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Tropical Depression Harvey Forecast Discussion Number 12
2017-08-23 16:50:32| National Hurricane Center (Atlantic)
Issued at 1000 AM CDT Wed Aug 23 2017 000 WTNT44 KNHC 231450 TCDAT4 Tropical Depression Harvey Discussion Number 12 NWS National Hurricane Center Miami FL AL092017 1000 AM CDT Wed Aug 23 2017 Air Force Reserve Hurricane Hunter data indicate that Harvey has regenerated in the Bay of Campeche, with a closed circulation noted and a central pressure of about 1006 mb. The initial wind speed is 30 kt based on SFMR data from the aircraft. Harvey is not well organized at the moment, with an asymmetric cloud pattern and a large radius of maximum wind. The environment, however, is conducive for intensification while Harvey moves over the very warm Gulf of Mexico waters in light-to-moderate shear. The biggest hindrance to intensification in the short term is the poor structure. Thus the NHC forecast will only show a gradual increase in wind speed during the first day, with a more significant intensification after that time. Although not explicitly forecast below, we are anticipating Harvey being a hurricane at landfall after the 48 hour forecast point. This forecast agrees well with the guidance, almost all of which shows a quickly intensifying cyclone approaching the Texas coast. Since the center has just recently formed, the initial motion is difficult to estimate, but the long-term motion is 310/8. Harvey is expected to move more slowly toward the northwest or north- northwest as it enters a weakness in the Atlantic subtropical ridge during the next day or so. The ridge slightly strengthens by late Thursday, which should cause a faster northwestward motion by then. Around the time of landfall, however, Harvey should enter an area of weaker steering currents near the upper Texas coast as high pressure rebuilds over the southwestern United States. The storm should slow down markedly over southeast Texas, and there is considerable uncertainty on exactly how fast Harvey moves out of that state ahead of the next mid-latitude trough. For now the NHC forecast will just drift Harvey generally toward the east at days 4 and 5, on the slow side of the model consensus. Hopefully later G-IV flights and special soundings over the southern United States will help clarify the long range forecast. Key Messages: 1. Harvey is likely to bring multiple hazards to portions of the Texas coast beginning on Friday. 2. Several days of heavy rainfall are likely across portions of eastern Texas, Louisiana, and the lower Mississippi Valley from Friday through early next week. This rainfall could cause life- threatening flooding. Please refer to products from your local National Weather Service office (www.weather.gov) and the NOAA Weather Prediction Center (www.wpc.ncep.noaa.gov) for more information on the flooding hazard. 3. The National Weather Service has issued a Storm Surge Watch from Port Mansfield to High Island, Texas. There is the possibility of life-threatening inundation from rising water moving inland from the coastline during the next 48 hours in these areas. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. 4. The Potential Storm Surge Flooding Map will also be available on the NHC website by 1200 PM CDT. Remember that the Potential Storm Surge Flooding Map does not represent a forecast of expected inundation, but rather depicts a reasonable worst-case scenario - the amount of inundation that has a 10 percent chance of being exceeded at each individual location. Because the Flooding Map is based on inputs that extend out only to about 72 hours, it best represents the flooding potential in those locations within the watch area. 5. Hurricane conditions are possible along the Texas coast from Port Mansfield to San Luis Pass. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 21.5N 92.5W 30 KT 35 MPH 12H 24/0000Z 22.3N 93.2W 35 KT 40 MPH 24H 24/1200Z 23.8N 93.9W 40 KT 45 MPH 36H 25/0000Z 25.2N 94.9W 50 KT 60 MPH 48H 25/1200Z 26.7N 96.3W 60 KT 70 MPH 72H 26/1200Z 29.0N 97.3W 40 KT 45 MPH...INLAND 96H 27/1200Z 29.8N 96.9W 35 KT 40 MPH...INLAND 120H 28/1200Z 30.0N 95.0W 35 KT 40 MPH...INLAND $$ Forecaster Blake
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Tropical Storm Kenneth Forecast Discussion Number 21
2017-08-23 16:36:02| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Wed Aug 23 2017 000 WTPZ43 KNHC 231435 TCDEP3 Tropical Storm Kenneth Discussion Number 21 NWS National Hurricane Center Miami FL EP132017 800 AM PDT Wed Aug 23 2017 Practically all of Kenneth's deep convection has dissipated while the system traverses SSTs near 23 deg C. Using a blend of subjective and objective Dvorak intensity estimates yields a current intensity of 35 kt. The cyclone is likely to continue to weaken due to cool waters and strong south-southwesterly shear associated with a broad upper-level trough to its west. Kenneth should become a post-tropical cyclone in 12 to 24 hours or sooner. The latest center fixes indicate that the motion has bent a little to the left and is now around 330/10 kt. Kenneth or the post- tropical cyclone should continue to move through a break in the subtropical ridge on a generally north-northwestward heading with some deceleration over the next couple of days. Later in the forecast period, when the cyclone is likely to be very weak and shallow, a turn toward the northwest is expected following the low-level flow. The official track forecast is close to the latest HFIP Corrected Consensus prediction. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 24.6N 135.1W 35 KT 40 MPH 12H 24/0000Z 25.8N 135.7W 30 KT 35 MPH 24H 24/1200Z 27.1N 136.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 25/0000Z 28.0N 136.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 25/1200Z 28.6N 136.8W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 26/1200Z 29.7N 137.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 27/1200Z 30.7N 139.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/1200Z...DISSIPATED $$ Forecaster Pasch
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Tropical Storm Kenneth Forecast Discussion Number 20
