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Tropical Depression Erin Forecast Discussion Number 9
2019-08-28 22:34:35| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Wed Aug 28 2019 000 WTNT41 KNHC 282034 TCDAT1 Tropical Depression Erin Discussion Number 9 NWS National Hurricane Center Miami FL AL062019 500 PM EDT Wed Aug 28 2019 Strong northerly shear has continued to take a toll on Erin, with the system becoming a swirl of low- to mid-level clouds. The initial wind speed remains 30 kt, which is supported by earlier ASCAT data and observations from buoy 41001. Northwesterly shear should continue to prevent strengthening while the system remains over warm waters tonight. If deep convection does not return soon, the system is likely to become post-tropical. Erin or its remnants should merge with a frontal system on Thursday and it could strengthen due to baroclinic processes after that time. The new NHC intensity forecast calls for the system to become an extratropical gale in 24 hours, and is based on guidance from the NOAA Ocean Prediction Center. Erin has turned northward or 360/11 kt. The cyclone should turn north-northeastward tonight ahead of an approaching mid-latitude trough. After that time, it is expected to accelerate north-northeastward until it merges with another extratropical low by late Friday. The updated NHC track forecast is similar to the previous advisory, and lies near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 34.5N 72.7W 30 KT 35 MPH 12H 29/0600Z 36.8N 71.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 29/1800Z 40.7N 68.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 36H 30/0600Z 45.3N 64.6W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 30/1800Z 50.5N 60.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 31/1800Z...DISSIPATED $$ Forecaster Brown
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Tropical Storm Dorian Forecast Discussion Number 17
2019-08-28 17:11:11| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Aug 28 2019 000 WTNT45 KNHC 281510 CCA TCDAT5 Tropical Storm Dorian Discussion Number 17...CORRECTED NWS National Hurricane Center Miami FL AL052019 1100 AM AST Wed Aug 28 2019 Corrected day 5 intensity forecast in table. Satellite and radar images indicate that the cloud pattern has become better organized during the past several hours. This was confirmed by data from an Air Force reconnaissance plane currently investigating Dorian, which reported a flight-level wind of 72 kt and a peak SFMR value of 60 kt. The estimated central pressure was 999 mb in the last fix. On this basis the initial intensity has been adjusted upward to 60 kt. Only a slow strengthening is anticipated today while Dorian is moving through the U.S. and British Virgin Islands. However, once the cyclone reaches the western Atlantic well east of the Bahamas, it will encounter a favorable environment of low shear and warm waters, resulting in a more marked intensification. The NHC foreast is more aggressive than the previous one, and brings Dorian to category 3 intensity by the end of the period. This forecast very closely follows the intensity consensus, the HCCA model, and the SHIPS guidance. Fixes from the reconnaissance plane indicate that Dorian has been moving toward the northwest or 315 degrees at 11 kt. The cyclone is heading toward a weakness in the Atlantic subtropical ridge, and this motion should continue for the next 2 to 3 days. However, after that time, all global models build a robust ridge over the western Atlantic, and this flow pattern should force Dorian to turn more to the west-northwest toward Florida and the southeast coast of the United States. All indications are that by this Labor Day weekend, a powerful hurricane will be near the Florida or southeastern coast of the United States. The new NHC track forecast is not significantly different from the previous one, and it very closely follows the multi-model consensus TVCA and the HCCA. Users are reminded not to focus on the exact forecast track, as the average 5-day track error is around 200 miles. Key Messages: 1. Hurricane conditions are expected in the U.S. and British Virgin Islands, Culebra, and Vieques today. Tropical storm conditions are expected in Puerto Rico today with hurricane conditions possible. 2. Heavy rainfall over portions of Puerto Rico and the U.S. and British Virgin Islands could produce flash flooding during the next couple of days. Heavy rains are expected to occur over portions of the Bahamas, Florida, and elsewhere in the southeastern Untied States later this week and into early next week. 3. The risk of dangerous storm surge and hurricane-force winds is increasing in the central and northwestern Bahamas and along the Florida east coast, although it is too soon to determine where these hazards will occur. Residents in these areas should ensure that they have their hurricane plan in place and not focus on the exact forecast track of Dorian's center. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 17.5N 64.5W 60 KT 70 MPH 12H 29/0000Z 18.7N 65.7W 65 KT 75 MPH 24H 29/1200Z 20.5N 67.0W 65 KT 75 MPH 36H 30/0000Z 22.4N 68.4W 70 KT 80 MPH 48H 30/1200Z 24.2N 69.9W 75 KT 85 MPH 72H 31/1200Z 26.5N 74.0W 90 KT 105 MPH 96H 01/1200Z 27.7N 77.7W 100 KT 115 MPH 120H 02/1200Z 28.6N 80.3W 100 KT 115 MPH $$ Forecaster Avila
