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Tropical Storm JULIA Forecast Discussion Number 9
2016-09-16 04:33:00| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT THU SEP 15 2016 000 WTNT41 KNHC 160232 TCDAT1 TROPICAL STORM JULIA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 1100 PM EDT THU SEP 15 2016 Just like it occurred last night, a surge of strong upper-level westerly winds removed the convection from the center of Julia again tonight. Satellite images show that the circulation is still vigorous, and it is generously assumed that tropical-storm-force winds are occuring well to the east of the center. On this basis, the initial intensity is kept at 35 kt. The strong shear is forecast to persist, and the most likely solution is for Julia to maintain the same intensity for another 12 hours or so, and then gradually decay as indicated in the previous NHC forecast. It is worth noting that the SHIPS and LGEM models maintain Julia as tropical storm for the next 3 days, but the given the strong shear predicted by these models, their solution does not appear to be realistic. The tight swirl of low clouds defining the center of Julia has been moving slowly toward the east-southeast or 120 degrees at 4 kt. However, the steering currents are expected to be weak, and the NHC forecast calls for Julia to meander during the next 2 to 3 days. By then, Julia is expected to be a remnant low, and probably will begin to drift northeastward, embedded within the mid-latitude flow. Since the steering currents are likely to be weak and poorly defined, the track models are showing divergent solutions, varying from northeast to southwest tracks, and some show no motion at all. The discrepancy in the models increases the uncertainty of the NHC track forecast. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 31.5N 77.1W 35 KT 40 MPH 12H 16/1200Z 31.2N 76.7W 35 KT 40 MPH 24H 17/0000Z 31.0N 76.5W 30 KT 35 MPH 36H 17/1200Z 31.5N 76.5W 30 KT 35 MPH 48H 18/0000Z 31.5N 76.5W 30 KT 35 MPH 72H 19/0000Z 31.5N 76.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 20/0000Z 32.5N 75.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 21/0000Z...DISSIPATED $$ Forecaster Avila
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Tropical Storm JULIA Forecast Discussion Number 8
2016-09-15 22:50:31| National Hurricane Center (Atlantic)
Issued at 500 PM EDT THU SEP 15 2016 000 WTNT41 KNHC 152050 TCDAT1 TROPICAL STORM JULIA DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 500 PM EDT THU SEP 15 2016 An Air Force Reserve Hurricane Hunter aircraft investigated Julia and reported estimated surface winds of 35-40 kt from the SFMR instrument in the northeast quadrant, along with a central pressure of 1007 mb. The maximum flight-level winds at 850 mb were 34 kt. Based on a blend of the surface estimates and flight-level winds, the initial intensity is increased to 35 kt. The aircraft reported a sharp trough extending to the east of the center, and the storm is producing vigorous convective bursts near the center and along the trough. Julia continues to move generally eastward or 085/7, possibly due to the reformation of the center caused by the convective bursts. The track guidance continues to forecast that the cyclone will slow its forward motion in the next 12 hours, after which it will move very little through 72-96 hours. Based on this premise, which so far has not come to pass, the new forecast track will keep Julia moving east for 12 hours and then show a loop from 12-96 hours. The new forecast area of meandering is about 60 n mi east of that from the previous forecast. Julia is likely to experience very strong westerly to northwesterly shear from 12-84 hours, and this is expected to cause a gradual weakening during this time. The NHC intensity forecast follows the previous one in calling for the cyclone to degenerate to a remnant low by 72 hours and dissipate completely by 120 hours. If Julia survives the extended period of shear, the environment should become more favorable after 84 hours, and the system could re-intensify as forecast by the UKMET and Canadian models. FORECAST POSITIONS AND MAX WINDS INIT 15/2100Z 32.1N 77.1W 35 KT 40 MPH 12H 16/0600Z 32.0N 76.6W 35 KT 40 MPH 24H 16/1800Z 31.8N 76.4W 30 KT 35 MPH 36H 17/0600Z 31.5N 76.4W 30 KT 35 MPH 48H 17/1800Z 31.5N 76.7W 30 KT 35 MPH 72H 18/1800Z 32.0N 77.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/1800Z 32.5N 76.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/1800Z...DISSIPATED $$ Forecaster Beven
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Tropical Storm IAN Forecast Discussion Number 14
2016-09-15 22:43:58| National Hurricane Center (Atlantic)
