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| #1108277 (Received by flhurricane at: 10:57 PM 21.Sep.2022) TCDAT2 Hurricane Fiona Discussion Number 31 NWS National Hurricane Center Miami FL AL072022 1100 PM EDT Wed Sep 21 2022 Just after the last advisory, a white ring in the Dvorak curve completely surrounded the eye, with cloud-top temperatures as cold as about -80 degrees Celsius. These temperatures have warmed a bit since then, and the eye is not as warm as it was. A NOAA Hurricane Hunter aircraft flew two passes through the eye and measured a peak 700-mb flight-level of 119 kt and SFMR winds of 100-105 kt, but also found that Fiona`s central pressure has fallen to 934 mb. Given the pressure drop, and the fact that satellite intensity estimates are not much lower than before, the initial intensity remains 115 kt (but this could be a little generous). The plane also found that the 50- and 64-kt wind radii have increased in size. Fiona is still moving just east of due north, or 010/9 kt. The hurricane is expected to accelerate toward the north-northeast during the next 24 hours while located along the western periphery of the Azores-Bermuda high. After that time, an even faster motion toward the northeast and north-northeast is forecast as a progressive deep-layer trough moves off the northeastern U.S. coast Thursday night and Friday, propelling Fiona toward Atlantic Canada at speeds of 25-30 kt. A slower northward motion is expected by 72 hours, with Fiona continuing across the Gulf of St. Lawrence and Labrador, and then over the Labrador Sea by days 4 and 5. The track guidance is very tightly clustered, and the new NHC track forecast is mainly an update of the previous prediction. Little change, or perhaps some fluctuations, in intensity are expected during the next 24 hours while Fiona remains over warm waters of 29-30 degrees Celsius and in a generally low-shear environment. Shear increases substantially in 36-48 hours, which should cause some gradual weakening, and extratropical transition due to the aforementioned trough is expected to be complete just after 48 hours as the center of Fiona is approaching Nova Scotia. The extratropical low is forecast to continue producing hurricane-force winds as it crosses Nova Scotia and moves into the Gulf of St. Lawrence through day 3, and it is expected to continue producing gale-force winds as it moves across Newfoundland and Labrador. The NHC intensity forecast is close to the IVCN and HCCA consensus aids during Fiona`s tropical phase through 48 hours. After that time, the official forecast more closely follows the GFS and ECMWF global models solutions. Based on the NOAA Hurricane Hunter data, the wind radii have been expanded at the initial time and within the forecast. Key Messages: 1. Hurricane conditions are possible, and tropical storm conditions are expected, on Bermuda beginning Thursday evening and continuing through Friday morning. 2. Fiona is expected to affect portions of Atlantic Canada as a powerful hurricane-force cyclone late Friday and Saturday, and significant impacts from high winds, storm surge, and heavy rainfall are becoming increasingly likely. Interests in these areas should closely monitor the progress of Fiona and updates to the forecast. 3. Large swells generated by Fiona are expected to cause dangerous and possibly life-threatening surf and rip current conditions along the east coast of the United States, the Bahamas, Bermuda, and Atlantic Canada during the next few days. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 22/0300Z 26.6N 71.2W 115 KT 130 MPH 12H 22/1200Z 28.2N 70.5W 115 KT 130 MPH 24H 23/0000Z 30.9N 68.7W 115 KT 130 MPH 36H 23/1200Z 34.8N 65.1W 110 KT 125 MPH 48H 24/0000Z 40.7N 61.7W 105 KT 120 MPH 60H 24/1200Z 45.7N 61.4W 85 KT 100 MPH...POST-TROP/EXTRATROP 72H 25/0000Z 48.5N 61.3W 65 KT 75 MPH...POST-TROP/EXTRATROP 96H 26/0000Z 54.9N 59.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 27/0000Z 62.2N 58.6W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg |
