Isaias is now forecast to become a hurricane, but the cone continues to shift east.
Tropical Storm Isaias is expected to gain hurricane strength as it swaggers toward Florida on a path that could take a swipe at the east coast of the Sunshine State from Broward County through Jacksonville.
The cyclone, a commodious swirl of tropical-storm-force gales that stretch 240 miles from its center, is forecast to top out as a Category 1 hurricane with 75 mph sustained winds and 90 mph gusts.
Its upgraded prediction triggered tropical storm warnings from south of Miami through the Treasure Coast and hurricane warnings for the northwest Bahamas.
As of the 11 p.m. advisory from the National Hurricane Center, Isaias was about 95 miles east-southeast of Great Inagua Island with 60 mph sustained winds and moving northwest at 18 mph.
[READ MORE: Volusia, Flagler can expect squally conditions as Tropical Storm Isaias approaches]
[TROPICAL STORM ISAIAS: Sandbags available in Volusia, Flagler]
Southeast Florida could begin feeling tropical-storm-force winds as soon as late Friday, with the more likely arrival time of Saturday morning. The storm is forecast to move north past Volusia and Flagler counties Sunday morning.
Isaias (pronounced ees-ah-EE-ahs) broke the record for the earliest “I”-named storm, beating 2005′s Irene, which formed on Aug. 7. Climatologically, the “I”-named storm doesn’t typically arrive until Oct. 4.
About 30% of the time, a storm travels outside the cone
The mystery of Isaias on Thursday was whether it would rally a strong center circulation after its journey over the summits of the Dominican Republic. A weaker storm could drift like a cork in a stream more to the west, meaning a wetter system for Florida.
A stronger storm likely would find a dent in the left side of the Bermuda High, which would steer it more to the north-northwest, hugging Florida’s east coast.
The official forecast is calling for the stronger storm that hugs the east coast of Florida through the Carolinas as a hurricane, then weakens to a tropical storm as it continues along the coast into the northeast.
But it’s important to note that the storm could go anywhere inside the forecast cone, not just down the center. About 30 percent of the time, the storm travels outside the cone and with such a huge wind field, effects will be felt far afield of the storm’s center.
“Like Matthew four years ago, just a little wiggle makes a difference in what is experienced on land,” said Brian McNoldy, a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science. “But unlike Matthew, this isn’t a Category 4 hurricane.”
Hurricane Matthew shaved by Palm Beach County on Oct. 6, 2016 with just 20 miles of ocean between the coast and sustained gales of 75 mph or higher.
McNoldy said the abnormally warm waters in Isaias’ path will nourish it as it moves northwest and north. The sea surface temperatures in the Bahamas and along the east coast, especially between North Florida and the Outer Banks of North Carolina, are up to 2.7 degrees warmer than normal.
Tropical Storm #Isaias continues to produce life-threatening flash flooding and gusty winds across Puerto Rico. Heavy rains and gusty winds are spreading across the Dominican Republic. Here are the 11 AM 7/30 Key Messages. More info: https://t.co/tW4KeGdBFb pic.twitter.com/sSXaNcttfP
— National Hurricane Center (@NHC_Atlantic) July 30, 2020
The next full forecast will be issued at 11 p.m.
Tony Hurt, a meteorologist in the Tampa office of the National Weather Service, said if Isaias stays far enough off the east coast of Florida, it would send dry winds out of the north to the west coast.
For southeast Florida, rainfall amounts could be as high as 4 inches through Sunday, but stalled storm bands could mean higher local rainfall and the potential for flooding.
Storm surge wasn’t considered a big threat for either the west or east coast as of Thursday, but that could change.