|
Show Selection: |
| #1107611 (Received by flhurricane at: 11:03 AM 17.Sep.2022) TCDAT2 Tropical Storm Fiona Discussion Number 13 NWS National Hurricane Center Miami FL AL072022 1100 AM AST Sat Sep 17 2022 Fiona is going through some structural changes this morning. From a zoomed-out view on satellite imagery, Fiona appears better organized compared to previous days, with the convective envelope becoming more symmetric, and upper-level outflow expanding around most of the storm. However, Air Force Reserve and NOAA Hurricane Hunter aircraft data indicate that the central part of the circulation still lacks some vertical coherency. From the best we can tell from the aircraft data, the low-level center appears to be re-forming farther east near a recent burst of deep convection. The central pressure may have risen a bit during this re-organization process, but maximum winds are still estimated to be 50 kt. With the center re-formation, the initial motion has become more uncertain, although Fiona has definitely slowed down from yesterday. The longer-term average motion is 275/7 kt. The track forecast reasoning remains unchanged, with Fiona expected to gradually recurve around the western extent of the western Atlantic subtropical ridge through the 5-day forecast period. The big change, however, is that the adjusted initial position due to the center re-formation has tugged all of the guidance eastward on this cycle. The new NHC forecast is also east of the previous one and lies close to the HCCA and TVCN consensus aids, now showing a track near or over the western part of Puerto Rico in about 36 hours. The caveat to this forecast is that additional center re-formations could cause models to shift again, and therefore there`s quite a bit of uncertainty in the short-term track forecast. Especially in cases like this, users are reminded to not focus solely on the track forecast itself, and to account for potential shifts in the track east or west. The upper-level environment over Fiona has improved, and deep-layer shear is expected to be light to moderate for the next several days. In fact, along with a favorable thermodynamic environment, the Rapid Intensification Indices have increased, and now show a 1-in-3 chance of a 30-kt increase over the next 24 hours. There is some uncertainty as to how quickly Fiona can take advantage of these favorable conditions given its current structure. But either way, intensification is anticipated, and Fiona is likely to be near or at hurricane strength while it moves near Puerto Rico on Sunday. The NHC intensity forecast has been increased from the previous prediction, but it still lies below the intensity consensus aids. If Fiona gets better organized today, then it`s possible that additional increases to the intensity forecast will be forthcoming later today. Key Messages: 1. Hurricane conditions are expected across portions of Puerto Rico Sunday and Sunday night, and are possible across the U.S. Virgin Islands tonight and Sunday. Tropical storm conditions will continue to affect portions of the Leeward Islands today and will spread westward to the U.S. and British Virgin Islands later today, and to Puerto Rico tonight. Tropical storm conditions will reach the Dominican Republic by Sunday night. 2. Heavy rains from Fiona will spread west to the British and U.S. Virgin Islands and Puerto Rico today, the Dominican Republic Sunday, and the Turks and Caicos Monday night. This rainfall is likely to produce considerable flood impacts including flash and urban flooding, along with mudslides in areas of higher terrain, particularly in Puerto Rico. 3. Fiona is forecast to strengthen while moving near Puerto Rico and the Dominican Republic through Monday, and interests in the Turks and Caicos Islands and southeastern Bahamas should continue to monitor forecasts for the storm. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 16.3N 63.5W 50 KT 60 MPH 12H 18/0000Z 16.6N 64.6W 55 KT 65 MPH 24H 18/1200Z 17.3N 66.0W 60 KT 70 MPH 36H 19/0000Z 18.2N 67.3W 65 KT 75 MPH...NEAR PUERTO RICO 48H 19/1200Z 19.2N 68.3W 70 KT 80 MPH 60H 20/0000Z 20.4N 69.2W 75 KT 85 MPH 72H 20/1200Z 21.6N 70.0W 80 KT 90 MPH 96H 21/1200Z 23.9N 70.6W 85 KT 100 MPH 120H 22/1200Z 27.6N 69.7W 90 KT 105 MPH $$ Forecaster Berg |