Issued at 500 PM AST THU SEP 15 2016 000 WTNT45 KNHC 152043 TCDAT5 TROPICAL STORM IAN DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016 500 PM AST THU SEP 15 2016 A scatterometer overpass shows that the circulation of Ian is losing definition as the cyclone accelerates northeastward, with the system elongating north to south. The scatterometer did not sample the maximum winds, and the subtropical cyclone satellite intensity estimates are unchanged. Based on this, the initial intensity remains a likely conservative 45 kt. Ian is forecast to merge with a baroclinic zone and undergo extratropical transition during the next 12-36 hours, and in the process it is expected to strengthen to at least storm-force before it is absorbed by another extratropical low. The new intensity forecast is an update of the previous forecast based on the global models and guidance from the Ocean Prediction Center. Ian continues to accelerate northeastward and the initial motion is now 040/30 kt. A northeastward motion with an additional increase in forward speed is expected before the cyclone is absorbed. The new forecast track remains near the center of the tightly clustered track guidance. FORECAST POSITIONS AND MAX WINDS INIT 15/2100Z 39.6N 47.7W 45 KT 50 MPH 12H 16/0600Z 43.2N 42.7W 55 KT 65 MPH...POST-TROPICAL 24H 16/1800Z 49.5N 34.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 17/0600Z 55.5N 26.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 17/1800Z 61.0W 18.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 18/1800Z...ABSORBED BY EXTRATROPICAL LOW $$ Forecaster Beven
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Tropical Depression JULIA Forecast Discussion Number 7
2016-09-15 16:48:30| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT THU SEP 15 2016 000 WTNT41 KNHC 151448 TCDAT1 TROPICAL DEPRESSION JULIA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112016 1100 AM EDT THU SEP 15 2016 New convection has formed near and east of the center of Julia during the past few hours, although the low-level center remains partially exposed due to westerly vertical wind shear. Subjective satellite intensity estimates from SAB and TAFB are 30 and 35 kt respectively, while various objective estimates are 35-45 kt. The initial intensity is kept at 30 kt pending the arrival of an Air Force Reserve Hurricane Hunter aircraft, but there is a possibility that this is conservative. After not moving much overnight, the center of Julia has jumped eastward this morning. The overall long-term motion is 095/7, but the short-term motion is significantly faster than that. The forecast guidance is in good agreement that Julia should move little after 12 hours, and the new track forecast is based on the premise that the current forward speed will decrease by the 12 hours point. The new forecast track has the same general idea as the previous track, but the area where Julia will meander is now forecast to be about 90 n mi farther east than in the previous forecast. Julia is forecast to experience very strong westerly to northwesterly shear for the next four days or so, and this is expected to cause a gradual weakening during this time. The NHC intensity forecast follows the previous one, as well as the GFS and ECMWF models, in calling for the cyclone to degenerate to a remnant low by 72 hours and dissipate completely by 120 hours. It should be noted that the shear could decrease after 96 hours, and the UKMET and Canadian models forecast re-intensification at that time. However, at this time it appears unlikely that the cyclone will survive long enough to take advantage of the possibly more favorable environment. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 31.8N 78.2W 30 KT 35 MPH 12H 16/0000Z 31.8N 78.0W 30 KT 35 MPH 24H 16/1200Z 31.7N 77.7W 30 KT 35 MPH 36H 17/0000Z 31.6N 77.5W 30 KT 35 MPH 48H 17/1200Z 31.4N 77.5W 30 KT 35 MPH 72H 18/1200Z 31.5N 77.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 19/1200Z 32.0N 77.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/1200Z...DISSIPATED $$ Forecaster Beven
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Tropical Storm IAN Forecast Discussion Number 13
2016-09-15 16:43:01| National Hurricane Center (Atlantic)
Issued at 1100 AM AST THU SEP 15 2016 000 WTNT45 KNHC 151442 TCDAT5 TROPICAL STORM IAN DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016 1100 AM AST THU SEP 15 2016 After looking more like a subtropical cyclone than a tropical cyclone for most of the past 24 hours, there has recently been an increase in convective banding over the eastern semicircle of Ian. The initial intensity remains 45 kt based on a subtropical cyclone intensity estimate from TAFB. Ian is forecast to merge with the westerlies and undergo extratropical transition during the next 36-48 hours, and in the process it is expected to strengthen to at least storm-force before it is absorbed by another extratropical low. The new intensity forecast is an update of the previous forecast based on the global models and guidance from the Ocean Prediction Center Ian is accelerating northeastward and the initial motion is now 040/21. A northeastward motion with an additional increase in forward speed is expected before the cyclone is absorbed. The new forecast track is near the center of the tightly clustered track guidance. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 37.2N 50.5W 45 KT 50 MPH 12H 16/0000Z 40.3N 46.8W 55 KT 65 MPH 24H 16/1200Z 45.6N 39.6W 60 KT 70 MPH...POST-TROPICAL 36H 17/0000Z 51.5N 32.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 17/1200Z...MERGED WITH EXTRATROPICAL LOW $$ Forecaster Beven
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