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Post-Tropical Cyclone HERMINE Forecast Discussion Number 32
2016-09-05 10:57:21| National Hurricane Center (Atlantic)
Issued at 500 AM AST MON SEP 05 2016 000 WTNT44 KNHC 050857 TCDAT4 POST-TROPICAL CYCLONE HERMINE DISCUSSION NUMBER 32 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 500 AM AST MON SEP 05 2016 Hermine remains a post-tropical cyclone with a cloud pattern more reminiscent of an extratropical low. However, moderate convection has been developing just north of the surface center in the northern semicircle during the past few hours within a region of increasing upper-level diffluence. Data from an earlier reconnaissance mission along with recent scatterometer data suggest that the intensity remains unchanged at 60 kt. The initial motion is a slow northward drift 010/03 kt. Water vapor imagery indicates that an upper-level low has developed east of the DelMarVa peninsula and is dropping to the south of Hermine's surface center. The latest model guidance is forecasting the surface and mid- to upper-level lows to rotate counterclockwise around each other for the next 24-36 hours before becoming vertically stacked by 36-48 hours. This cyclonic interaction has resulted in a significant westward shift in the global model tracks, especially by the UKMET and ECMWF models. As a result, the official forecast has been shifted a little to the west of the previous advisory track, but lies along the extreme eastern side of the guidance envelope in the event that the models shift back to the east since such complex interactions are difficult to forecast from cycle to cycle. The upper-level flow across Hermine is forecast by all of the global models to continue to become more difluent during the next 24 hours, which should aid in the development of deep convection near the low-level center. By 36-48 hours, the deep-layer vertical is expected to decrease from the current 45 kt to less than 10 kt, a pattern that is usually conducive for intensification. However, those favorable upper-level conditions will be negated by much cooler sea-surface temperatures of 23-25 deg C when Hermine will be north of the Gulf Stream at that time. The global models are in very agreement on both Hermine weakening and the 34-kt wind field steadily shrinking by 24 hours and beyond. Further weakening is expected through day 4, and both the ECMWF and GFS show Hermine dissipating by day 5 over the cold waters of the North Atlantic. The initial 50-kt wind radii have been adjusted based on data from the reconnaissance aircraft and an earlier ASCAT overpass. FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 37.7N 68.3W 60 KT 70 MPH...POST-TROPICAL 12H 05/1800Z 38.0N 69.1W 60 KT 70 MPH...POST-TROPICAL 24H 06/0600Z 38.6N 70.2W 55 KT 65 MPH...POST-TROPICAL 36H 06/1800Z 39.0N 70.4W 45 KT 50 MPH...POST-TROPICAL 48H 07/0600Z 39.7N 70.1W 40 KT 45 MPH...POST-TROPICAL 72H 08/0600Z 40.7N 67.7W 35 KT 40 MPH...POST-TROPICAL 96H 09/0600Z 43.0N 62.7W 30 KT 35 MPH...POST-TROPICAL 120H 10/0600Z...DISSIPATED $$ Forecaster Stewart
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Post-Tropical Cyclone HERMINE Forecast Discussion Number 31
2016-09-05 04:57:18| National Hurricane Center (Atlantic)
Issued at 1100 PM AST SUN SEP 04 2016 000 WTNT44 KNHC 050257 TCDAT4 POST-TROPICAL CYCLONE HERMINE DISCUSSION NUMBER 31 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1100 PM AST SUN SEP 04 2016 Hermine remains a post-tropical cyclone with all of the deep convection located well north of the center. Deep convection associated with the system has increased over the northern and northwestern portions of the circulation this evening, but it does not appear that there has been an increase in wind speed. The initial intensity is set at 60 kt, which is in agreement with recent SFMR wind observations from an Air Force Reserve reconnaissance aircraft. The aircraft has also recently reported a minimum pressure of 997 mb. Little change in strength is expected overnight, but the global models indicate that weakening should begin by late Monday. Continued weakening is expected during the remainder of the forecast period, and both the ECMWF and GFS dissipate the cyclone by day 5, and this is now reflected in the official forecast. Hermine has continued to move eastward since the previous advisory, but the most recent fix from the aircraft suggests that the eastward motion may be ending. A shortwave trough moving off the coast of North Carolina should cause Hermine to turn northwestward later tonight, then a slow north-northwestward or northward motion should continue into Tuesday. After that time, the cyclone should turn northeastward around the western portion of the mid- to upper-level ridge over the west-central Atlantic. The NHC forecast track is once again a blend of the latest GFS and ECMWF models, but has been adjusted slightly eastward based on the more eastward initial position. The initial wind radii have been adjusted based on data from the reconnaissance aircraft and a recent ASCAT overpass. