Ian forecast: Category 4 landfall expected along Florida’s west coast Wednesday

“Avoiding a large and destructive hurricane for Florida seems very unlikely, and residents should heed the advice of local emergency management officials,” the Hurricane Center wrote Tuesday evening.

By Wednesday morning, conditions are expected to rapidly devolve, with threats of hurricane-force winds, flooding rain and a damaging ocean surge. The zone between Fort Myers and Sarasota, where computer models tend to show the storm coming ashore, may be most seriously affected.

A storm surge warning covers Tampa Bay and a stretch of the coast from Tarpon Springs in the north to Flamingo, on Florida’s southern tip; this area is also under a hurricane warning. The Hurricane Center warns “there is a danger of life-threatening inundation … from rising water moving inland from the coastline,” with the highest risk between Fort Myers and Sarasota, where the surge could be as high as 12 feet.

Hurricane Ian makes landfall in Cuba as Category 3 storm; Florida on alert

In addition to “devastating” winds potentially topping 100 mph, the National Hurricane Center is also warning that “widespread catastrophic flash, urban, and river flooding is expected across central and west Florida beginning midweek.” Some weather models suggest rainfall of up to two feet is possible in central west Florida.

Ian will leave few places in Florida unscathed. Tropical storm warnings surround the hurricane warnings, extending into the Big Bend area on the west coast and along the entire east coast. Farther north, along the southeast coast, tropical storm watches are also in effect for coastal Georgia and South Carolina where the storm is projected to head Friday.

On Tuesday, the storm had already unleashed wind gusts over 70 mph in Key West and multiple tornadoes in South Florida. Three to 6 inches of rain had also fallen in parts of South Florida and the Keys.

Key West also observed a storm surge exceeding two feet Tuesday evening, its third-highest water level on record. Videos on social media showed ocean water pouring through its streets.

Here is what to expect from each of the storm’s main threats moving forward, and when:

Storm at a glance as of 11 p.m. Tuesday

• Location: 110 miles southwest of Naples, Fla.
• Movement: Toward the north-northeast at 10 mph
• Maximum sustained winds in eyewall: 120 mph
• Category: 3
• Air pressure: 28.12 inches or 952 millibars

Ian made landfall in southwestern Cuba early Tuesday as a major hurricane. As it crossed Cuba, the storm’s peak winds modestly dropped from 125 to 115 mph, but they began to increase again Tuesday afternoon over the warm gulf waters, back up to 120 mph.

Cuba suffers total electrical outage as Hurricane Ian knocks out power

On Tuesday evening, the storm had undergone a structural reorganization resulting in a larger eye and a larger storm. Even though the storm is expected to encounter some hostile high-altitude winds and dry air in the coming hours, “it is expected that this large system will be fairly resilient,” the hurricane center wrote. “Therefore, the official intensity forecast continues to show Ian reaching the coast with category 4 intensity.”

Forecast track and strength

While still subject to shifts, weather model projections on Tuesday began to the converge on the idea of Ian making landfall between Fort Myers and Sarasota some time Wednesday afternoon or night. Because Ian will be turning eastward and moving ashore sooner than if it continued northward, there will be less time for dry air from the north to infiltrate the storm and weaken it substantially before it comes ashore.

Predicting the exact strength of Ian is a challenge. On one hand, Ian will be moving over very warm sea-surface temperatures supportive of it maintaining its strength or even subtly intensifying. Conversely, an uptick in disruptive wind shear, or changing winds with height, combined with an influx of dry air from the north will seek to weaken Ian. It appears the two will counteract to yield a net gradual weakening as Ian makes landfall.

Still, that will leave Ian as an intense hurricane until landfall, at which point a more hasty decrease in strength is predicted, as it becomes removed from the warm ocean, or its fuel. It is worth remembering that a storm’s strength or category has no bearing on how much freshwater flooding it can produce, which has become the leading cause of casualties in tropical cyclones in recent years.

The storm will be slowing down as it moves ashore, prolonging impacts to western and central parts of the Florida Peninsula. By late Wednesday night and Thursday, Ian will have begun curving northward to the northwest of Orlando, bringing tropical-storm impacts to north Florida. Ian is then expected to weaken into a depression, or remnant tropical swirl of low pressure, as it cruises through Georgia and South Carolina Friday and Saturday. Heavy downpours, breezy winds and a few tornadoes would be possible.

