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Tropical Storm KARL Forecast Discussion Number 35

2016-09-23 04:51:29| National Hurricane Center (Atlantic)

Issued at 1100 PM AST THU SEP 22 2016 000 WTNT42 KNHC 230251 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 35 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 1100 PM AST THU SEP 22 2016 Reports from Air Force Reserve and NOAA Hurricane Hunter aircraft indicate that Karl has become significantly better organized during the past 24 hours, with dropsonde data showing that a well-defined circulation now exists from the surface to 400 mb. The maximum flight-level winds were 56 kt at 8000 ft, and there were numerous SFMR surface wind estimates of 35-40 kt. The minimum central pressure estimated from the aircraft data is 1001 mb based on a 1003 mb dropsonde with surface winds of 24 kt. Based on these data and observations from NOAA buoy 41049, the initial intensity is now 40 kt. Additional aircraft data should be available starting at about 0600 UTC. The initial motion is now 315/14 as Karl continues moving northwestward between the subtropical ridge and a mid- to upper-level trough north of Hispaniola and east of the Bahamas. During the next 24-36 hours, Karl should turn northward and then northeastward as it moves through a break in the ridge into the westerlies. Subsequently, the cyclone should accelerate northeastward. The model guidance is in excellent agreement with this scenario, although there remains some spread in the forecast forward speed late in the forecast period between the slower ECMWF and the other faster models. The new forecast track remains down the center of the guidance and overall is similar to the previous track. The new forecast track is shifted a little closer to Bermuda, with the closest approach now forecast between 24 and 36 hours. While there remain some differences in the model details, Karl is expected to move into an area of decreasing vertical shear during the next 48 hours, which should allow continued development. After that, the cyclone should begin extratropical transition, which is likely to be complete by 72 hours according the the latest dynamical model guidance. The new intensity forecast is similar to the previous forecast and calls for Karl to steadily intensify to hurricane strength in about 48 hours, followed by rapid weakening after extratropical transition. The forecast also follows the dynamical models in calling for Karl to be absorbed by another extratropical low by 120 hours. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 27.0N 64.0W 40 KT 45 MPH 12H 23/1200Z 28.4N 65.0W 45 KT 50 MPH 24H 24/0000Z 30.5N 64.8W 50 KT 60 MPH 36H 24/1200Z 32.4N 62.6W 60 KT 70 MPH 48H 25/0000Z 35.2N 57.4W 70 KT 80 MPH 72H 26/0000Z 43.5N 41.0W 70 KT 80 MPH...POST-TROP/EXTRATROP 96H 27/0000Z 53.0N 26.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 28/0000Z...ABSORBED BY EXTRATROPICAL LOW $$ Forecaster Beven

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Tropical Storm LISA Forecast Discussion Number 14

2016-09-23 04:38:56| National Hurricane Center (Atlantic)

Issued at 1100 PM AST THU SEP 22 2016 000 WTNT43 KNHC 230238 TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL132016 1100 PM AST THU SEP 22 2016 Lisa continues to struggle in the face of strong deep-layer shear. Although the cyclone continues to pulsate convection, several microwave passes between 1900 and 2100 UTC indicate that the center has become somewhat more removed from the deepest convection since this afternoon. The initial intensity has been lowered to 40 kt, in line with decreased Dvorak estimates from TAFB and SAB. A 2344 UTC ASCAT-B pass missed the center of Lisa, but showed that 35 kt winds are present 100-150 nm NE of the presumed center. Lisa is forecast to remain in a high shear and increasingly dry environment, so further weakening seems inevitable. The main question is how quickly will the deep convection cease to exist. The GFS and HWRF both show mid- to upper-level dry air cutting over the circulation in about 36 to 48 hours, suggesting a complete lack of deep convection in those models at that time. The official forecast now calls for Lisa to become post tropical within 48 hours, before being absorbed by an approaching front after 96 hours. There is little change to the track forecast reasoning overall. Lisa continues to move toward the northwest, or 320 degrees, at a rather uncertain 8 kt. A lack of microwave or scatterometer data over the center since 2100 UTC has made the center difficult to locate and introduces some uncertainty to the forecast. Regardless, Lisa should continue moving northwestward around a low- to mid-level ridge, located east of the Azores, before recurving ahead of an approaching front. The first 48 hours of the forecast are near a consensus of the GFS and ECMWF models. The 72 and 96 hour points incorporate guidance from the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 21.3N 35.2W 40 KT 45 MPH 12H 23/1200Z 22.4N 36.3W 35 KT 40 MPH 24H 24/0000Z 23.6N 37.8W 30 KT 35 MPH 36H 24/1200Z 24.7N 39.3W 30 KT 35 MPH 48H 25/0000Z 26.2N 40.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 26/0000Z 30.5N 41.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 27/0000Z 35.5N 37.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 28/0000Z...ABSORBED $$ Forecaster Beven/Zelinsky

