We’ve got a wonderful stretch of below average but sunny, fall-like weather ahead of us over the weekend. The main weather story lies far to our south as Florida braces for Hurricane Irma over this same time period. Irma has weakened a bit but is still a large and dangerous Category 4 storm capable of wreaking havoc over the entire state of Florida.

Rest of today – our weather will be dictated by an area of high pressure anchored over the Great Lakes. This will give us mostly sunny skies with a cool high in the mid-70s.

Saturday – sunny with temperatures in the low-70s as the high pressure over the Great Lakes moves east a bit.

Sunday – more of the same as Saturday with sunny skies and high temperatures in the low-70s.

Monday – slightly warmer with high temperatures creeping back into the mid-70s with some more clouds.

Hurricane Irma a Major Threat to South Florida

Current Situation

Hurricane Irma has been weakening in the last 12 hours. It’s evident the storm is undergoing an eyewall replacement cycle, where the inner eye of the storm collapses and is replaced by a larger, outer eye. During these internal cycles, max wind speeds often decrease and fluctuate before the storm consolidates a new eye. It has been downgraded to a Category 4 storm with maximum sustained winds of 150 mph.

Headlines

• Landfall somewhere in South Florida over the weekend is a near certainty. Outer bands from Irma are expected to reach South Florida overnight tonight. Life-threatening storm surge inundation and damage from winds of major hurricane force (115 mph) are a near-certainty for parts of South Florida.
• Since midday yesterday, forecast models have trended slight back towards a westerly solution for the forecast track of the storm. This almost eliminates the risks to Georgia and South Carolina coastal areas from a direct hit from a major hurricane. However, the risk to these areas from storm surge and strong tropical storm force/marginal hurricane force winds still exists.
• There is still a chance Irma could make landfall on Cuba. This would weaken the storm ahead of subsequent landfall on Florida.

Forecast Track

As mentioned above, the best performing forecast models have shifted back to a more westerly track for Hurricane Irma.

Forecast Intensity

While Irma has weakened to a Category 4 storm due to an ongoing eyewall replacement cycle, it remains an extremely dangerous storm with an expanding wind field due to this cycle. Hurricane force winds extend 70 miles on each side of the eye and tropical storm force winds well beyond that. It remains possible that Irma can re-strengthen if it completes the eyewall replacement cycle before it interacts with land. Mid-level wind shear remains negligible and Irma will soon be passing over very warm seas with increasing depth. Both of these factors would suggest it maintaining Category 4 strength or possibly re-intensifying to Category 5.

Uncertainties

• Any landfall on Cuba or interaction of the core of the storm with the high mountains of that island would disrupt the storm and cause weakening. This would be good news for Florida, at the expense of Cuba of course.
• Should the core of the storm avoid Cuba and close off a new eye before too much time elapses, it would have the possibility of re-strengthening before landfall. A strong Category 4 or even a Category 5 storm making landfall on Florida is not out of the question.