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Tropical Storm KARL Forecast Discussion Number 43
2016-09-25 04:42:54| National Hurricane Center (Atlantic)
Issued at 1100 PM AST SAT SEP 24 2016 000 WTNT42 KNHC 250242 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 43 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 PM AST SAT SEP 24 2016 Karl continues to produce a large area of cold-topped convection to the northeast of the center. However, data from the NOAA P-3, NOAA G-IV, and the NASA/NOAA Global Hawk aircraft indicate that the circulation is losing definition as the cyclone accelerates toward the northeast. The initial intensity of 55 kt is based on a combination of dropsonde, flight level, and SFMR winds from the three planes, and the central pressure of 992 mb is based on data from a Global Hawk dropsonde. While Karl is expected to become post tropical by 24 hours, it should intensify to a hurricane-force system as it does so, and this is shown in the intensity forecast. By 36 hours, the system should be absorbed into a larger extratropical low to its northwest. The initial motion estimate is now 055/25. Karl should continue to accelerate on a general northeastward heading ahead of a broad deep-layer trough until the cyclone is absorbed, and the forward speed is expected to be near 50 kt by 24 hours. The new NHC track forecast is an update of the previous one and remains near the middle of the tightly packed guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 35.0N 58.0W 55 KT 65 MPH 12H 25/1200Z 38.2N 51.3W 60 KT 70 MPH 24H 26/0000Z 44.6N 41.5W 70 KT 80 MPH...POST-TROPICAL 36H 26/1200Z...ABSORBED BY LARGER EXTRATROPICAL LOW $$ Forecaster Beven
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Post-Tropical Cyclone LISA Forecast Discussion Number 22
2016-09-25 04:41:05| National Hurricane Center (Atlantic)
Issued at 1100 PM AST SAT SEP 24 2016 000 WTNT43 KNHC 250240 TCDAT3 POST-TROPICAL CYCLONE LISA DISCUSSION NUMBER 22 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 1100 PM AST SAT SEP 24 2016 No deep convection was observed near the center of Lisa between 1200 UTC yesterday and 0200 UTC today. Although one small areas of convection has tried to develop since then, it is insufficient to meet the organized deep convection requirement for a tropical cyclone. Yesterday's overnight burst of convection seems to have been supported in part by an upper level low, however Lisa has now moved farther to the west of that feature. In the absence of any other synoptic-scale forcing, the redevelopment of widespread deep convection is unlikely. No new scatterometer data is available tonight, so the initial intensity has been held at 30 kt. Without any convection to maintain the circulation, Lisa should gradually spin down over the next day or so before dissipating ahead of a deep-layer trough approaching from the west. The low-level remnants of Lisa are moving around a high pressure system centered near the Azores. The global models are in good agreement that this high will move retreat eastward over the next day or so, which should cause Lisa to turn toward the north in 12-24 hours. A turn toward the north-northeast ahead of the approaching front is possible before the circulation dissipates entirely. FORECAST POSITIONS AND MAX WINDS INIT 25/0300Z 25.8N 40.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 12H 25/1200Z 27.2N 42.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 26/0000Z 29.3N 42.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 26/1200Z 31.4N 42.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 27/0000Z...DISSIPATED $$ Forecaster Beven/Zelinsky
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Tropical Storm KARL Forecast Discussion Number 42
2016-09-24 22:41:36| National Hurricane Center (Atlantic)
Issued at 500 PM AST SAT SEP 24 2016 000 WTNT42 KNHC 242041 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 42 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 PM AST SAT SEP 24 2016 The convective pattern of Karl has become less organized today and currently resembles a shear pattern, which isn't surprising given the 35 kt of southwesterly shear analyzed over Karl by UW-CIMSS. A GPM overpass from earlier today showed that the inner-core structure of the cyclone had degraded, and this was also noted by the last aircraft flight this morning. The initial intensity remains 55 kt based on the latest Dvorak Data-T numbers of T3.5/55 kt from TAFB and SAB. A NOAA Hurricane Hunter aircraft is en route to sample Karl and provide more data on its current intensity and structure. Karl is expected to