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 37.2N 68.5W 60 KT 70 MPH...POST-TROPICAL 12H 05/1200Z 37.9N 68.8W 60 KT 70 MPH...POST-TROPICAL 24H 06/0000Z 38.7N 69.7W 55 KT 65 MPH...POST-TROPICAL 36H 06/1200Z 39.2N 70.0W 45 KT 50 MPH...POST-TROPICAL 48H 07/0000Z 39.8N 69.2W 40 KT 45 MPH...POST-TROPICAL 72H 08/0000Z 40.6N 67.2W 35 KT 40 MPH...POST-TROPICAL 96H 09/0000Z 42.5N 63.0W 30 KT 35 MPH...POST-TROPICAL 120H 10/0000Z...DISSIPATED $$ Forecaster Brown
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Tropical Storm NEWTON Forecast Discussion Number 2
2016-09-05 04:53:47| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT SUN SEP 04 2016 000 WTPZ45 KNHC 050253 TCDEP5 TROPICAL STORM NEWTON DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152016 1000 PM CDT SUN SEP 04 2016 A pair of ASCAT passes late this afternoon indicated that the depression was producing 30-35 kt winds on its southern side. Since the last advisory, the circulation and convective pattern have continued to improve, and both subjective and objective Dvorak estimates have increased. Based on all these data, the depression is upgraded to Tropical Storm Newton with maximum winds of 35 kt. There might be multiple low-level swirls rotating around a common center, but the best estimate of the center yields an initial motion of 340/7 kt. Newton is located to the south of a mid-tropospheric ridge which extends from Texas southwestward over the Pacific. However, an amplifying trough near California is expected to shunt the ridge eastward within the next 24 hours, which will help to accelerate Newton toward the northwest or north-northwest during the next couple of days. There is very little spread among the track guidance, but most of the models (with the exception of the EMCWF) are now a little faster than the previous NHC forecast. The new NHC forecast is therefore a little faster, bringing the center of Newton very close to the extreme southern Baja California peninsula in about 36 hours. After that, Newton is forecast to turn northward, moving over the Baja California peninsula, the Gulf of California, and into northwestern mainland Mexico by day 3. Newton is over very deep, warm water at the moment, and SSTs are expected to be between 28-30C until the cyclone reaches the Baja California peninsula. In addition, vertical shear is expected to remain low for the next couple of days. Therefore, Newton is expected to strengthen before it reaches land, with rapid intensification not out of the question. The Rapid Intensification Index currently shows a 1-in-4 chance of a 30-kt increase in winds during the next 24 hours. Most of the hurricane models, both dynamical and statistical, are only showing modest strengthening, but the global model fields indicate that Newton could be near hurricane intensity when it is near the Baja California peninsula. Therefore, the NHC intensity forecast now brings Newton to just below hurricane intensity in 36 hours, which is at the high end of the guidance. Weakening should occur after 36 hours due to interaction with land and increasing vertical shear. Although the official forecast does not explicitly show Newton becoming a hurricane, it will be close enough to hurricane strength that the Government of Mexico has issued a hurricane warning for the extreme southern Baja California peninsula. Additional tropical storm watches and warnings have been issued since Newton's wind field is expected to expand. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 17.0N 105.7W 35 KT 40 MPH 12H 05/1200Z 18.4N 106.7W 40 KT 45 MPH 24H 06/0000Z 20.2N 108.2W 50 KT 60 MPH 36H 06/1200Z 22.3N 109.6W 60 KT 70 MPH 48H 07/0000Z 24.7N 110.8W 55 KT 65 MPH...OVER BAJA PENINSULA 72H 08/0000Z 29.9N 111.3W 35 KT 40 MPH...INLAND 96H 09/0000Z 34.5N 109.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg
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Post-Tropical Cyclone HERMINE Forecast Discussion Number 30
2016-09-04 22:55:16| National Hurricane Center (Atlantic)