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Tropical Depression Erin Forecast Discussion Number 8
2019-08-28 16:36:35| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Wed Aug 28 2019 000 WTNT41 KNHC 281436 TCDAT1 Tropical Depression Erin Discussion Number 8 NWS National Hurricane Center Miami FL AL062019 1100 AM EDT Wed Aug 28 2019 Erin has become less organized this morning with the center exposed and becoming more removed from the remaining deep convection. Satellite intensity estimates have decreased and a blend of these support an initial wind speed of 30 kt. The northwesterly shear that has been affecting Erin is forecast to decrease somewhat later today and tonight, but given the current structure of the system, little overall change in intensity is anticipated during that time. If convection does not re-develop closer to the center later today, Erin could become post-tropical. An alternate scenario is for the circulation to become elongated and lose definition as a mid- latitude trough approaches from the west. The global models suggest that the trough is likely to help Erin or its remnants deepen somewhat as an extratropical low on Thursday. The NHC intensity forecast follows suit and shows little change in strength today, then indicates that Erin or its remnants will become an extratropical gale by 36 hours. Erin is now moving north-northwestward at 11 kt. The dynamical model guidance is in good agreement on Erin turning northward and then northeastward by Thursday ahead of the aforementioned mid-latitude trough. Erin or its remnants are forecast to accelerate and reach Nova Scotia in about 36 hours. The guidance envelope has shifted slightly westward, and the updated official forecast has been adjusted accordingly. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 33.6N 72.8W 30 KT 35 MPH 12H 29/0000Z 35.5N 72.3W 30 KT 35 MPH 24H 29/1200Z 39.0N 70.2W 30 KT 35 MPH 36H 30/0000Z 43.8N 66.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 30/1200Z 48.9N 62.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 31/1200Z...DISSIPATED $$ Forecaster Brown
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Tropical Storm Dorian Forecast Discussion Number 16
2019-08-28 10:48:59| National Hurricane Center (Atlantic)
Issued at 500 AM AST Wed Aug 28 2019 000 WTNT45 KNHC 280848 TCDAT5 Tropical Storm Dorian Discussion Number 16 NWS National Hurricane Center Miami FL AL052019 500 AM AST Wed Aug 28 2019 Satellite images and Doppler radar data from Puerto Rico indicate that Dorian is becoming better organized with banding features now more established on the north side of the circulation. The flight-level and SFMR winds from the Air Force Hurricane Hunters were a little higher in the most recent passes through the storm, and a blend of that data supports an initial intensity of about 50 kt. The Hurricane Hunters also reported that Dorian has developed a partial eyewall and that the minimum pressure has dropped to 1003 mb. A combination of the reconnaissance data and recent ASCAT passes were used to modify the initial wind radii, and it confirms that Dorian remains a compact and asymmetric tropical storm. Dorian is moving northwestward at 11 kt toward a weakness in the ridge caused by a cut off mid- to upper-level low to the north of Hispaniola. This motion should continue for the next few days, taking Dorian across the Virgin Islands or the eastern portion of Puerto Rico later today and to the east of the Bahamas on Thursday and Friday. By late in the week, the steering pattern is expected to change as the models show a ridge building over the western Atlantic. The flow between the ridge and the aforementioned mid- to upper-level low should cause Dorian to turn west-northwestward and approach the southeast U.S. coast this weekend. The new NHC track forecast is adjusted a little to the right at most forecast times trending toward the latest consensus aids. However, there has been considerable run-to-run variability among the models so confidence in the long term track remains low. In addition, users are reminded not to focus on the exact