NWS: Storm Surge from Hurricane Michael Could be “Catastrophic”

10 minutes ago
Originally published on October 8, 2018 9:41 pm

Hurricane Michael continued to strengthen Monday afternoon, and with a forecast becoming more certain of a direct hit, a Hurricane Warning was issued for the entire Florida Panhandle. A Storm Surge Warning was also issued from the Emerald Coast to the Nature Coast, where a life-threatening inundation of water is now likely.  

 

 

 

Hurricane Hunters found that Michael had strengthened a bit Monday evening.  As of the 8 pm advisory, the National Hurricane Center said the season’s seventh hurricane was near the western tip of Cuba and producing winds up to 85 mph.  Michael had accelerated a bit and was moving north at 12 mph.

There has been little change to the track forecast for Hurricane Michael over the past 12 hours. Forecasters from the National Hurricane Center continue to suggest they have relatively high confidence in a landfall somewhere between Destin and Apalachicola. However, timing of this landfall is still a bit in question due to model differences on the forward speed of Hurricane Michael beyond Tuesday. The GFS, for example, brings Michael well inland by Wednesday afternoon. In contrast, the European model is much slower and doesn’t bring Michael inland until early Thursday.  If a slower solution materializes, it is possible Michael could weaken some before landfall and even turn a little to the northeast, placing more of Florida’s Big Bend and Nature Coast in line for direct impacts.

The average track error at landfall, which is about 48 hours from the last advisory, is about 74 nautical miles from the center. Potential impacts from Hurricane Michael are likely to spread up to 200 miles from where the eye makes landfall, especially on its eastern side.  As of the 8 pm advisory, tropical storm force winds were already extending up to 175 miles from the center.

 

Life-Threatening Surge

 

A Storm Surge Warning has been issued from the Okaloosa/Walton County line to the Anclote River, which is near the Pasco/Pinellas county line. A life-threatening inundation of water is likely in the warned area, with the height of the water above normally dry ground potentially reaching 8 to 12 feet in areas from Indian Pass to Cedar Key.  In a statement issued early Monday evening, the National Weather Service Tallahassee said water level rises this high could potentially be “catastrophic” to the northeast Gulf Coast.

 

Other storm surge inundation forecasts include 6 to 8 feet from Cedar Key to Crystal River, 6 to 8 feet also from the Okaloosa/Walton county line to Indian Pass, and 4 to 6 feet from Cedar Key to the Anclote River.  A 2 to 4-foot surge will be possible along the coast further south in to the Tampa Bay metro area, and further west to the Alabama/Florida border.

 

In his forecast notes supporting the 5 pm advisory from the National Hurricane Center, Hurricane Specialist Dan Brown noted that the location and magnitude of peak storm surge flooding would be “very sensitive to small changes in the track, intensity and structure” of the hurricane.  And since there is still some uncertainty in all of those parameters, the official NHC storm surge forecast included “various plausible scenarios”.

 

Extreme Wind Risk

 

Every county in the Florida Panhandle has been placed under a Hurricane Warning, which also extends into coastal Taylor and Dixie counties. Further inland and farther south along the west coast of Florida, a Tropical Storm Warning was in effect to the Pasco/Hernando county line, and a Tropical Storm Watch extended as far south as the mouth of the Pearl River.

 

  The Hurricane Warnings are issued when winds of 74 mph or greater are possible during the event, but also when tropical storm force winds are likely within 36 hours. When the latter arrives, it will make completing hurricane preparations nearly impossible. Due to the aforementioned uncertainties of the storm’s eventual intensity, track and structure, how extreme the winds may get at any particular location is still a bit difficult to pin down.

 

What is clearer, however, are when the tropical storm force winds may arrive, and we’ve listed some “most likely” times of arrivals below, from earliest to latest.

 

The most likely arrival times of tropical storm force (39+ mph) winds:

  • Tuesday 8 pm: St. Petersburg/Tampa
  • Wednesday 12 am: Crystal River, Apalachicola, Panama City, Destin, Pensacola
  • Wednesday 8 am:  Gainesville, Lake City, Tallahassee
  • Wednesday Noon: Jacksonville

 

Inland Flood Risk

 

Hurricane Michael could produce enough rain over a short amount of time that leads to flash flooding of many low-lying areas near where the storm comes ashore.  Rainfall amounts of 4 to 8 inches are expected over a large area from Panama City to Tallahassee, potentially spreading as far east along the I-10 corridor as Lake City.

 

Lower rainfall amounts of 2 to 4 inches are expected along the Nature Coast and inland areas of North-Central Florida, but here too locally heavy rain could cause flooding in poor drainage areas.  The story will be similar for areas west of where Hurricane Michael comes ashore, with isolated flooding possible as far west as Pensacola.

Tornado Risk

 

Most landfalling tropical storms or hurricanes bring with them a tornado risk, and it’s usually greatest on the right side (or in this case, the eastern side) of the storm’s track.  Outer bands from Hurricane Michael could produce isolated tornadoes with little notice over portions of the Florida peninsula Tuesday afternoon through Thursday. Residents in these areas are encouraged to have a way of being alerted should a warning be issued.

 

The Florida Public Radio Emergency Network will provide hourly updates on Hurricane Michael to your local NPR affiliate beginning Tuesday morning, along with several live streaming updates on the Florida Storms Facebook and Twitter accounts.

 
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