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Tropical Storm KARL Forecast Discussion Number 34

2016-09-22 22:51:48| National Hurricane Center (Atlantic)

Issued at 500 PM AST THU SEP 22 2016 000 WTNT42 KNHC 222051 TCDAT2 TROPICAL STORM KARL DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 500 PM AST THU SEP 22 2016 Air Force Reserve and NOAA Hurricane Hunter aircraft have been flying in Karl, and the data indicate that the cyclone has re-intensified to a 35-kt tropical storm. The maximum 850-mb flight-level wind so far is 45 kt, which equates to an intensity of about 35 kt. This is also supported by SFMR observations. In addition, dropsonde data suggest lowering the central pressure down to 1005 mb. Combined with the aircraft data, scatterometer winds within the convective bands indicate that tropical-storm-force winds extend 120 nm to the north of the center of circulation. Karl has continued its northwestward progression at 305 degrees with a speed of 14 knots. The synoptic pattern around this system features a mid-level high off to its northeast while a mid-level low is positioned to the north of Puerto Rico. Karl is forecast to move around the western extent of the anticyclone which will make it turn more northward by 36 hours before accelerating northeastward into the mid-latitude westerlies by 48 hours. Based on the adjustment of the initial position provided by the aircraft, the track guidance has shifted a bit left of the positions indicated in the previous advisory. As a result, the updated official forecast has been adjusted westward during the first 48 hours, lying a bit closer to the GFS/GEFS mean clustering while giving some credit to the TVCN multi-model consensus. Later in the period, the ECMWF solution was deemed too slow and was not weighted as heavily at that point. Karl lies right along the edge of a zone of higher shear to its west, and the various analyses are showing about 15 to 20 knots of southeasterly shear over the system. The global models continue to show the shear decreasing at least some during the next couple of days, but there are differences. For example, GFS fields show the shear decreasing to around 5 knots or less by Friday morning through evening, while the ECMWF only shows the shear decreasing to around 10 knots during the same period. This continues to make the intensity forecast difficult. At this point, the intensity forecast was generally left unchanged which allows Karl to become a Category 1 hurricane by Sunday. Based on the latest forecast, the western edge of the tropical-storm-force wind field could begin to affect Bermuda during the next 24 to 36 hours. The Bermuda Weather Service has therefore issued a Tropical Storm Warning for the island. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 25.5N 63.2W 35 KT 40 MPH 12H 23/0600Z 26.8N 64.4W 40 KT 45 MPH 24H 23/1800Z 28.8N 65.1W 45 KT 50 MPH 36H 24/0600Z 30.8N 64.2W 50 KT 60 MPH 48H 24/1800Z 32.7N 61.0W 60 KT 70 MPH 72H 25/1800Z 39.7N 47.0W 70 KT 80 MPH 96H 26/1800Z 49.0N 29.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 27/1800Z...DISSIPATED $$ Forecaster Campbell/Rubin-Oster/Berg

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Tropical Depression KARL Forecast Discussion Number 33

2016-09-22 16:49:15| National Hurricane Center (Atlantic)