forecast points as the average 5-day track error is around 200 miles. Some additional slow strengthening seems likely today before Dorian reaches Puerto Rico and the Virgin Islands. The land interaction could end the strengthening trend or even cause some temporary weakening, however, environmental conditions favor intensification after the storm pulls northward into the southwestern Atlantic. Nearly all of the intensity models show Dorian becoming a hurricane in about 2 days, with additional strengthening beyond that time. The NHC intensity forecast is increased from the previous one, especially at the longer forecast times, to be in better agreement with the latest models. This forecast, however, is still on the lower end of the guidance envelope, so additional upward adjustments could be needed if the guidance trends persists. It is also worth noting that the global models show Dorian increasing in size by the time it nears the southeast U.S. Key Messages: 1. Tropical storm conditions are expected in the U.S. and British Virgin Islands and Puerto Rico today, and are possible in portions of the Dominican Republic tonight and Thursday. Hurricane conditions are possible in Puerto Rico and the U.S. Virgin Islands today. 2. Heavy rainfall over portions of Puerto Rico and the U.S. and British Virgin Islands could produce flash flooding during the next couple of days. Heavy rains are expected to occur over portions of the Bahamas and Florida later this week and into early next week. 3. The threat of tropical storm or hurricane conditions, along with storm surge, in the northwestern Bahamas and along portions of the Florida east coast have increased. Residents in these areas should monitor the progress of Dorian and ensure that they have their hurricane plan in place. 4. Uncertainty in the intensity forecast late this week remains higher than usual due to a large spread in the model guidance. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 16.8N 63.9W 50 KT 60 MPH 12H 28/1800Z 17.9N 65.3W 60 KT 70 MPH 24H 29/0600Z 19.5N 66.8W 60 KT 70 MPH 36H 29/1800Z 21.4N 68.2W 60 KT 70 MPH 48H 30/0600Z 23.3N 69.6W 65 KT 75 MPH 72H 31/0600Z 26.1N 73.0W 80 KT 90 MPH 96H 01/0600Z 27.7N 77.1W 85 KT 100 MPH 120H 02/0600Z 29.0N 80.0W 85 KT 100 MPH $$ Forecaster Cangialosi
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Tropical Storm Erin Forecast Discussion Number 7
2019-08-28 10:32:30| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Wed Aug 28 2019 000 WTNT41 KNHC 280832 TCDAT1 Tropical Storm Erin Discussion Number 7 NWS National Hurricane Center Miami FL AL062019 500 AM EDT Wed Aug 28 2019 GOES-16 shortwave infrared imagery and recent microwave overpasses show that Erin's surface center has once again become exposed to the north of a rather amorphous deep convective mass. Erin's severely tilted structure is in response to persistent moderate west-northwesterly shear, indicated in the UW-CIMSS shear product. Subjective satellite intensity estimates from TAFB and SAB support maintaining an initial intensity of 35 kt for this advisory. A series of microwave images during the past several hours indicate that the initial motion is estimated to be north-northwestward, or 330/5 kt, within the mid-level southerly flow produced by a mid-latitude shortwave trough approaching the northeastern United States, and the Bermuda high to east-southeast. A turn toward the north while accelerating is forecast later today and Erin is expected to reach Nova Scotia, with a north-northeastward heading, by the end of the week. Only a minor adjustment, a bit slower than the previous advisory, was made in order to hedge closer to the TVCA multi-model consensus. Statistical-dynamical intensity guidance show that the shear should diminish somewhat today while the system remains over warm oceanic sea surface temperatures. This, should allow for some slight strengthening at that time. Thereafter, baroclinic processes associated with the aforementioned mid-latitude trough and significantly decreasing sea surface temperatures should cause Erin to acquire extratropical characteristics, and complete the transition in 36 hours, as the Florida State Cyclone Phase Evolution forecast and global models unanimously predict. Minor adjustments were made to the forecast wind radii based on the RVCN consensus radii model. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 32.4N 72.3W 35 KT 40 MPH 12H 28/1800Z 33.9N 72.2W 40 KT 45 MPH 24H 29/0600Z 36.6N 70.8W 35 KT 40 MPH 36H 29/1800Z 40.7N 67.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 48H 30/0600Z 45.3N 63.9W 30 KT 35 MPH...POST-TROP/EXTRATROP 72H 31/0600Z...DISSIPATED $$ Forecaster Roberts
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