Helene continued to steadily strengthen as it grazed the northeastern tip of Mexico’s Yucatán Peninsula Wednesday morning. The storm is on the cusp of becoming Hurricane Helene and is projected to deliver a devastating blow to Florida’s Gulf Coast tomorrow as a major hurricane.
Helene is forecast to be a remarkably large hurricane, with tropical storm winds extending nearly 430 miles across as it nears Florida tomorrow.
Only four named storms this century have been as large as Helene is forecast to be over the Gulf of Mexico: Irma (2017), Ike (2008), Ivan (2004), and Isidore (2002).
Forecasts have been strikingly consistent showing a major hurricane (Category 3 or stronger) landfall in Florida’s Big Bend between Mexico Beach to the west and Cedar Key to the east. The official forecast takes the center of Hurricane Helene inland just south of the state capital at Tallahassee between St. Marks and St. George Island as a Category 3 hurricane Thursday night or very early Friday.
On its projected track, Helene is expected to deliver a life-threatening and potentially catastrophic storm surge to Florida’s Big Bend, with up to 10 feet of coastal inundation forecast for coastal Franklin County – including places like St. George Island and Apalachicola eastward to Alligator Point – and up to 15 feet of extreme surge-induced flooding into lower Wakulla County southward to Citrus County – including coastal towns like St. Marks, Steinhatchee, and Cedar Key.
Even coastal locations along Florida’s Gulf Coast well removed from Helene’s destructive core could see significant inundation due to its massive wind field. Up to 8 feet of storm surge is forecast into parts of Tampa Bay, with an impactful 3 to 5 feet of storm surge flooding possible stretching into southwest Florida south of Port Charlotte.
Extreme hurricane conditions will be possible in Tallahassee by late tomorrow if the center of Helene tracks near or to the west of the city as currently forecast. Because Helene will be moving so quickly as it comes ashore, it will spread damaging winds far inland. Inland cities in Georgia like Valdosta, Albany, Macon, and Atlanta could see widespread wind damage from Helene and extensive power outages can be expected across the southeastern U.S. on Friday.
Worrisome flood threat for the southern Appalachians
A Predecessor Rain Event or PRE looks to unfold ahead of an approaching front across North Georgia, the western Carolinas, and southern Appalachians beginning today and extending into early Thursday. These “PREs” can occur hundreds of miles ahead of a big storm system and often set the stage for significant flood events.
The risk of extreme rainfall for these areas prompted the National Weather Service’s Weather Prediction Center to issue a rare high risk of excessive rainfall for the southern Appalachians, including parts of North Georgia, far western South Carolina, and the mountains of western North Carolina from tomorrow into early Friday.
High risks are only issued on about 4% of days but have accounted for 80% of hurricane damages and over a third of all flood-related deaths since 2010.
Helene winding up
Hurricane hunters flying Helene Wednesday morning – including small un-crewed hurricane hunting drones – found a steadily strengthening storm and falling pressures, with the storm nearing hurricane strength.
Satellite showed organizing and increasingly robust thunderstorm activity near and over Helene’s center, while radar out of Cancun showed a developing core as the western edge of Helene clipped the Yucatán Peninsula.
Little will prevent Helene from continuing to strengthen – perhaps rapidly – over the next 24 hours, especially as it emerges over the Gulf of Mexico later today.
Its forecast path takes it directly over some of the warmest, deepest waters in the Gulf, which is at record warmth for the time of year.
Intensity guidance continues to paint a bullish picture of Helene strengthening into at least a Category 3 hurricane prior to landfall, with the most aggressive hurricane models like the HAFS rising above the Category 3 threshold.
The bottom line is the Florida Big Bend should be preparing for a major hurricane hit.
For those living in or visiting places under evacuation orders, please heed the advice of local officials and seek shelter away from the storm surge threat. In many cases, you need only travel a few miles inland to find higher ground. Water, not wind, is historically the deadliest hazard of a hurricane.
If sheltering in place from the wind, find the most interior room (away from doors, windows, and outside walls) on the lowest level not at risk of flooding.
No let up in the Atlantic behind Helene
As we discussed in newsletters last month, there was reason to suspect a busy back part of the hurricane season. Longer range models are now pointing to a busy stretch behind Helene heading into October.
At least the systems being monitored today should stay out to sea. We’ll need to keep an eye out once October rolls around as other systems take shape across the Atlantic.