Sea-level rise could destroy Tampa Bay if a major storm hits

Surge

The National Hurricane Center is predicting that a 4- to 6-foot storm surge would be a reasonable worst-case scenario expectation in Tampa Bay based on the current track forecast. That’s a slight decrease from the previous 5- to 10-foot surge forecast that was predicated on the storm’s eye passing just to its north. Since then, track projections have shifted slightly to the south, somewhat decreasing the surge risk around Tampa but increasing it between Sarasota and Cape Coral, where it could reach 8 to 12 feet.

As hurricanes swirl counterclockwise, onshore winds and the greatest surge potential is found south of the center of circulation. To the north, winds will blow out of the east, off the land — thus reducing the surge.

A slight northward shift in Ian’s track would greatly increase the surge risk in Tampa Bay.

What is storm surge? What causes it during hurricanes?

That’s why storm surge warnings are in effect for Tampa Bay and areas to the south, where confidence is highest of dangerous impacts. To the north, only storm-surge watches are up for now, since the potential exists for offshore winds.

Storm surge is an increase in water levels above ordinarily dry ground. Florida’s offshore bathymetry, or the shape of the sea floor, is extremely conducive to serious flood events. That’s because of the long, shallow and gently-sloping continental shelf in the eastern Gulf of Mexico.

Imagine pushing a grocery cart up a long, gradually sloping ramp — it would be effortless in comparison to pushing it up a short, stubby or nearly vertical ramp. That’s the premise here; it’s way easier for strong winds to blow an enormous volume of water ashore.

Rain and freshwater flooding

The heaviest rain will come down near and to the north of Ian’s center. The storm will ingest dry air from the northwest as it makes landfall, which will swirl into the storm and begin slowly eroding its southern flank. That will cut back on rainfall totals south of the center, though a widespread 3 to 7 inches is still likely.

To the north, however, rainfall rates of 2 to 3 inches per hour are possible near and just north of Ian’s eye, with totals in the 12- to 18-inch range widespread and few locales seeing closer to two feet. The storm’s slow forward speed will increase the risk of serious flooding.

It’s important to remember that, in moisture-loaded environments like this, heavy rain can fall far from the center. That means places between Orlando and Jacksonville even on the eastern side of the state could see more than a foot of rain.

The weather has been anomalously wet across Florida as of late, meaning the ground is already saturated and will have a difficult time absorbing excess runoff.

Anticipated storm surge, meanwhile, will back up rivers, making it more challenging for excessive rainfall to drain to the sea. The two will conspire to further exacerbate freshwater-flooding impacts. The Weather Prediction Center notes that there is a level 4 out of 4 “high risk” of flash flooding and excessive rainfall.

Friday and into the weekend, heavy rain will spread further north into Florida and then over the Southeast and Mid-Atlantic with “considerable flooding” possible, according to the Hurricane Center.

The storm’s remnant rainfall could persist over the Mid-Atlantic into early next week.

What to know about Hurricane Ian, the storm approaching Florida

Wind

Winds will be strongest near the coastline as the storm center comes ashore — the zone from roughly Cape Coral to Tampa is most at risk.

The strongest winds will be found within the eyewall, or a semi-unbroken band of intense convection — downpours and thunderstorms — that encircle the eye. The ring of extreme winds may gust to near 100 to 120 mph at the shoreline, and 80 to 100 mph within a few miles of the coast.

Farther inland, winds gusting 65 to 90 mph will be common near the storm’s center, or within 50 miles of the coast. Farther east, winds will be mainly tropical storm force in nature.

Residents in the path of the storm should ensure their place of shelter is not at risk of being affected by falling trees.

The combination of saturated ground and high winds will greatly increase the risk of tree falls and power outages.

Tornadoes

Landfalling tropical systems often produce tornadoes in their right front quadrant, or ahead of and to the right of the center. That’s because onshore winds slow as they encounter friction from the rough land surface, while upper-level winds roar on unimpeded. That results in wind shear, or a change in wind speed and/or direction with height.

That means any towering clouds that extend vertically through multiple layers of atmosphere, like cells within Ian’s spiral rain bands, will be subject to a twisting force. That means a few quick-hitting tornadoes, probably wrapped in rain and impossible to see given low cloud bases, could form any time throughout the next several days. On Tuesday, the National Weather Service received reports of at least 5 tornadoes in South Florida.

Numerous warnings for waterspouts and tornadoes were issued across the Florida Keys on Monday night and South Florida on Tuesday, and the Storm Prediction Center has drawn level 2 out of 5 “slight” risks of tornadoes across most of southern and central Florida in their forecasts through Thursday.

Scott Dance contributed to this report.