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| #805659 (Received by flhurricane at: 4:52 PM 05.Oct.2015) TCDAT1 HURRICANE JOAQUIN DISCUSSION NUMBER 33 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 500 PM AST MON OCT 05 2015 Joaquin's cloud pattern has actually improved somewhat since the previous advisory with a cloud-filled eye having briefly appeared in visible satellite imagery. Also, the eye has remained distinct on the Bermuda radar at an altitude above 32,000 feet. Satellite intensity estimates are T4.5/77 kt from SAB, T4.3/72 kt from the NHC AODT technique, and T4.0/65 kt from TAFB. Based on the distinct eye feature noted in visible satellite imagery and radar data, the intensity is being maintained at 75 kt for this advisory. This intensity is also supported by dropsonde data from the NASA WB-57 aircraft, which has been conducting research in Joaquin for the Office of Naval Operation's Tropical Cyclone Intensity experiment. The initial motion estimate is 030/10 kt. Joaquin is rounding the northwestern periphery of a weak ridge located to its southeast, and will be entering the faster mid-latitude westerlies by Tuesday morning. The result should be a gradual turn toward the northeast accompanied by a modest increase in forward speed tonight and Tuesday, followed by more significant acceleration toward the east-northeast at forward speeds of near 30 kt by Wednesday. The official forecast track is a tad to the left of the previous advisory track, and basically lies down the middle of the tightly packed guidance envelope through 36 hours. At 48-120 hours, the extratropical forecast track is based on guidance provided by the NOAA Ocean Prediction Center. The deep-layer vertical wind shear is expected to remain at less than 20 kt for the next 24 hours or so, which should allow for Joaquin to only slightly weaken. By 36 hours and beyond, westerly vertical wind shear is forecast by the global and regional models to increase to more than 30 kt when Joaquin will be moving over sub-24C sea-surface temperatures. The expected result should be steady weakening and a transition to a large and expanding extratropical low pressure system over the much cooler waters of the north Atlantic by 48 hours. However, the GFS and ECMWF models are suggesting that Joaquin could get a baroclinic boost as it interacts with a frontal system and strong jetstream and, as a result, the intensity forecast does not show the typical rapid decay rate of a tropical cyclone moving over 17C-20C SSTs on days 3-5. The NHC intensity forecast is similar to the previous advisory and follows the intensity consensus model IVCN 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 05/2100Z 35.8N 64.0W 75 KT 85 MPH 12H 06/0600Z 37.1N 61.7W 70 KT 80 MPH 24H 06/1800Z 38.7N 57.3W 70 KT 80 MPH 36H 07/0600Z 40.0N 51.0W 65 KT 75 MPH 48H 07/1800Z 41.4N 43.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 72H 08/1800Z 44.0N 28.8W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 09/1800Z 45.6N 20.7W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 10/1800Z 48.0N 14.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
