track guidance is particularly tightly clustered through that period and confidence in the forecast is high. The ridge could amplify by day 5 and cause Juliette to turn westward, as shown most notably by the ECMWF, though confidence is a little lower at that time. The NHC forecast is very near TVCE and HCCA at all times and lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 16.7N 112.6W 60 KT 70 MPH 12H 03/0000Z 17.6N 114.0W 75 KT 85 MPH 24H 03/1200Z 18.4N 115.5W 85 KT 100 MPH 36H 04/0000Z 18.9N 116.8W 90 KT 105 MPH 48H 04/1200Z 19.4N 118.2W 90 KT 105 MPH 72H 05/1200Z 20.6N 121.8W 70 KT 80 MPH 96H 06/1200Z 22.5N 126.0W 55 KT 65 MPH 120H 07/1200Z 23.5N 130.5W 45 KT 50 MPH $$ Forecaster Zelinsky

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Hurricane Dorian Forecast Discussion Number 36

2019-09-02 10:52:37| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Mon Sep 02 2019 000 WTNT45 KNHC 020852 TCDAT5 Hurricane Dorian Discussion Number 36 NWS National Hurricane Center Miami FL AL052019 500 AM EDT Mon Sep 02 2019 Satellite imagery continues to show that Dorian has an extremely well-defined eye embedded within very cold cloud tops. The diameter of the eye appears to have expanded to near 20 n mi, and radar data, especially from the Bahamas Department of Meteorology radar, show that there are concentric eyewalls. The hurricane also continues to exhibit strong upper-tropospheric outflow. The initial intensity estimate has been reduced to 145 kt, which lies between earlier Hurricane Hunter estimates and satellite intensity estimates from TAFB and SAB. This lowering of intensity is consistent with the development of a concentric eyewall. During the next few days, Dorian should be encountering some increase in shear, which will likely result in weakening. However it is anticipated that the system will remain a dangerous major hurricane for the next several days. The official intensity forecast lies between the statistical-dynamical guidance and the corrected multi-model consensus. Steering currents have weakened, and Dorian has almost come to a standstill over eastern Grand Bahama Island, with an initial motion of 270/1 kt. The mid-tropospheric high to the north of the hurricane that had been steering Dorian westward has collapsed. Global models indicate that, in a couple of days, a weakness in the ridge will develop along 75W-80W. This would likely cause Dorian to move northwestward to northward toward and through this weakness. Later in the forecast period, the system is expected to accelerate northeastward on the southern side of a broad mid-tropospheric trough. The official track forecast is very close to the previous one and to the corrected dynamical model consensus, HCCA. Although the official forecast does not show Dorian making landfall along the Florida east coast, it is still possible for the hurricane to deviate from this forecast, and move very near or over the coast. Users are reminded not to focus on the exact forecast track. Key Messages: 1. A prolonged period of catastrophic winds and storm surge will continue to affect Grand Bahama Island through today and tonight. Everyone there should remain in shelter and not venture into the eye. 2. Life-threatening storm surges and dangerous hurricane-force winds are expected along portions of the Florida east coast through mid-week, and storm surge and hurricane warnings are in effect. Only a slight deviation to the left of the official forecast would bring the core of Dorian near or over the Florida east coast. Residents should listen to advice given by local emergency officials. 3. There is an increasing likelihood of strong winds and dangerous storm surge along the coasts of Georgia, South Carolina, and North Carolina later this week. Residents in these areas should continue to monitor the progress of Dorian and listen to advice given by local emergency officials. 4. Heavy rains, capable of producing life-threatening flash floods, are expected over northern portions of the Bahamas and coastal sections of the Southeast and lower Mid-Atlantic regions of the United States into Friday. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 26.6N 78.2W 145 KT 165 MPH 12H 02/1800Z 26.7N 78.7W 140 KT 160 MPH 24H 03/0600Z 26.9N 79.0W 130 KT 150 MPH 36H 03/1800Z 27.6N 79.5W 120 KT 140 MPH 48H 04/0600Z 28.7N 80.0W 110 KT 125 MPH 72H 05/0600Z 31.3N 79.8W 100 KT 115 MPH 96H 06/0600Z 34.5N 76.5W 85 KT 100 MPH 120H 07/0600Z 38.5N 70.0W 75 KT 85 MPH $$ Forecaster Pasch

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