Major Hurricane Irma a MAJOR THREAT to Florida

September 7, 2017 - Hurricane, Uncategorized

Updated: 0057z/20:57/8:57pm

Special Post on Major Category 5 Hurricane Irma

This is a special post on the very dangerous, still Category 5 Major Hurricane Irma, which is currently ravaging the islands of Turks and Caicos, before it moves onto the Bahamas tomorrow and Saturday, and then Florida Saturday evening through to early next week.

If you have friends, family, or know anybody in Florida, pretty much all of it other than the extreme W panhandle area…tell them to either prepare for a major Hurricane (Especially S/SE/E portions), or get out while they still can safely and efficiently. 

Hurricane Irma is NOT a storm to reckon with or play around with. This is not like Hurricane Matthew which hit Florida last year. It is not like Hurricane Hermine, which also hit FL last year. It is not even like Hurricane Harvey, which had a main threat of rain. This storm, Irma, is bigger in physical size than all of those storms just mentioned, and carries a different threat due to its rock solid core circulation. It will not weaken immediately after a landfall, and even when weakening, it is weakening from max sustained winds of 175mph, not 130mph like Harvey, or 115mph like Hermine. Because of its rock solid core, it will maintain its circulation and eye for quite a while – if making a landfall in Florida, which the chances for are increasing a lot today. For some reference, here is a GIF made by someone showing Irma and Andrew side by side. Andrew was one of the worst Hurricane’s in FL history, and also a CAT5…

We have been tracking this storm for about ten days now, and the cone of where it will head has certainly shifted a far way – from a possible NYC hit, to an OTS solution, and now to a SE/Florida Focus.

Let’s focus on the forecast..

Hurricane Irma is currently churning through the Turks and Caicos going about 16mph, as a Category 5 Hurricane with sustained winds of 175mph.

The computer models are converging on the following path for Irma, however an exact landfall location is still to be determined – even with 30-50 miles, as any delay or advance in when this storm turns N will either mean it ends up further W or E across Florida. Let it be known that Hurricane Irma still has the potential to stay far enough E to spare the worst destruction, and prevent a landfall. However, that possibility seems to be diminishing.

Take a close look at the spaghetti models, notice that the ranges of tracks still cover ALL of Florida, E to W. The important thing to notice though, is that nearly all solutions make landfall as a CAT4/5 ‘Cane

Where Irma turns North will determine where eye makes a landfall, and that is proving very difficult to determine because of very weak steering currents S of Florida and in the Bahamas:

IF ANYBODY is telling you that they know exactly where Irma will make landfall, then they are wrong – nobody knows, not yet, because there is no CLEAR CUT steering path for us to say “its going here”.

WHAT WE DO KNOW? ITS HITTING FLORIDA… Whether or not it makes landfall, a coastal skirt, while much better than a landfall – will bring much devastation still.

There are some hints though, especially for a further W track up the spine of Florida, given the ULL and weak (but present) steering flow in the Central Caribbean, which will migrate somewhat ENE…

In addition to this, some more complex large scale explanation may be offered from this 500 millibar approach:

So, some bottom lines:

This storm is stronger than any Major Hurricane that has ever hit the US in the last decade, likely in your lifetime. Please, please, do not think you will be ok if you are in the direct path of it.

Given the current modelling and real time trends, my best guess at a track would be up the spine. However, know, that any delay or advance in the timing of when it turns N means it will be L or R (W or E) of the track. A storm going 16mph means that if it is delayed or advanced an hour, it could be 16 miles E or W off the track. In a state that is only ~130mi wide, that is a huge difference in location impacted. 

Another way to visualize the size of this storm is if you take the accumulated max wind speeds from the european model track today. Do not pay attention to specific track or speeds, but rather the fact that the entire state has at least Tropical Storm force winds:

Another major threat, besides winds, is the waves and storm surge that Irma will create regardless of track. See the storm surge guidance for a Category 5 storm:

The red is storm surge over 9 feet. Below is a picture of the predicted storm surge:


Miami – if this major storm goes the way we think right now, your city will be underwater. Miami Beach, Barrier Islands, SE FL…all of it will be underwater. Get out, while you still can, safely.

Most importantly, listen to your local government and officials, and pay attention to and your local NWS office. They are there to keep you safe!

Good luck!