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Oct 8, 2018

Michael strengthens to a hurricane and is forecast to make landfall in Florida as a ‘dangerous’ Category 3 midweek: Capital Weather Gang I The Washington Post



Enhanced infrared satellite loop of Hurricane Michael about to enter the Gulf of Mexico. (weathernerds.org)
Hurricane Michael is strengthening as it enters the Gulf of Mexico, and Florida is its target. The storm is expected to become a major Category 3 hurricane by the time it reaches the northern Gulf Coast on Wednesday. It will probably be the area’s strongest hurricane in 13 years.
“Michael is forecast to be a dangerous major hurricane when it reaches the northeastern Gulf Coast on Wednesday, and life-threatening storm surge is possible along portions of the Florida Gulf Coast,” the National Hurricane Center wrote Monday.
The storm surge, which is the rise of ocean water at the coast above normally dry land, could reach at least 8 to 12 feet, inundating roads, homes and businesses at the coast.
In addition, “heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of the Carolinas through Thursday,” the Hurricane Center warned.
Close to where the storm makes landfall in Florida, destructive hurricane-force winds are possible in a narrow zone, with damaging tropical-storm force winds affecting a much larger area, potentially expanding north into the Carolinas.
Through Wednesday, the zone of greatest concern spans the Florida Panhandle from Pensacola to Apalachicola, including Destin and Panama City Beach, and the Big Bend area to its east. Serious hurricane effects will not be restricted to coastal areas and may extend further inland, potentially affecting the Tallahassee area.
Florida Gov. Rick Scott (R) has declared a state of emergency for 26 counties in Florida’s Panhandle and Big Bend areas. “Families should take the opportunity TODAY to make sure they have three days of food and water, as well as all needed medications,” he tweeted. “EVERY FAMILY must be prepared. We can rebuild your home, but we cannot rebuild your life.”

The latest

As of 11 a.m. Eastern, Michael’s peak winds attained hurricane strength, climbing to 75 mph, as it moved north at 7 mph. The storm, the seventh Atlantic hurricane of 2018, was starting to form an eye. Traveling over very warm waters, with light upper-level winds, it could rapidly intensify over the next 24 to 36 hours, the Hurricane Center said.
At its current rate of speed, tropical-storm force winds should reach the northern Gulf Coast as early as Tuesday evening, after which conditions will steadily deteriorate. Landfall is projected during Wednesday — although models differ on whether it will occur early in the day or late in the day.
Hurricane watches have been posted from the Alabama/Florida border to the Suwannee River, which is just northwest of Cedar Key on Florida’s west coast. Tropical storm watches extend farther south through the Tampa Bay area to Anna Maria Island, Fla., and, to the west, along the Alabama coast.
Storm surge watches are in effect from Navarre, Fla., which is east of Pensacola, to Anna Maria Island, including Tampa Bay.

Storm effects

Storm surge
Michael is projected to strike an area that is exceptionally prone to storm surge due to the adjacent shallow shelf water and the concave shape of the coast. Like a bulldozer, the storm will be able push a vast amount of ocean water inland, potentially inundating homes, roads and businesses at the coast.
Areas to the east of where the storm center tracks will experience the greatest storm surge, and flooding will be worst around the high tides. High tides are extra high this week because of the New Moon on Tuesday.
Storm surge just east of where the center makes landfall could reach 8 to 12 feet, if the storm comes ashore around high tide. Here are some specific initial storm surge projections from the Hurricane Center:
  • Indian Pass to Crystal River: 8-12 ft 
  • Okaloosa/Walton County Line to Indian Pass: 5-8 ft 
  • Crystal River to Anclote River: 4-6 ft 
  • Anclote River to Anna Maria Island including Tampa Bay: 2-4 ft 
  • Navarre to Okaloosa/Walton County Line: 2-4 ft
Weather Underground’s Jeff Masters and Bob Henson projected that the surge could even reach 19 feet in a worst-case scenario. “There are very shallow waters along the coast where Michael is expected to make landfall, where the continental shelf extends out about 70 – 90 miles from shore,” they wrote. “The winds from the storm will thus be able to pile up a large storm surge along the east side of the storm’s center.

Storm surge watches as of Monday morning (left) and five-day rainfall forecast (right). (NOAA/NHC)
Rainfall
The Hurricane Center projects widespread rainfall amounts of 4 to 8 inches from the Florida Panhandle and Big Bend areas north into the Carolinas, with isolated amounts of up to a foot. “This rainfall could lead to life threatening flash floods,” it said.
Flooding rainfall is likely to affect some of the areas recovering from Hurricane Florence.
Heavy rain could first arrive in Florida on Tuesday night, and in south Alabama and south Georgia early Wednesday. By Wednesday night and into Thursday, heavy rain will rapidly streak north through north Georgia and into the Carolinas.

5-day rainfall forecast from National Weather Service.
The rain is expected to reach the Mid-Atlantic, including Virginia, Maryland, and Washington Thursday before rapidly exiting by Friday. Depending on the track of Michael’s remnants, southern New England could also see a period of heavy rain late Thursday.
The potential rainfall in the Mid-Atlantic and New England ranges from 2 to 4 inches with locally higher amounts. As these areas have seen heavy rain in recent weeks, flooding may become a concern here as well.
Wind
Michael’s maximum sustained winds are forecast to be around 120 mph when it strikes the coast. Winds this strong will be confined to the ring around its calm eye, known as the eyewall, and “devastating” wind damage could occur in this narrow zone. " Well-built framed homes may incur major damage or removal of roof decking and gable ends,” the Hurricane Center says. “Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.”
After the storm strikes land, this eyewall will quickly collapse and winds will weaken.
While hurricane-force winds of over 74 mph will be confined to a relatively small area, tropical-storm winds of 39 to 73 mph will occur over a much larger zone, and could potentially result in minor structural damage and many downed trees and power outages.

Elsewhere in the tropical Atlantic

Tropical Storm Leslie — which formed on Sept. 23 — is still active and probably will be through the weekend. It is forecast to become a hurricane, again, as it heads toward the Azores by the end of the week. And for being around for 16 days, it is presently centered just 115 miles from where it was when it formed.

Leslie's past track going back to September 23 with the five-day forecast track and cone of uncertainty. (Brian McNoldy, tropicalatlantic.com, NOAA/NHC)
Finally, a potent weather disturbance that recently left the coast of Africa is located near the Cabo Verde islands and has a shot at becoming at least a tropical depression this week, if not a tropical storm, before conditions become more hostile by the weekend. The National Hurricane Center is giving it a 50 percent chance of reaching tropical depression status this week, but no models suggest that this will become a threat to land. The next name on the list is Nadine.

Visible satellite image over the far eastern tropical Atlantic. (EUMETSAT)