Tropical Storm Ian predicted to become a major hurricane in the Gulf of Mexico

Tropical Storm Ian formed Friday night over the central Caribbean north of Venezuela and is expected to turn into a hurricane by Sunday night. Meteorologists expect Ian to intensify rapidly as she passes through the northwest Caribbean, possibly reaching the status of a major hurricane as she hits Cuba on her way to the Florida Gulf Coast.

Mystery still surrounds where Ian will reach, with a host of possibilities still on the table. There is some indication that a more dramatic north-northeast turn could occur before making landfall somewhere near Tampa, while other computer models simulate northward movement and final stall before landing near the Panhandle.

What do you know about the next big storm approaching Florida

The resulting forecast challenges mean it’s impossible to say how strong Ian will be when he makes landfall alongside the United States, but the above-average warming of ocean waters in the eastern Gulf of Mexico is a definite red flag for forecasters worried about a dangerous impact.

“Ian is expected to move near or over western Cuba as a strong hurricane and then approach the Florida Peninsula at or near major hurricane strength,” the National Hurricane Center wrote, “with significant impacts likely from storm surge, hurricane-force winds, and torrential rain.”

According to the National Hurricane Center, the “earliest reasonable arrival time” of tropical storm strength winds will be sometime around midday Tuesday in Cape Canaveral.

On Saturday morning, Tropical Storm Ian was 300 miles southeast of Kingstown, Jamaica, or about 570 miles southeast of Grand Cayman. It was moving from west to southwest at 15 mph. The Cayman Islands are under hurricane watch, while Jamaica is covered by a tropical storm watch.

Maximum sustained winds were recorded at the core of the storm at 45 mph. On the infrared satellite, Ian can be seen cruising with a single solid mass of convection, or the activity of heavy rain and thunderstorms, indicating that he’s starting to merge and organize more.

On Friday, the surface rotation of Ian east of the system’s thunderstorm gathering, a sign of disrupted wind shear, or a change in wind speed and/or direction with altitude, was clearly revealed that put the entire system out of action. Since then, the shear has begun to relax sharply, which means that thunderstorms don’t blow far downwind from the surface vortex. Visible satellite images indicate that surface rotation will soon pass under the rising thunderstorm, and if so, it may extend vertically. This will then serve as the stationary shaft of the vortex, or rotation, around which the storm will develop and intensify.

Rapid intensification on the way to Cuba

Once the sternum relaxes, there is nothing to hold Ian back. It moves over water with temperatures approaching 90 degrees, which means the seas are full of thermal energy to fuel the storm.

There will also be an upper level high pressure system that slides at the top, which will help “vent” Ian and the fan’s exhaust air away from the center of the storm. This will create a vacuum-like effect in the upper atmosphere to enhance upward motion, intensifying the storm as more warm, moist air in contact with the ocean rushes into circulation from below.

The National Hurricane Center is explicitly predicting a rapid intensification as Ian approaches Cuba by Monday night, at which point the storm may approach major hurricane strength.

Wild Home Cards with Predictions

It’s around Monday when the weather models start to differ significantly from one another and the forecast gets a bit more foggy. Part of that stems from where Ian is now. We can determine the system well on the satellite, but we cannot “see” where its axis of rotation is from above, because it is buried under the anvil of a thunderstorm. A Hurricane Hunter reconnaissance aircraft was flying through the storm Saturday morning to determine the storm’s epicenter.

If preliminary data shows that the center is located a little further to the southwest than originally thought, the storm could move westward toward the western tip of Cuba. That in turn could mean a route north of the Gulf rather than west of Florida.

It all comes down to whether Ian was “captured” or swept northeast by the approach of the basin, or the plunge in the jet stream carrying cold air at high altitudes, low pressure, and circulation.

The European model is more optimistic about this northeastern push towards Florida. In this model, Ian ties into the basin, curves eastward more quickly and sweeps shore toward the central coast of Florida as a major hurricane. The National Hurricane Center estimates that landfall can occur with a storm close to or as strong as Category 3 and winds greater than 100 mph.

The Hurricane Center warns that Florida could see “the potential for significant impacts from storm surge, hurricane-force winds, and heavy rain.”

According to the US GFS model, Ian “has missed her flight” and is left to the north. By the time Ian actually reaches the North Bay on the GFS model, a wedge of accumulated dry air is reducing and even weakening his strength.

Expectations continue to evolve rapidly, so it is wise to double-check for frequent updates on Ian’s progress.

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