Issued at 1100 AM AST THU SEP 22 2016 000 WTNT42 KNHC 221449 TCDAT2 TROPICAL DEPRESSION KARL DISCUSSION NUMBER 33 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 ISSUED BY THE NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1100 AM AST THU SEP 22 2016 Even with visible satellite imagery this morning, Karl's center has still been difficult to locate, and it's unclear exactly how well defined it is. Deep convection has increased markedly since yesterday, but the overall cloud pattern is rather elongated from the east-southeast to the west-northwest. In the absence of any in situ data, the initial intensity remains 30 kt based on Dvorak estimates from TAFB and SAB. Karl is moving northwestward and appears to have sped up temporarily with an initial motion of 305/15 kt. The cyclone is moving between a mid-level high centered to its northeast and a mid-level low located north of Puerto Rico. Karl is expected to move around the western periphery of the high during the next few days, turning northward by 36 hours and then accelerating northeastward into the mid-latitude westerlies by 48 hours. Based on the adjustment of the initial position, the track guidance has shifted a bit left of the positions indicated in the previous advisory. As a result, the updated official forecast has been adjusted westward during the first 48 hours, lying close to the ECMWF solution as well as the TVCN multi-model consensus. Even with this shift, the official forecast lies close to the eastern edge of the guidance envelope. Karl lies right along the edge of a zone of higher shear to its west, and the various analyses are showing about 15 kt of southeasterly shear over the system. The global models continue to show the shear decreasing at least some during the next couple of days, but there are differences. For example, GFS fields show the shear decreasing below 10 kt for a day or two, while the ECMWF only shows the shear decreasing below 10 kt for about 12 hours. This continues to make the intensity forecast difficult. For now, the official intensity forecast remains close to the ICON intensity consensus, and no significant changes were made to the previous forecast. Based on the latest forecast, the western edge of the tropical-storm-force wind field could begin to affect Bermuda during the next 36 to 48 hours. The Bermuda Weather Service has therefore issued a Tropical Storm Watch for the island. FORECAST POSITIONS AND MAX WINDS INIT 22/1500Z 25.0N 62.3W 30 KT 35 MPH 12H 23/0000Z 26.3N 63.7W 35 KT 40 MPH 24H 23/1200Z 28.3N 64.8W 40 KT 45 MPH 36H 24/0000Z 30.2N 64.7W 45 KT 50 MPH 48H 24/1200Z 32.3N 62.5W 55 KT 65 MPH 72H 25/1200Z 38.0N 50.8W 70 KT 80 MPH 96H 26/1200Z 48.0N 32.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 27/1200Z...DISSIPATED $$ Forecaster Berg/Campbell/Rubin-Oster

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Tropical Depression KARL Forecast Discussion Number 32

2016-09-22 10:42:53| National Hurricane Center (Atlantic)

Issued at 500 AM AST THU SEP 22 2016 000 WTNT42 KNHC 220842 TCDAT2 TROPICAL DEPRESSION KARL DISCUSSION NUMBER 32 NWS NATIONAL HURRICANE CENTER MIAMI FL AL122016 500 AM AST THU SEP 22 2016 Although Karl's cloud pattern is better organized than 24 hours ago, the cyclone lacks an inner core, and there is no new data or intensity estimates suggesting that the winds have increased. Thus, the initial intensity remains 30 kt. Karl is heading toward even warmer waters, and the shear is expected to be light for the next day or two. These conditions should favor some slight strengthening during that period. Model guidance suggests that additional intensification will likely occur after Karl's recurvature in a couple of days. This is reflected in the NHC forecast which bring Karl to hurricane status as it moves northeastward over the open Atlantic, and before it becomes extratropical. Karl continues to move toward the northwest or 315 degrees at 14 kt. The cyclone is about to reach the southwestern edge of the subtropical ridge, and this pattern should force Karl to turn northward in about a day or so. Thereafter, the cyclone is expected to turn sharply toward the northeast while it becomes embedded within the southwesterly flow associated with an amplifying mid-latitude trough. The NHC track forecast follows very closely the multimodel consensus, and is in the middle of the guidance envelope, which in fact is tightly packed at least for the next 3 days. Although Karl is expected to recurve over the open Atlantic southeast of Bermuda, interests in that island should monitor the progress of Karl. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 24.0N 60.7W 30 KT 35 MPH 12H 22/1800Z 25.3N 62.2W 35 KT 40 MPH 24H 23/0600Z 27.0N 63.8W 40 KT 45 MPH 36H 23/1800Z 29.3N 64.1W 45 KT 50 MPH 48H 24/0600Z 31.5N 63.0W 55 KT 65 MPH 72H 25/0600Z 36.5N 54.0W 70 KT 80 MPH 96H 26/0600Z 47.0N 34.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 27/0600Z...ABSORBED BY A LARGE EXTRATROPICAL LOW $$ Forecaster Avila

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