Tropical Storm Hermine is gathering strength as it steams north-northeastwards at 14 mph towards the Florida Panhandle, and appears poised to give Florida its first hurricane strike in nearly eleven years when it crosses the coast late tonight or early Friday morning. An Air Force hurricane hunter aircraft was in Hermine early Thursday afternoon, and found top surface winds of 65 mph to the east of the center, and a central pressure that had fallen to 991 mb. The aircraft recorded a distinct double wind maximum on either side of the center, evidence that Hermine was not far from from closing off an eye. This process was also apparent on satellite images, which showed a band of intense thunderstorms rotating around the north side of Hermine’s center, forming the northern portion of an eyewall. At this rate, Hermine should have a fully closed eye by late afternoon, and could be a Category 1 hurricane by Thursday evening. It’s a good thing Hermine didn’t get its act together a day earlier, or we might be looking a a major hurricane in the Gulf of Mexico today. Wind shear continued to be a moderate 10 - 20 knots on Thursday morning, but the direction of the shear was from the west-southwest, where the upstream air is not quite as dry, as seen on water vapor satellite imagery. Sea surface temperatures (SSTs) near the center remained favorable for development, near 30°C (86°F).
Figure 2. Latest satellite image of Hermine. (10 AM CDT)
Hermine expected to become a Category 1 hurricane
The latest Thursday morning runs of our top models are in solid agreement that Hermine will make landfall along the Florida Big Bend coast on Thursday evening near midnight. In their 11 am EDT Thursday Wind Probability Forecast, NHC’s highest odds for getting tropical storm force winds of 34+ mph from Hermine along the Gulf Coast of Florida were 84%, 83%, and 71%, respectively, for St. Marks, Cedar Key and Apalachicola, Florida. The SHIPS model on Thursday morning predicted moderately favorable conditions for intensification, with wind shear staying a moderate 10 - 20 knots through landfall on Thursday night. SSTs will be a very warm 30°C (86°F), and mid-level relative humidity was predicted to be a reasonably moist 65%. Our three best intensity models--the HWRF, DSHIPS and LGEM models--were in agreement with their latest runs available late Thursday morning on a landfall intensity of 70 - 75 mph--a borderline strong tropical storm or minimal Category 1 hurricane.
The Gulf Coast of Florida can receive large storm surges, due to the extensive stretch of shallow continental shelf waters offshore that extend up to 90 miles from the coast, and NHC has increased their maximum storm surge forecast to 5 - 8’ above ground along a stretch of the Florida coast to the right of where the center is expected to make landfall. Hermine is a large storm, with tropical storm-force winds that extend out up to 140 miles east and southeast of the center, and will likely deliver a storm surge of at least 3 feet to a 150-mile stretch of the Florida Gulf Coast and potentially 1-3 feet along a 150-mile stretch of the Georgia and southern South Carolina coast. Early Thursday afternoon, Hermine continued to create storm surge heights over 1’ along the entire Gulf Coast from New Orleans, Louisiana to Naples, Florida. According to the NOAA Tides and Currents page for Hermine, the maximum storm surge early Thursday afternoon was approximately 2.0’ at Cedar Key and Apalachicola, Florida.
Extremely rich moisture available to Hermine
Near record-warm ocean temperatures in the Gulf of Mexico are evaporating near-record amounts of water vapor into the atmosphere for Hermine to feed off of....MUCH MORE