From Thursday morning through Friday morning, Isaias rapidly intensified and became the first major hurricane of the season, which is conventionally defined to be Category 3+ on the Saffir-Simpson Scale. In terms of exact values, the wind speed increased from 75 knots to 105 knots in a 24-hour period, just barely meeting the criteria to count as RI. Then just as it was approaching the coastline for landfall, it weakened slightly to a 90-knot Category 2 hurricane. Radar and satellite data showed the eyewall quickly deteriorating as wind shear finally took its toll. --- https://bmcnoldy.earth.miami.edu/tropics/radar/ This is thankfully in stark contrast to what we witnessed eight years ago today when Michael rapidly intensified to a Category 5 hurricane right up to landfall just 70 miles east of where Isaias just made landfall. That radar animation is shown below for reference: --- Radar animation of Category 5 Hurricane Michael on October 10, 2018. https://bmcnoldy.earth.miami.edu/tropics/radar/ Isaias is no longer a tropical cyclone, but rain associated with it continues into the southeast U.S. over the next couple of days. I plotted up some preliminary track and intensity forecast verification for Isaias. For track, the Google Deepmind ensemble mean (GDMI) was by far the leading model guidance... it left the other conventional guidance in the dust. The National Hurricane Center's forecasts (OFCL) closely followed that AI guidance and ended up doing quite well. For intensity, it's not as clear-cut. Overall, the NHC (OFCL) has the lowest errors, then the Navy's COAMPS-TC hurricane model (CTCI) did quite well. NOAA's flagship hurricane model, HWRF (HWFI), did really well at the important 2-3-day lead times. The Google Deepmind ensemble (GDMI) does not stand out too much in this category for this storm. The Accumulated Cyclone Energy (ACE) has jumped up to about 17% of average for the date, as I eluded to in Wednesday's post. There is still nothing else on the foreseeable horizon, but if and when the tenth storm comes comes around, the next name on this year's list Josephine. * Visit the Tropical Atlantic Headquarters. * Subscribe to get these updates emailed to you. * Follow me on Bluesky