Issued at 500 PM AST SUN SEP 04 2016 000 WTNT44 KNHC 042055 TCDAT4 POST-TROPICAL CYCLONE HERMINE DISCUSSION NUMBER 30 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 500 PM AST SUN SEP 04 2016 Satellite images continue to show that practically all of the deep convection continues to occur well to the north and northeast of the low-level center of the cyclone. This indicates that Hermine remains a post-tropical cyclone. The current intensity estimate remains 60 kt based on continuity from the previous aircraft data. Another Air Force reconnaissance plane is scheduled to investigate the system in a few hours. The intensity trends shown by the global models suggest that a weakening trend should begin in 24 hours or so, and this is reflected in the latest official forecast. Visible satellite images show that the center has continued to track farther east than previous estimates, and the motion is a rather uncertain 070/4 kt. A shortwave trough is approaching Hermine from the west, and the associated vorticity is predicted to move just to the south of the post-tropical cyclone within the next day or so. This should cause Hermine to turn toward the north and northwest while moving rather slowly over the next 24-48 hours. After that time, Hermine should begin to move east-northeastward within the southern portion of the mid-latitude westerlies. The official track forecast is a blend of the latest GFS and ECMWF solutions, with the former model much farther east than the latter one. The forecast for Hermine has been coordinated with the NOAA Ocean Prediction Center. Although the NHC forecast track has been shifted eastward today, there is still a threat of tropical storm conditions, coastal flooding and large waves along portions of the mid-Atlantic and northeastern United States coast during the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 37.2N 69.1W 60 KT 70 MPH...POST-TROPICAL 12H 05/0600Z 37.9N 69.2W 60 KT 70 MPH...POST-TROPICAL 24H 05/1800Z 38.5N 70.0W 60 KT 70 MPH...POST-TROPICAL 36H 06/0600Z 39.1N 70.5W 55 KT 65 MPH...POST-TROPICAL 48H 06/1800Z 39.6N 70.5W 45 KT 50 MPH...POST-TROPICAL 72H 07/1800Z 40.2N 69.2W 45 KT 50 MPH...POST-TROPICAL 96H 08/1800Z 41.5N 65.5W 40 KT 45 MPH...POST-TROPICAL 120H 09/1800Z 43.5N 61.0W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Pasch
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Tropical Depression FIFTEEN-E Forecast Discussion Number 1
2016-09-04 22:50:45| National Hurricane Center (East Pacific)
Issued at 400 PM CDT SUN SEP 04 2016 000 WTPZ45 KNHC 042050 TCDEP5 TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152016 400 PM CDT SUN SEP 04 2016 The area of low pressure located near the southwestern coast of Mexico has become better organized today. Satellite data indicate that the center of circulation is now well defined, and thunderstorm activity is sufficiently organized to classify the system as a tropical depression. A recent ASCAT pass indicated that maximum winds were near 30 kt, and that is used as the initial wind speed. The initial motion of the depression is highly uncertain since it has just formed, but the best guess is 345/2 kt. A faster northwestward motion is expected to begin tonight and continue for the next couple of days while the system moves in the flow on the southwestern edge of a mid-level ridge. This pattern should take the cyclone very near or over the southern portion of the Baja California peninsula in about 2 days. A more northward motion is forecast after that time when the cyclone moves around the ridge. The model guidance is in fair agreement on this scenario, and the NHC track forecast lies close to the middle of the guidance envelope. The depression is in an environment of moist air, moderate shear and over warm waters. Since the cyclone is expected to remain in those conditions until it nears the Baja coast, steady strengthening is anticipated. Once it crosses Baja, land interaction and an increase in shear should cause weakening. The NHC intensity forecast is fairly close to the intensity model consensus. It is worth noting that there are large differences in the future wind radii predicted by the global and statistical models. The NHC size forecast closely follows the wind radii consensus model. Based on the current forecast, the government of Mexico has issued a Hurricane Watch for the southern portion of the Baja California peninsula. A tropical storm or hurricane warning could be required by tonight. Heavy rains, which could result in flash flooding and mud slides, are expected to continue over portions of southwestern Mexico for another day or so. These rains will likely spread over the Baja California peninsula within the next couple of days. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 16.0N 105.4W 30 KT 35 MPH 12H 05/0600Z 17.1N 106.0W 40 KT 45 MPH 24H 05/1800Z 18.6N 107.4W 45 KT 50 MPH 36H 06/0600Z 20.7N 109.0W 50 KT 60 MPH 48H 06/1800Z 22.8N 110.5W 55 KT 65 MPH 72H 07/1800Z 28.0N 112.2W 40 KT 45 MPH 96H 08/1800Z 32.3N 111.1W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi
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