582 WTNT41 KNHC 072100 TCDAT1 Hurricane Earl Discussion Number 20 NWS National Hurricane Center Miami FL AL062022 500 PM AST Wed Sep 07 2022 The structure of Earl is gradually improving, with deep convective cold tops rotating around the core with an occasional warm spot becoming evident on both infrared and visible satellite imagery. An Air Force Reserve Hurricane Hunter mission has been flying through Earl this afternoon, and they found a peak 700 mb flight level wind of 90 kt in the SE quadrant of the hurricane. However, SFMR winds have been lower than earlier observed in the NOAA P-3 mission and the central pressure has stabilized somewhere in the 974-976 mb range. These observations support keeping the intensity at 75 kt for this advisory, which is also in agreement with the 1800 UTC Dvorak T-numbers from both TAFB and SAB. Center fixes from the aircraft show that Earl continues to move east of due north estimated at 010/7 kt, and may be in the initial stages of making a more rightward turn. The track reasoning has not changed for the next couple of days, where Earl is expected to gradually turn to the northeast and accelerate as it is caught in between a mid-level ridge to the southeast, and a digging mid-latitude trough to the northwest. The aforementioned trough is forecast to ultimately capture Earl sometime in the 60-96 hour period, though timing differences between the guidance are driving significant along track spread in the forecast by that time. The latest NHC track forecast was largely unchanged in the short-term, remaining close to the tightly clustered guidance, though was shifted a bit east compared to the prior cycle after Earl becomes extra-tropical. The deep-layer vertical wind shear is beginning to decrease over Earl, now under 20-kt in both GFS- and ECMWF-based SHIPS guidance. This shear is forecast to decrease further tonight and be 10 kt or under from 24-48 hours. Sea-surface temperatures are also expected to remain at 29 C or warmer over this same time span. In terms of the high-resolution regional hurricane model guidance, the most recent HMON, experimental HAFS-S and HAFS-A, and COAMPS-TC all explicitly show Earl becoming a Category 4 hurricane over the next 48-60h. The COAMPS-TC ensemble from the 00z cycle also indicated at least 75 percent of its members becoming a Category 4 hurricane as the hurricane passes by to the southeast of Bermuda. Finally, DTOPS RI-probabilities from the latest SHIPS run indicate a greater than 50 percent chance of a 35 kt increase in intensity over the next 24 hours. While the latest intensity forecast will not go quite that high, it does show a 40 kt increase in intensity in 48 hours still making Earl a Category 4 hurricane. While it is relatively rare to see such an intense hurricane at that latitude in the forecast period, the guidance support, plus the favorable environment of Earl being positioned in the right entrance region of a upper-level jet streak ahead of the trough should provide both good dynamical support on top of the favorable thermodynamic environment by the warm SSTs. After 60 h, Earl will likely rapidly undergo extra-tropical transition as an upper-level trough digs in and captures Earl, increasing baroclinicity and removing the deep convection as the storm moves poleward of the Gulf Stream. KEY MESSAGES: 1. Although Earl's center is forecast to pass southeast of Bermuda, the wind field is expected to grow, with tropical-storm-force winds forecast to spread across the island beginning Thursday afternoon and continuing through Friday morning. The Bermuda Weather Service has also issued a Hurricane Watch for the island. 2. Swells generated by Earl are expected to reach Bermuda by tonight and the U.S. East Coast shortly thereafter. These swells are likely to cause life-threatening surf and rip current conditions through the weekend. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 26.5N 65.5W 75 KT 85 MPH 12H 08/0600Z 27.8N 65.2W 85 KT 100 MPH 24H 08/1800Z 29.7N 64.5W 95 KT 110 MPH 36H 09/0600Z 32.0N 62.7W 105 KT 120 MPH 48H 09/1800Z 35.0N 59.4W 115 KT 130 MPH 60H 10/0600Z 38.6N 55.0W 110 KT 125 MPH 72H 10/1800Z 41.8N 50.6W 80 KT 90 MPH...POST-TROP/EXTRATROP 96H 11/1800Z 45.0N 46.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 12/1800Z 47.0N 41.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Papin