Hurricane Irma Strengthens Again, Severe Impacts Likely in Florida

Good morning! While our weather remains calmer, we have been monitoring Hurricane Irma very closely this weekend. Irma had been moving west-northwest along the north-coast of Cuba on Saturday. This was due to a stronger sub-tropical Atlantic ridge to the north of Irma, stronger than much of the model guidance had previously indicated. Irma had also weakened from a Category 5 hurricane to a Category 3 hurricane, from more land interaction with Cuba. But Irma has now restrengthened to a Category 4 hurricane with 130mph maximum sustained winds this morning over the Florida Straits and is moving slowly northwest towards the Lower Florida Keys.

Irma is now beginning to interact with a mid-level trough over Northern Gulf of Mexico. Irma will turn even more north-northwestward today, as shortwave energy with this trough begins to phase with Irma. After moving over the Lower Florida Keys this morning, Irma’s eye will likely make landfall somewhere along the Southwest Florida coast late today or tonight. Irma’s inner core remained largely intact after leaving Cuba — and Irma just completed an eyewall replacement cycle, with the inner eyewall collapsing and the outer eyewall contracting. This has lead Irma to restrengthen again.

Irma will continue to be moving over very warm waters in the Southeast Gulf of Mexico. But southwesterly shear from the mid-level shortwave trough, will also be increasing today. Therefore, we don’t think it is likely that Irma will strengthen back to a Category 5 hurricane — some weakening is possible right before landfall. But if shear remains stronger to the north of Irma, it may enhance upper-level outflow, resulting in some intensification just off the Southwest Florida coast. There is generally lower confidence and poorer skill in forecasting hurricane intensity due to various factors. So this will have be to carefully monitored during the day.

Regardless, Irma will still likely be a dangerous, powerful hurricane until landfall. With Irma moving in a more parallel direction adjacent to the coast, it’s difficult to pinpoint exactly where Irma could make landfall. But bigger cities such as Tampa Bay should stay prepared for a direct hit from a major hurricane with sustained winds over 110 mph. A storm surge between 10 to 15 feet is also predicated by National Hurricane Center and could cause catastrophic damage along the Southwest Florida coast and Florida Keys. All preparations to protect life and property should be rushed to completion this morning.

Potential Storm Surge greater then 9 ft above ground courtesy of the National Hurricane Center

Potential Storm Surge greater then 9 ft above ground courtesy of the National Hurricane Center

It appears, on this more westerly track, that Southeast Florida, including Miami metro region, will avoid seeing more destructive, higher end hurricane-force winds and storm surge from Irma. But hurricane wind gusts between 75 to 90 mph are still likely. Thus hurricane warnings are still in effect for much for Florida. These winds could still bring down some trees and power lines, resulting in many blocked roads and power outages throughout the Florida Peninsula. Very heavy rainfall totals between 10 to 20 inches are also likely over all of South Florida. This could result in some significant flooding in many areas. There is also the potential for a few tornadoes, from the outer feeder bands of Irma today. A tornado watch has been issued for much of Florida Peninsula until at 12pm today.

Later Sunday night, Irma will be likely be tracking inland over Northern Florida, then into Alabama or Georgia on Monday. It will be weakening rapidly down to Category 1 hurricane late tonight and then a tropical storm by Monday. But some major impacts and hazards are still likely to occur. Heavy rainfall in order of 5 to 10 inches and some flash or river flooding is likely. Strong winds gusts  between 60mph to 75mph and a few tornadoes are still possible, especially on the eastern side of the storm. By Tuesday and Wednesday, Irma will continue weakening into a tropical depression and then a non-tropical low, as it moves underneath the cut-off low developing over the Tennessee Valley. Significant weather hazards from this system will be gradually be diminishing.

ECMWF model with maximum potential winds gusts in knots through Monday from Irma over next few days

ECMWF model with maximum potential winds gusts in knots through Monday from Irma over next few days

Meanwhile, back closer to home, over the Northeast, more tranquil weather continues for the rest of this weekend and into Monday. High pressure from Southeast Canada will remain control with plenty of sunshine each day and temperatures cooler than normal. High pressure will begin departing on Tuesday. This will allow the cut-off low and what’s left Irma to gradually move northeastward and bring more unsettled weather with chances of showers or thunderstorms into parts of the Northeast for the middle to later part of the week.

Hurricane Jose which is currently a Category 4 with 130mph winds as well, is passing north of Leeward Islands this weekend. Then it will meander well out in the Western Atlantic, as steering currents weaken behind an upper-level trough, for much of this week. Jose will also likely weaken somewhat over the next several days, as more mid-level shear and dry air comes in behind the trough, over Jose. However, latest models indicate that Jose may restrengthen again and might be steered back towards the US east coast, underneath sub-tropical ridging building back in the Western Atlantic and with some shortwave energy left behind by the cut-off low. However, these solutions are very far out and typically unreliable at this range. Whether or not Jose directly impacts the US, some swells from the hurricane could cause some higher surf and rip currents along the shores and beaches during the week.

Stay tuned for more public/premium articles and tropical weather dashboard updates on Hurricanes Irma and Jose through this weekend and next week. Due to the potential severity of Irma’s impacts on Florida we are removing the paywall on these premium articles on Irma. If you want to see more of these types of articles on a more normal basis in the future, you can inquire or sign up for our client or premium services on our website home page.  Also head over to the 33andrain forum  for more discussion on Hurricanes Irma and Jose and other weather over the Northeast.