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Hurricane JOAQUIN Forecast Discussion Number 39

2015-10-07 10:33:05| National Hurricane Center (Atlantic)

Issued at 500 AM AST WED OCT 07 2015 000 WTNT41 KNHC 070832 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 39 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 AM AST WED OCT 07 2015 The organization of Joaquin continues to slowly decrease, with the central convection now present only in the northeastern semicircle. Satellite intensity estimates from TAFB and SAB are now 65 kt, and that is the advisory intensity. Joaquin is now moving over colder water north of the Gulf Stream, and the cyclone is gradually becoming embedded in a baroclinic zone. This combination should cause continued weakening and eventual extratropical transition. The current expectation is that the central convection will dissipate before the cyclone develops fronts, so the intensity forecast calls for Joaquin to become post-tropical for about 12 hours before becoming extratropical. The new intensity forecast shows a slightly faster weakening than the previous forecast, and calls for Joaquin or its remnants to dissipate by 120 hours. Joaquin continues moving rapidly east-northeastward as it is embedded in strong westerly flow north of the subtropical ridge. This motion should continued for another 36 hours or so. After that time, the guidance is now in better agreement that the cyclone should turn decelerate and turn east-southeastward as it comes under the influence of a developing deep-layer trough over western Europe. The new forecast track is an update of the previous track. The track, intensity, and wind radii forecasts for 24 hours and beyond are based upon guidance provided by the Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 40.5N 49.4W 65 KT 75 MPH 12H 07/1800Z 41.4N 43.5W 60 KT 70 MPH 24H 08/0600Z 42.4N 35.5W 55 KT 65 MPH...POST-TROPICAL 36H 08/1800Z 43.3N 28.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 48H 09/0600Z 44.2N 23.2W 45 KT 50 MPH...POST-TROP/EXTRATROP 72H 10/0600Z 44.0N 16.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 11/0600Z 43.0N 12.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 12/0600Z...DISSIPATED $$ Forecaster Beven

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Hurricane JOAQUIN Forecast Discussion Number 38

2015-10-07 04:56:01| National Hurricane Center (Atlantic)

Issued at 1100 PM AST TUE OCT 06 2015 000 WTNT41 KNHC 070255 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM AST TUE OCT 06 2015 Until just a couple of hours ago, Joaquin continued to display a tight inner core, with deep convection surrounding a 20 n mi diameter eye. The most recent geostationary infrared imagery is finally showing that the convection is becoming asymmetric with the 25 kt of tropospheric vertical shear adversely affecting the cyclone. The intensity remains 70 kt, since both the SAB and TAFB Dvorak Current Intensity values are unchanged. The hurricane is about to cross over the north wall of the Gulf Stream and will be traversing very chilly 21-22C waters by tomorrow. The combination of cold SSTs, dry air, and strong vertical shear should cause the deep convection to either completely dislocate or cease and the forecast calls for Joaquin to become a strong post-tropical cyclone in about a day. The FSU Cyclone Phase Space diagrams, based upon the global and regional models, suggest that Joaquin will gradually become more frontal and extratropical transition is anticipated by Thursday. Baroclinic forcing should allow for only a gradual winding down as depicted by the models, and dissipation is anticipated in about five days. Joaquin is moving toward the east-northeast at a rather quick pace of 25 kt, as it is being advected along by the mid-latitude westerlies. The system should accelerate east-northeastward for about 36 hours, before slowing down in the eastern north Atlantic. The track forecast is based upon the tightly clustered global and regional models through 72 hours. By day four, the guidance becomes divergent with some solutions turning northeastward toward Ireland and Great Britain, but most turning east-southeastward toward Portugal and Spain. This latter scenario is the basis for the track forecast at day 4. The track, intensity, and wind radii forecasts from 36 hours and beyond are based upon guidance provided by the Ocean Prediction Center. A last-minute-arriving ASCAT scatterometer pass indicated that Joaquin continues to expand in size. The 34- and 50-kt wind radii analyses and forecasts were adjusted accordingly. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 40.0N 53.1W 70 KT 80 MPH 12H 07/1200Z 41.0N 47.7W 65 KT 75 MPH 24H 08/0000Z 42.1N 39.3W 60 KT 70 MPH...POST-TROPICAL 36H 08/1200Z 43.4N 31.2W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 09/0000Z 44.7N 25.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 10/0000Z 44.0N 17.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 11/0000Z 43.0N 13.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 12/0000Z...POST-TROP/EXTRATROP $$ Forecaster Landsea

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Hurricane JOAQUIN Forecast Discussion Number 37

2015-10-06 23:37:03| National Hurricane Center (Atlantic)

