Issued at 1100 PM AST Sun Aug 17 2025
531 WTNT45 KNHC 180255 TCDAT5 Hurricane Erin Discussion Number 27 NWS National Hurricane Center Miami FL AL052025 1100 PM AST Sun Aug 17 2025 Erin appears to have successfully completed its eyewall replacement cycle (ERC) that began yesterday. A F-16 SSMIS pass at 2314 UTC showed just a single eyewall with Erin that also appears to be contracting. Thus, Erin appears to be re-intensifying but now with a larger 20 n mi radius of maximum winds. Satellite intensity estimates, both subjective and objective, are starting to increase again. Notably, we received a T6.0/115 kt subjective Dvorak intensity value at 00 UTC. The DMINT value associated with that earlier SSMIS pass was 113 kt, and given the improvement of Erin's structure on GOES-19 satellite imagery since that time period, the initial intensity is being increased to 115 kt this advisory, making Erin a Category 4 hurricane again. An Air Force Reserve reconnaissance mission will soon be in the core of Erin to provide updated in-situ observations of the hurricane. It looks like Erin is beginning to turn northwestward, with the initial motion now estimated to be 305/10 kt. The mid-level ridge that has been steering Erin over the last few days is beginning to split, with one ridge remaining parked over the Ohio Valley in the United States, but another ridge becoming positioned more eastward of Erin. This pattern will allow a weakness to form north of Erin, enabling the large hurricane to turn northward and then northeastward roughly between the Outer Banks of North Carolina and Bermuda. The track guidance this cycle have not made very many adjustments, and thus the latest NHC forecast track looks quite similar to the prior advisory, just a little slower over the next 48 hours. This track lies roughly in between the Google Deep Mind ensemble mean (GDMI) and HFIP corrected consensus approach (HCCA). Now that Erin has completed its ERC, there is a short-term window where additional intensification could occur while the hurricane remains over warm waters near 29C and light to moderate northwesterly shear. There are a couple of complications that make the intensity forecast tricky beyond this time period. First, vertical wind shear is expected to increase over Erin soon. If Erin also then undergoes another ERC, sometime in the 24-48 h time period, this could hasten a weakening trend, like HAFS-A/B models have been suggesting. Second, as Erin grows in size, its footprint of cool upwelling will also grow, and could potentially encroach on its inner core. Several AOML/CIMAS gliders have been near the inner core of Erin over the past 24 hours, and their in-situ observations indicate that Erin has already cooled the waters in its vicinity up to 1C over the past day. This rate of ocean cooling near Erin is likely to continue increasing as the storm grows in size and slows over the next 48-60 h. Thus, the intensity forecast shows gradual weakening beginning after a short round of intensification, which is a little lower than the previous NHC intensity forecast beyond the short-term, but still not far off from the HCCA consensus aid. Erin's wind radii have been growing in size, and are expected to continue expanding over the next few days. The expanding wind field will result in rough ocean conditions over much of the western Atlantic. It should be noted that the 34- and 50-kt wind speed probabilities beyond 36 hours in the text and graphical products are likely underestimating the risk of those winds occurring. This is because the forecast wind field of Erin is considerably larger than average compared to the wind field used to derive the wind speed probability product. KEY MESSAGES: 1. Bands of heavy rainfall will linger across portions of Puerto Rico and the Virgin Islands through tonight, but are expected to diminish by Monday. Locally considerable flash and urban flooding, along with landslides or mudslides, are possible. 2. Tropical storm conditions are expected in the Turks and Caicos Islands and in the southeast Bahamas tonight and Monday. 3. Erin is expected to produce life-threatening surf and rip currents along the beaches of the Bahamas, much of the east coast of the U.S., Bermuda, and Atlantic Canada during the next several days. 4. Interests along the Outer Banks of North Carolina and Bermuda should monitor the progress of Erin as there is a risk of strong winds associated with the outer rainbands during the middle part of the week. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 22.3N 69.3W 115 KT 130 MPH 12H 18/1200Z 23.2N 70.2W 125 KT 145 MPH 24H 19/0000Z 24.6N 71.3W 115 KT 130 MPH 36H 19/1200Z 26.1N 72.1W 110 KT 125 MPH 48H 20/0000Z 28.0N 72.8W 105 KT 120 MPH 60H 20/1200Z 29.9N 73.1W 100 KT 115 MPH 72H 21/0000Z 32.0N 72.5W 95 KT 110 MPH 96H 22/0000Z 36.5N 67.5W 90 KT 105 MPH 120H 23/0000Z 41.4N 56.7W 80 KT 90 MPH $$ Forecaster Papin