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Tropical Storm Harvey Forecast Discussion Number 26

2017-08-26 22:37:24| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Sat Aug 26 2017 000 WTNT44 KNHC 262037 TCDAT4 Tropical Storm Harvey Discussion Number 26 NWS National Hurricane Center Miami FL AL092017 400 PM CDT Sat Aug 26 2017 Harvey has continued to weaken while located inland over Texas. Doppler radar data indicate that winds are now 55 kt, and since there are no surface observations near the center, this is the intensity used in this advisory. A continued weakening is anticipated, and the NHC forecast uses the trend provided by the SHIPS decay model. However, if a large portion of Harvey's circulation remains over the Gulf of Mexico, the cyclone could weaken at a slower rate than shown here. Harvey has barely moved during the past few hours and little motion is anticipated. Since the steering currents are forecast to remain light, Harvey could easily meander for the next 4 to 5 days over southeast Texas as indicated in the NHC forecast. Guidance disagrees in which direction the cyclone will move, but all the models agree that any motion will be quite slow. Key Messages: 1. While Harvey's winds are decreasing, life-threatening hazards will continue from heavy rainfall over much of southeastern Texas and from storm surge along portions of the Texas coast. 2. Catastrophic and life-threatening flooding is expected across the middle and upper Texas coast from additional rainfall of 15 to 25 inches, with isolated storm totals as high as 40 inches, through Thursday. Please heed the advice of local officials and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 3. A Storm Surge Warning remains in effect for portions of the Texas coast. Life-threatening storm surge flooding will be slow to recede due to the slow motion of Harvey and a prolonged period of onshore flow. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 29.1N 97.6W 55 KT 65 MPH...INLAND 12H 27/0600Z 29.1N 97.6W 45 KT 50 MPH...INLAND 24H 27/1800Z 28.9N 97.7W 35 KT 40 MPH...INLAND 36H 28/0600Z 28.5N 97.3W 30 KT 35 MPH...INLAND 48H 28/1800Z 28.3N 97.1W 30 KT 35 MPH...INLAND 72H 29/1800Z 28.7N 97.0W 30 KT 35 MPH...INLAND 96H 30/1800Z 29.5N 97.0W 30 KT 35 MPH...INLAND 120H 31/1800Z 30.5N 97.0W 30 KT 35 MPH...INLAND $$ Forecaster Avila

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Hurricane Harvey Forecast Discussion Number 25

2017-08-26 16:52:50| National Hurricane Center (Atlantic)

Issued at 1000 AM CDT Sat Aug 26 2017 000 WTNT44 KNHC 261452 TCDAT4 Hurricane Harvey Discussion Number 25 NWS National Hurricane Center Miami FL AL092017 1000 AM CDT Sat Aug 26 2017 Harvey has been inland for about 12 hours and weakening is under way. Doppler radar data indicate that winds have decreased to 65 kt, and that is the intensity used in this advisory. Since Harvey is over land, a continued weakening is anticipated, and the NHC forecast uses the trend provided by the SHIPS decay model. However, if a portion of Harvey's circulation remains over the Gulf of Mexico, the cyclone could weaken at a slower rate than shown here. The hurricane is moving very slowly toward the north at about 2 kt. Harvey is embedded within very light steering currents, and global models keep this weak flow in place for the next several days. Based on this pattern, Harvey could easily meander for the next 4 to 5 days over southeast Texas as indicated in the NHC forecast. The only agreement among the track guidance is that Harvey is certainly not going anywhere fast. This slow motion of the cyclone is expected to exacerbate the potential for catastrophic flooding from heavy rainfall at least through the middle of next week. Please note that hourly Tropical Cyclone Updates (TCUs) have been discontinued due to the degradation of Harvey's center on radar. Key Messages: 1. While Harvey's winds have begun to weaken, life-threatening hazards will continue from heavy rainfall over much of southeastern Texas and from storm surge along portions of the Texas coast. 2. Catastrophic and life-threatening flooding is expected across the middle and upper Texas coast from heavy rainfall of 15 to 30 inches, with isolated amounts as high as 40 inches, through Thursday. Please heed the advice of local officials and do not drive into flooded roadways. Refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. A summary of rainfall totals compiled by the Weather Prediction Center can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html 3. A Storm Surge Warning remains in effect for portions of the Texas. Life-threatening storm surge flooding will be slow to recede due to the slow motion of Harvey and a prolonged period of onshore flow. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. FORECAST POSITIONS AND MAX WINDS INIT 26/1500Z 28.9N 97.3W 65 KT 75 MPH...INLAND 12H 27/0000Z 29.1N 97.4W 45 KT 50 MPH...INLAND 24H 27/1200Z 29.2N 97.5W 40 KT 45 MPH...INLAND 36H 28/0000Z 29.0N 97.5W 35 KT 40 MPH...INLAND 48H 28/1200Z 28.7N 97.0W 30 KT 35 MPH...INLAND 72H 29/1200Z 28.7N 96.7W 30 KT 35 MPH...INLAND 96H 30/1200Z 29.5N 96.7W 30 KT 35 MPH...INLAND 120H 31/1200Z 30.5N 96.5W 30 KT 35 MPH...INLAND $$ Forecaster Avila/Lapenta