Issued at 500 PM AST TUE OCT 06 2015 000 WTNT41 KNHC 062136 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 37...CORRECTED NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 PM AST TUE OCT 06 2015 CORRECTED FORWARD SPEED TO 20 KT IN SECOND PARAGRAPH Joaquin continues to have a very impressive cloud pattern with an intermittent eye on visible images. In fact, microwave data still shows a distinct eye feature surrounded by convective bands. Dvorak T-numbers have not changed today, and given the currently well- organized cloud pattern, the initial intensity is kept at 70 kt. Both cold sea surface temperatures and strong shear should cause Joaquin to begin losing tropical characteristics between 24 and 36 hours, and after that time, the hurricane is forecast to become a strong extratropical cyclone. Joaquin is fully embedded within the mid-latitude westerlies and is racing toward the east-northeast at about 20 kt. Track guidance is tightly packed, showing Joaquin moving on the same general track for the next few days with some increase in forward speed. However, Joaquin should decrease in forward speed by the end of the forecast period. The NHC forecast is basically on top of the multi-model consensus, and very near the consensus of the ECMWF and the GFS. FORECAST POSITIONS AND MAX WINDS INIT 06/2100Z 39.0N 56.9W 70 KT 80 MPH 12H 07/0600Z 40.4N 51.6W 65 KT 75 MPH 24H 07/1800Z 42.0N 44.0W 60 KT 70 MPH 36H 08/0600Z 43.0N 36.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 08/1800Z 44.0N 28.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 09/1800Z 46.5N 20.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 10/1800Z 48.0N 13.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/1800Z 49.0N 10.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Avila

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Hurricane JOAQUIN Forecast Discussion Number 36

2015-10-06 16:43:26| National Hurricane Center (Atlantic)

Issued at 1100 AM AST TUE OCT 06 2015 000 WTNT41 KNHC 061443 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 36 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 AM AST TUE OCT 06 2015 Joaquin is in a state of gradual decay. Although an eye feature is still occasionally visible, there has been some erosion of the inner-core deep convection. A series of microwaves images this morning indicate some eastward tilt of the vortex with height, and there is evidence of dry air entrainment into the inner core. Dvorak intensity estimates are slowly decreasing, and the initial wind speed is reduced to 70 kt. An increase in southwesterly shear and cooler waters along Joaquin's track should cause further weakening during the next few days. Cooler and drier air behind a low-level baroclinic zone currently draped to the north of the cyclone should gradually be advected into Joaquin's circulation during the next 24 to 48 hours, and extratropical transition is expected to be complete in about 36 hours. The new intensity forecast is near the multi-model consensus through 36 hours and then a bit above that after that time. Recent fixes indicate that Joaquin has is accelerating northeastward, and the initial motion estimate is 055/16. The cyclone is expected to further accelerate toward the east-northeast as it becomes fully embedded in a belt of nearly zonal middle- to upper-tropospheric flow during the next few days. After extratropical transition, Joaquin should experience a significant deceleration when it approaches the British Isles. The track guidance is tightly clustered through 48 hours, with somewhat greater spread after that time. The new track forecast is about the same as the previous one and lies near the multi-model consensus for the remainder of the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 06/1500Z 38.3N 59.6W 70 KT 80 MPH 12H 07/0000Z 39.5N 55.1W 65 KT 75 MPH 24H 07/1200Z 40.8N 48.0W 60 KT 70 MPH 36H 08/0000Z 42.0N 40.2W 55 KT 65 MPH 48H 08/1200Z 43.3N 32.3W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 09/1200Z 46.2N 21.2W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 10/1200Z 49.3N 14.9W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 11/1200Z 49.8N 10.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Kimberlain

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Hurricane JOAQUIN Forecast Discussion Number 34

2015-10-06 04:52:32| National Hurricane Center (Atlantic)

Issued at 1100 PM AST MON OCT 05 2015 000 WTNT41 KNHC 060252 TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 34 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM AST MON OCT 05 2015 While Joaquin's eye is no longer present in the shortwave infrared imagery from the GOES-East geostationary satellite this evening, a distinct eye has been visible in the microwave imagery from the SSMIS polar orbiting satellite passes at 2231Z and 2316Z. There is even a suggestion of a concentric eyewall at about a 50 nm radius. Dvorak Current Intensity numbers from SAB and TAFB remain at 4.5, supporting continuing with an intensity of 75 kt. The wind radii were expanded slightly based upon a CIRA AMSU wind radii analysis from 2104Z. Joaquin is currently embedded in moderate southwesterly vertical shear with somewhat dry mid-tropospheric air, and is traversing over SSTs near 27C. During the next day, the shear picks up substantially. However, with Joaquin moving in the same direction as the shear vector, the negative impact of the shear is lessened as indicated in the SHIPS output. Within two days, Joaquin will move north of the Gulf Stream and will encounter very cold waters while the shear increases even more. This would typically lead toward a quick decay of a tropical cyclone, but Joaquin is expected to transform into an extratropical cyclone in about 48 hours. The baroclinic processes should allow Joaquin instead to slowly decay. The intensity forecast is based upon the tightly clustered IVCN multi-model consensus through 36 hours, and then is based on guidance provided by the Ocean Prediction Center for the 48-120 hour period. The initial motion of Joaquin is 35 deg/12 kt, fairly confidently known because of the microwave fixes. Joaquin is being swept up in the mid-latitude westerlies and should begin accelerating off toward the east-northeast during the next two to three days. The track prediction is based upon the tightly clustered TVCN multi-model consensus through 36 hours, and then is based on guidance provided by the Ocean Prediction Center for the 48-120 hour period. FORECAST POSITIONS AND MAX WINDS INIT 06/0300Z 36.8N 62.7W 75 KT 85 MPH 12H 06/1200Z 38.1N 59.9W 75 KT 85 MPH 24H 07/0000Z 39.6N 54.5W 70 KT 80 MPH 36H 07/1200Z 41.0N 47.2W 65 KT 75 MPH 48H 08/0000Z 42.0N 38.8W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 09/0000Z 45.0N 23.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 10/0000Z 46.0N 17.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 11/0000Z 48.0N 12.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Landsea

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