strengthen during the next 12 to 24 hours, but much of this will be due to baroclinic effects as the cyclone will be under very high shear and moving over cooler SSTs. The NHC forecast shows Karl reaching 70 kt at 24 h as a post-tropical cyclone based on the GFS and ECMWF guidance. Karl should be absorbed by a larger extratropical low over the north Atlantic by 36 h, as indicated by global model fields. The initial motion estimate is 055/20. Karl should continue to accelerate on an east-northeastward to northeastward heading ahead of a broad deep-layer trough until the cyclone is absorbed, and the forward speed is expected to be near 50 kt by 24 hours. The new NHC track forecast is an update of the previous one and remains near the middle of the tightly packed guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 33.6N 61.1W 55 KT 65 MPH 12H 25/0600Z 36.4N 55.3W 60 KT 70 MPH 24H 25/1800Z 41.9N 45.1W 70 KT 80 MPH...POST-TROPICAL 36H 26/0600Z...DISSIPATED $$ Forecaster Brennan
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Tropical Depression LISA Forecast Discussion Number 21
2016-09-24 22:37:38| National Hurricane Center (Atlantic)
Issued at 500 PM AST SAT SEP 24 2016 000 WTNT43 KNHC 242037 TCDAT3 TROPICAL DEPRESSION LISA DISCUSSION NUMBER 21 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 500 PM AST SAT SEP 24 2016 Lisa has been devoid of thunderstorm activity since the convective burst dissipated shortly after 1200 UTC. Assuming some additional spin down since the ASCAT pass this morning, the initial wind speed is lowered to 30 kt, making Lisa a tropical depression again. Meteosat dust product images from the GOES-R Proving Ground indicate that a plume of Saharan dust is approaching Lisa from the east. This dry air combined with westerly shear should cause the depression to degenerate to a remnant low by tonight and continue weakening during the next day or two. The global models are in fair agreement in showing the low opening into a trough in 36 to 48 hours before it gets absorbed by a cold front. Lisa is moving northwestward at 10 kt. A gradual turn to the north is expected during the next day or two while the high pressure system to the north of Lisa shifts eastward. The NHC track forecast is slightly to the left of the previous one, and is in best agreement with the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 25.3N 39.7W 30 KT 35 MPH 12H 25/0600Z 26.4N 41.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 25/1800Z 28.4N 42.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 26/0600Z 30.5N 42.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 26/1800Z...DISSIPATED $$ Forecaster Cangialosi
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Tropical Storm LISA Forecast Discussion Number 20
2016-09-24 16:37:37| National Hurricane Center (Atlantic)
Issued at 1100 AM AST SAT SEP 24 2016 000 WTNT43 KNHC 241437 TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 1100 AM AST SAT SEP 24 2016 The convective burst that occurred overnight has separated from the low-level center of Lisa and is now nearly dissipated. This leaves Lisa as a tight swirl of low-level clouds once again. An ASCAT-B pass around 1200 UTC indicated that maximum winds were close to 40 kt, but given the degradation of the cloud pattern since the pass the initial wind speed is set at 35 kt. This makes Lisa a tropical storm again. Even though Lisa is a little stronger than estimated earlier, the intensity forecast is unchanged from the previous one. Continued strong shear and dry air should cause a gradual decay of the cyclone, and Lisa will likely become a remnant low by tonight. The models are in good agreement in showing the remnant low opening into a trough in 36 to 48 hours before it becomes absorbed by a cold front. Lisa is moving northwestward at 9 kt. A west-northwestward to northwestward motion at about the same speed is expected during the next 24 hours as Lisa remains steered by a high pressure system to its north. A motion more toward the north is forecast to occur on Sunday as the high shifts eastward to near the Azores. Only small adjustments were made to the previous NHC track prediction, and it lies close to a consensus of the GFS and ECMWF models. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 24.7N 38.8W 35 KT 40 MPH 12H 25/0000Z 25.7N 40.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 24H 25/1200Z 27.4N 41.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 26/0000Z 29.3N 42.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 26/1200Z...DISSIPATED $$ Forecaster Cangialosi
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