Issued at 1100 PM AST Fri Aug 15 2025
759 WTNT45 KNHC 160258 TCDAT5 Hurricane Erin Discussion Number 19 NWS National Hurricane Center Miami FL AL052025 1100 PM AST Fri Aug 15 2025 Erin appears to be starting a period of rapid intensification tonight. The structure on satellite imagery has improved quite dramatically, with a small eye becoming more apparent on infrared satellite images within a small but cold central dense overcast. GOES-19 1-minute imagery also shows convective hot towers rotating cyclonically around, helping to make the hurricane's core more axis-symmetric. We have had a wealth of data from both the NOAA and Air Force Reserve Hurricane Hunters this evening. The Tail Doppler Radar data on board the NOAA-P3 showed that the wind field has become much better organized, especially in the northern semi-circle, with tilt diagnostics showing Erin's deep-layer circulation now vertically aligned. Within the past hour, the Air Force C-130 aircraft found 700-mb flight-level winds of 92 kt in the northwestern quadrant. This reduces to a sustained wind of 85 kt, making Erin a Category 2 hurricane. The hurricane moved a little right of track earlier this evening, but smoothing out the wobbles, the latest motion still appears to be west-northwestward at 290/16 kt. Not much has changed with the track philosophy, with a large subtropical anticyclone helping to steer Erin off to the west-northwest for at least the next 24-48 hours. Thereafter, a weakness in this ridge begins to develop, thanks in part to a series of digging shortwaves along a broad longwave trough centered just west of Atlantic Canada. This evolution in the synoptic pattern should allow Erin to turn northwestward and then northward by the end of the forecast period. The track guidance remains in pretty good agreement for the first 2-3 days of the period, but across-track spread does increase by day 5, with the ECMWF model on the left side of the guidance envelope, and the GFS on the right side. The latest NHC track forecast is quite similar to the prior one, and elects to split the difference between these solutions, close to the HCCA and GDMI track solutions. In the short-term, all factors appear favorable for Erin to intensify, likely rapidly, over the next day or two. With the development of a small inner core, low shear, warm sea-surface temperatures, and ample mid-level moisture. DTOPS guidance shows a greater than 75 percent chance of a 30 kt increase in intensity over the next 24 h, and the latest NHC intensity forecast now shows that amount of intensification over the next day, bringing Erin to Category 4 intensity by tomorrow night, and peaking at 125 kt in 36 h. The tricky part of the forecast comes after the next day, where it seems likely there will be some inner-core fluctuations due to eyewall replacement cycles, which are difficult to predict with much lead time. In addition, the models continue to show the potential for an increase in northwesterly vertical wind shear to 20-30 kt at 48-72 hours. In fact, the HAFS-A/B simulated satellite imagery show a significant degradation in structure over this time period, so the NHC intensity forecast now shows a little weakening beyond 36 h, and it could weaken more if these hurricane-regional models verify. Regardless, the combination of eyewall replacement cycles and vertical wind shear will likely lead to a dramatic expansion of the wind field of Erin, making it a large and powerful hurricane towards the end of the forecast. KEY MESSAGES: 1. Heavy rainfall tonight through Sunday across the northern Leeward Islands, the Virgin Islands, and Puerto Rico may lead to isolated and locally considerable flash and urban flooding, along with landslides or mudslides. 2. Tropical storm conditions are possible for portions of the northern Leeward Islands, where Tropical Storm Watches are in effect, beginning on Saturday as the core of Erin passes north of those islands. Gusts to tropical storm force are possible in rainbands over portions of the Virgin Islands and Puerto Rico later in the weekend. 3. While the threat of direct impacts in the Bahamas and along the east coast of the United States appears to be gradually decreasing, there will still be a significant risk of dangerous surf and rip currents along western Atlantic beaches next week. 4. Interests in Bermuda should continue to monitor the progress of Erin since there is still a risk of strong winds, heavy rainfall, and high surf by the middle part of next week. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 19.5N 59.5W 85 KT 100 MPH 12H 16/1200Z 20.2N 61.6W 100 KT 115 MPH 24H 17/0000Z 20.9N 64.2W 115 KT 130 MPH 36H 17/1200Z 21.7N 66.3W 125 KT 145 MPH 48H 18/0000Z 22.9N 67.9W 120 KT 140 MPH 60H 18/1200Z 24.0N 68.9W 115 KT 130 MPH 72H 19/0000Z 25.6N 69.8W 110 KT 125 MPH 96H 20/0000Z 28.9N 70.5W 105 KT 120 MPH 120H 21/0000Z 33.5N 69.0W 100 KT 115 MPH $$ Forecaster Papin