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Tropical Storm Julian Forecast Discussion Number 4
2021-08-29 22:39:43| National Hurricane Center (Atlantic)
Issued at 900 PM GMT Sun Aug 29 2021 000 WTNT41 KNHC 292039 TCDAT1 Tropical Storm Julian Discussion Number 4 NWS National Hurricane Center Miami FL AL112021 900 PM GMT Sun Aug 29 2021 The convective pattern and structure of Julian has remained consistent throughout today, with the low-level center remaining tucked under the southwestern edge of a deep convective mass and good outflow in the northeastern semicircle. A late morning ASCAT-C overpass sampled peak winds of 45 to 47 kt, and since the cyclone has likely intensified slightly since that time, the initial intensity has been increased to 50 kt. Julian is now moving quickly to the northeast, or 050/21 kt in southwesterly flow to the south of a deep-layer area of low pressure located just east of Newfoundland. The storm is forecast to continue to move northeastward at a similar forward speed through Monday, and then begin to turn northward then northwestward Monday night through Tuesday as the cyclone moves around the periphery of the larger low. The model track guidance continues to be in excellent agreement on this scenario, and the latest NHC track forecast is little changed from the previous one. A cold front associated with the low east of Newfoundland has already begun to interact with the circulation of Julian, as noted by dry air being pulled into the southern portion of the circulation, and linear banding developing to the south of the cyclone. Baroclinic forcing could allow for some slight additional strengthening through tonight. However, Julian should cross the 26 C isotherm this evening, and reach waters of 22 C by 24 h while interacting with the cold front and associated mid- to upper level trough to its north. These factors should cause the cyclone to go through extratropical transition tonight through tomorrow morning, with the transition complete by late tomorrow. The latest SHIPS guidance as well as the FSU phase-space diagrams depict this transition scenario. Once extratropical, the system should dissipate within a couple of days over the north Atlantic. The latest NHC intensity forecast was essentially an update of the previous one, and is close to the HCCA and IVCN solutions. FORECAST POSITIONS AND MAX WINDS INIT 29/2100Z 36.7N 44.6W 50 KT 60 MPH 12H 30/0600Z 38.8N 41.4W 55 KT 65 MPH 24H 30/1800Z 42.2N 38.1W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 31/0600Z 46.3N 36.8W 50 KT 60 MPH...POST-TROP/EXTRATROP 48H 31/1800Z 51.0N 37.7W 45 KT 50 MPH...POST-TROP/EXTRATROP 60H 01/0600Z 55.0N 39.6W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 01/1800Z...DISSIPATED $$ Forecaster Latto
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