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Hurricane Harvey Forecast Discussion Number 24

2017-08-26 10:55:21| National Hurricane Center (Atlantic)

Issued at 400 AM CDT Sat Aug 26 2017 000 WTNT44 KNHC 260855 TCDAT4 Hurricane Harvey Discussion Number 24 NWS National Hurricane Center Miami FL AL092017 400 AM CDT Sat Aug 26 2017 Harvey's eye has moved inland gradually during the past few hours, and maximum winds have decreased significantly since landfall. Radar velocity data from the Corpus Christi NOAA Doppler radar are showing winds as high as 90 kt at an elevation of 3000-3500 ft in the northwestern eyewall. The advisory intensity is therefore set at 85 kt, which could still be a little generous. Continued weakening is expected as Harvey's eye continues to move inland, and maximum sustained winds are likely to fall below hurricane force later today. A more gradual weakening trend is anticipated after that point, and Harvey is forecast to maintain tropical storm strength at least through day 4, especially if part of its circulation remains over water. The updated NHC intensity forecast continues a similar weakening trend noted in previous advisories and is closest to the HFIP Corrected Consensus Approach (HCCA). The initial motion has continued to decrease, and it is now estimated to be 325/5 kt. As the steering currents around Harvey continue to collapse, the cyclone is expected to stall or meander inland over southeastern Texas. Only a few models show any sort of definitive northeastward motion at the end of the forecast period, and for the most part, the most reliable models keep Harvey over southeastern Texas through day 5. The NHC track forecast depicts Harvey taking a slow counterclockwise loop just inland from the coast. This track is expected to exacerbate the potential for catastrophic flooding from heavy rainfall at least through the middle of next week. Key Messages: 1. Harvey is moving farther inland over southeastern Texas and continues to bring life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast. 2. A Storm Surge Warning is in effect for much of the Texas coast. Life-threatening storm surge flooding could still reach heights of 6 to 12 feet above ground level at the coast between Port Aransas and Port O'Connor. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. Due to the slow motion of Harvey and a prolonged period of onshore flow, water levels will remain elevated for several days. 3. Catastrophic and life-threatening flooding is expected across the middle and upper Texas coast from heavy rainfall of 15 to 30 inches, with isolated amounts as high as 40 inches, through Wednesday. Please refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 28.5N 97.2W 85 KT 100 MPH...INLAND 12H 26/1800Z 28.8N 97.4W 70 KT 80 MPH...INLAND 24H 27/0600Z 29.0N 97.6W 50 KT 60 MPH...INLAND 36H 27/1800Z 28.7N 97.6W 45 KT 50 MPH...INLAND 48H 28/0600Z 28.5N 97.3W 40 KT 45 MPH...INLAND 72H 29/0600Z 28.3N 96.8W 35 KT 40 MPH...INLAND 96H 30/0600Z 29.0N 96.5W 35 KT 40 MPH...INLAND 120H 31/0600Z 30.0N 96.5W 30 KT 35 MPH...INLAND $$ Forecaster Berg

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Hurricane Harvey Forecast Discussion Number 23

2017-08-26 05:01:48| National Hurricane Center (Atlantic)

Issued at 1000 PM CDT Fri Aug 25 2017 000 WTNT44 KNHC 260301 TCDAT4 Hurricane Harvey Discussion Number 23 NWS National Hurricane Center Miami FL AL092017 1000 PM CDT Fri Aug 25 2017 Harvey has continued to slowly strengthen since the last advisory. Air Force Reserve Hurricane Hunter aircraft data earlier indicated 700-mb flight-level winds near 130 kt, and there have been multiple estimates from the Stepped Frequency Microwave Radiometer of winds of 110-115 kt. In addition, there have been winds of 135-150 kt observed at 2500-3000 ft in the north eyewall by the Corpus Christi WSR-88D. Based on these, Harvey is making landfall at this time as a category 4 hurricane with winds near 115 kt. The initial motion is 325/6, a little slower than before. The eye of Harvey should continue this general motion for the next several hours, which would bring it inland over southeastern Texas. After 12 h or so, the hurricane should become embedded in an area of weak steering currents and become nearly stationary. The track guidance is in good agreement that Harvey will move slowly through at least 72 h, and the new forecast track shows a slow cyclonic loop during that time. After 72 h, an equally slow motion toward the north or northeast appears likely. It is unclear at this time whether the center of Harvey will emerge over the Gulf of Mexico, as the guidance is in poor agreement on that. It is clear, though, that Harvey will remain over southeastern Texas or the adjacent waters through the forecast period, thus producing a major rainfall and flooding threat. Gradual weakening is now anticipated as Harvey moves farther inland. However, a large amount of the circulation should remain over the Gulf of Mexico, and the weakening is likely to be slower than normal. The new intensity forecast is slightly changed from the previous forecast, but it still calls for Harvey to remain a hurricane through 24 h and remain a tropical storm through the forecast period. The forecast is based on the premise that the center will remain over land, and the intensities could be higher if the center emerges over the Gulf of Mexico. Key Messages: 1. Harvey is making landfall at this time, bringing life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast. Hurricane conditions have been reported in the landfall area. 2. A Storm Surge Warning is in effect for much of the Texas coast. Life-threatening storm surge flooding could reach heights of 9 to 13 feet above ground level at the coast between Port Aransas and Port O'Connor. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. Due to the slow motion of Harvey and a prolonged period of onshore flow, water levels will remain elevated for several days. 3. Catastrophic and life-threatening flooding is expected across the middle and upper Texas coast from heavy rainfall of 15 to 30 inches, with isolated amounts as high as 40 inches, through Wednesday. Please refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. FORECAST POSITIONS AND MAX WINDS INIT 26/0300Z 28.0N 97.0W 115 KT 130 MPH...ON COAST 12H 26/1200Z 28.6N 97.3W 95 KT 110 MPH...INLAND 24H 27/0000Z 29.0N 97.7W 65 KT 75 MPH...INLAND 36H 27/1200Z 29.0N 97.9W 50 KT 60 MPH...INLAND 48H 28/0000Z 28.7N 97.8W 45 KT 50 MPH...INLAND 72H 29/0000Z 28.0N 97.5W 40 KT 45 MPH...INLAND 96H 30/0000Z 28.5N 96.5W 40 KT 45 MPH...INLAND 120H 31/0000Z 29.5N 96.0W 35 KT 40 MPH...INLAND $$ Forecaster Beven