2017-08-23 10:35:26| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Wed Aug 23 2017 000 WTPZ43 KNHC 230835 TCDEP3 Tropical Storm Kenneth Discussion Number 20 NWS National Hurricane Center Miami FL EP132017 200 AM PDT Wed Aug 23 2017 Conventional satellite imagery shows continued deterioration of Kenneth's cloud pattern. A moderate southwesterly wind shear regime and oceanic temperatures of less than 24.5C have certainly taken its toll on the cyclone. A compromise of the subjective and objective intensity estimates is the basis of lowering the initial intensity to 50 kt for this advisory. The aforementioned shear and cool water, along with a continued intruding stable air mass from the north, should result in a gradual spin down of Kenneth with weakening to a remnant low in about 24 hours, and dissipation in 5 days. The official intensity forecast follows the IVCN and Decay-SHIPS models, and reflects the previous advisory's weakening trend. The initial motion is estimated to be north-northwestward, or 340/9 kt. Kenneth should continue to move north-northwestward during the next 36-48 hours in a break in a subtropical ridge created by a high amplitude upper-level trough extending northeastward from the eastern Hawaiian Islands. Afterward, the cyclone is forecast to degenerate to a vertically shallow remnant low and move within the lower tropospheric southeasterly flow. There is some increasing spread in the global models beyond day 3. The UKMET and GFS indicate a more accelerated rate of weakening than the ECMWF. Consequently, the weaker Kenneth reflected in the UKMET/GFS decreases significantly in forward speed and turns west-northwestward in the shallow steering current while a more vertically coherent cyclone in the ECMWF continues northwestward with little reduction in speed. The NHC track forecast is a blend of both of these solutions and is very close to the HFIP Corrected Consensus model. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 23.5N 134.3W 50 KT 60 MPH 12H 23/1800Z 24.8N 135.0W 40 KT 45 MPH 24H 24/0600Z 26.4N 135.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 24/1800Z 27.6N 136.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 25/0600Z 28.4N 136.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 26/0600Z 29.4N 137.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 27/0600Z 30.4N 138.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/0600Z...DISSIPATED $$ Forecaster Roberts
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Tropical Storm Kenneth Forecast Discussion Number 19
2017-08-23 04:37:27| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Tue Aug 22 2017 000 WTPZ43 KNHC 230237 TCDEP3 Tropical Storm Kenneth Discussion Number 19 NWS National Hurricane Center Miami FL EP132017 800 PM PDT Tue Aug 22 2017 Kenneth continues to slowly weaken. The eye feature that was evident several hours ago has filled in, and a recent SSMIS microwave pass shows that the system is now more asymmetric due to southerly shear. A pair of ASCAT passes from around 1800 UTC showed maximum winds in the 55-60 kt range. Assuming some weakening since the time of that data, the initial wind speed is lowered to 55 kt. This estimate is also in agreement with a blend of the latest T- and CI-numbers from TAFB/SAB and ADT values from CIMSS at the University of Wisconsin. Kenneth is over cool 24 deg C waters, surrounded by dry air, and moving toward an environment of even higher southerly wind shear. These hostile conditions should cause the system to keep weakening, and the NHC forecast now calls for Kenneth to become a remnant low in 36 hours. The remnant low will likely only slowly spin down as depicted by the global models. This intensity forecast is largely an update of the previous one. The tropical storm is moving north-northwestward at 10 kt on the west side of a mid-level ridge. This general motion with a decrease in forward speed is expected during the next few days while the system moves into a pronounced weakness in the ridge. By the end of the forecast period, the shallow cyclone is expected to turn to the northwest in the low-level flow. Little change was made to the previous NHC track prediction, and this forecast lies closest to the various consensus models. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 22.6N 134.0W 55 KT 65 MPH 12H 23/1200Z 24.0N 134.7W 50 KT 60 MPH 24H 24/0000Z 25.7N 135.7W 40 KT 45 MPH 36H 24/1200Z 27.0N 136.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 25/0000Z 28.0N 136.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 26/0000Z 29.2N 137.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 27/0000Z 30.2N 138.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/0000Z 31.5N 140.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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Tropical Storm Kenneth Forecast Discussion Number 18
2017-08-22 22:36:55| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Tue Aug 22 2017 000 WTPZ43 KNHC 222036 TCDEP3 Tropical Storm Kenneth Discussion Number 18 NWS National Hurricane Center Miami FL EP132017 200 PM PDT Tue Aug 22 2017 Kenneth's associated deep convection has been diminishing in coverage and intensity. The tropical cyclone is now traversing SSTs below 25 deg C, and continues to weaken. Using a blend of Dvorak T- and CI-numbers from TAFB and SAB gives a current intensity estimate of 60 kt, bringing the system below hurricane strength. Continued weakening at a fairly rapid pace is expected while the system moves over progressively cooler waters and encounters strong shear. The official intensity forecast is close to the latest Florida State University Superensemble prediction, and Kenneth should weaken to a depression and degenerate to a remnant low in 48 hours or sooner. The initial motion estimate remains 330/10 kt. There is no need to make significant changes to the track forecast from the previous advisory package. Kenneth should continue to move through a weakness in the subtropical ridge created by a mid-level trough near 140W longitude. Later in the forecast period, the shallow vortex should turn leftward following the low-level flow. The official track forecast is only slightly to the right of the consensus, and leans toward the GFS and ECMWF tracks. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 21.8N 133.6W 60 KT 70 MPH 12H 23/0600Z 23.1N 134.3W 50 KT 60 MPH 24H 23/1800Z 24.9N 135.3W 40 KT 45 MPH 36H 24/0600Z 26.3N 136.0W 30 KT 35 MPH 48H 24/1800Z 27.5N 136.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 25/1800Z 29.0N 137.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 26/1800Z 30.0N 138.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 27/1800Z 31.0N 140.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch
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