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Hurricane Harvey Forecast Discussion Number 22

2017-08-25 22:55:49| National Hurricane Center (Atlantic)

Issued at 400 PM CDT Fri Aug 25 2017 000 WTNT44 KNHC 252055 TCDAT4 Hurricane Harvey Discussion Number 22 NWS National Hurricane Center Miami FL AL092017 400 PM CDT Fri Aug 25 2017 Despite its concentric eyewall structure, Harvey's winds have increased during the day. NOAA and Air Force Reserve Hurricane Hunter planes have measured maximum flight-level winds of 129 kt and SFMR winds to 102 kt. Based on these data, Harvey's maximum surface winds are estimated to be 110 kt. Harvey's central pressure has also continued to fall, and the latest estimate based on dropsonde data is 941 mb. Harvey still has not slowed down, and the initial estimate is 325/9 kt. Based on the forecast track, Harvey is expected to make landfall along the middle Texas coast tonight. After that, the track models insist that the hurricane will slow down considerably during the next 24 hours, and it is likely to move very little between 36 and 120 hours. In fact, there has been a somewhat notable change in the guidance, with very few of the models showing Harvey lifting out toward the northeast by the end of the 5-day forecast period. As a result, the NHC track forecast has been pulled back a bit and keeps Harvey near or just inland of the Texas coast through the middle of next week. This slow motion only exacerbates the heavy rainfall and flooding threat across southern and southeastern Texas. Harvey may continue to strengthen during the 6-12 hours it has before landfall, but regardless it is expected to make landfall at major hurricane strength. Gradual weakening is anticipated after the center moves inland, but Harvey's slow motion will keep a significant portion of its circulation over water, which may slow the weakening rate. As a result, the NHC intensity forecast leans closer to the global model guidance instead of the statistical- dynamical guidance, which seems to weaken Harvey too fast. Harvey could maintain tropical storm strength for the entire 5-day forecast period due to its proximity to the northwestern Gulf of Mexico. Key Messages: 1. Harvey will make landfall tonight, bringing life-threatening storm surge, rainfall, and wind hazards to portions of the Texas coast. Tropical-storm-force winds have moved onshore in portions of the warning areas and conditions will continue to deteriorate as the eye of Harvey approaches the middle Texas coast tonight. 2. A Storm Surge Warning is in effect for much of the Texas coast. Life-threatening storm surge flooding could reach heights of 6 to 12 feet above ground level at the coast between the north entrance of the Padre Island National Seashore and Sargent. For a depiction of areas at risk, see the Storm Surge Watch/Warning Graphic at hurricanes.gov. Due to the slow motion of Harvey and a prolonged period of onshore flow, water levels will remain elevated for several days. 3. Catastrophic and life-threatening flooding is expected across the middle and upper Texas coast from heavy rainfall of 15 to 30 inches, with isolated amounts as high as 40 inches, through Wednesday. Please refer to products from your local National Weather Service office and the NOAA Weather Prediction Center for more information on the flooding hazard. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 27.5N 96.5W 110 KT 125 MPH 12H 26/0600Z 28.2N 97.0W 100 KT 115 MPH...INLAND 24H 26/1800Z 28.8N 97.5W 75 KT 85 MPH...INLAND 36H 27/0600Z 28.9N 97.8W 60 KT 70 MPH...INLAND 48H 27/1800Z 28.6N 97.8W 50 KT 60 MPH...INLAND 72H 28/1800Z 28.1N 96.9W 40 KT 45 MPH...INLAND 96H 29/1800Z 28.5N 96.0W 40 KT 45 MPH...OVER WATER 120H 30/1800Z 29.5N 95.5W 35 KT 40 MPH...INLAND $$ Forecaster Berg

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