Category 5 Irma Update – 09-07-17 [12:30 AM ET]

12:30 AM ET
Irma [19.6N / 67.0W]

A little MET101 lesson and potential ray of hope for SoFla.

Let’s get some facts together before we dive in:

1) Hurricanes are generally steered by what’s going on in the middle and upper levels of the atmosphere. Lower levels have little to do with the direction the system will move, so NO, turning all the East Coast fans on at the same time just won’t work.

2) Winds move clockwise around a high pressure, and counterclockwise around a low pressure.

So now observe a few things on the attached gif, which consists of current Infrared Satellite (“sees” infrared values of heat from clouds) and the mid-level wind streamlines (green lines) off the Florida East Coast, around the Central Atlantic High pressure (CATL-H), and further extending off the West Coast of FL.


Irma’s trajectory is about the competition of who’s steering flow will dominate and coax Irma’s movement. The CATL-H looks primed to snatch Irma out of her current driving forces. The steering pattern off the SW Coast of the Floridian Peninsula, associated with the incoming trough over the SE, is rather weak in comparison.

Putting these pieces together, it’s QUITE possible that Irma will indeed shift further E overnight, pulling a Miami/Fort Lauderdale landfall off the table. What’s good for us, means bad for someone else. Depending on IF and HOW extreme the shift is, this could put our friends up in Central/North FL or GA under the gun.

Of course, the CATL-H may:
1) maintain it’s current hold (sorry South Florida)
2) slightly retreat eastward (opening up Irma to being influenced by the incoming trough’s steering flow) – or-
3) build even further westward and force the track to shift slightly back westward (through the FL spine or along the Western half/Gulf side.

Regardless of who will win out, the northerly turn is a pretty sure thing, it’s just about who wins this tug-of-war for Irma’s attention. So basically, with many potentials still out there, keep preparing, keep paying attention, and be ready for whatever happens!

And lastly, no matter whether you evacuated, prepared, or didn’t, consider this a lesson learned for the next time these scenarios come around. Based on the preparations and reports from all over social media, it’s INCREDIBLE how seriously Floridians took this threat. In NO way should anyone feel their course of action was overreacting. You took these warnings seriously, and THIS is what keeps meteorologists going.

More to come…


Irma on the Mind???

Current position [18.5 N / 45.9 W]

First thing first. there is still A LOT of variation that can occur 7 days out! So this briefing isn’t to serve as a forecast, but as an explanation as to the components in play.



For the last few days, we’ve been waiting to see how far S and W Irma’s trajectory would dip. Like a ball that must bounce downwards before it bounces upwards, we’ve been closely watching the expected S and W dip that Irma is undergoing this weekend. The system is expected to begin it’s more northward trajectory on Mon/Tue, and therefore a narrowing of potential outcomes will only begin then. And no that doesn’t mean the final answer will appear, but a better picture will be revealed.

Now that WSW motion is indeed in place, but it initiated slightly higher north than previously modeled. A hurricane’s position is a result of the eye location, and to put it plainly, Irma’s been acting pretty shifty-eyed. The reason for this is the multiple occurrences of EWRC [eye-wall replacement cycles]: This is when a larger eye forms around an established eye. The larger eye “chokes” off the necessary moisture and the inner eye collapses. This process does weaken or prohibits further intensification during the process, but it is usually followed by a re-strengthening once the process is complete. So if the location of the eye is slightly changing, then it stands to reason that the point of where we measure it’s S and W movement also shifts.

If you’re following the models, remember that one release does NOT indicate certainty. You’re looking for consistency from run-to-tun. The GFS (American model) comes out 4 times a day. The European model is released twice a day.

Now as mentioned prior, there are many variables that will affect the trajectory of this system: The position of a high pressure located N/NE of the system, an upper level low located to the NW of the system, high and low pressure placement over the U.S. 6-8 days from now, and Irma’s interaction with any landmasses along the way or regions of increased wind shear [how winds change with height].

Three major factors are behind Irma’s current intensity, with the first two working against:
1) Its location in a region of cooler SST’s [sea surface temperatures], but by only about 1-2 degrees cooler than what’s consider tropical fuel.
2) Drier air ahead of the system is slightly wrapping into the inner regions, which dampens cloud/thunderstorm development.

But in the ‘ole gal’s favor is that its in a region of
3) Weaker vertical wind shear of about [10-15 kts] is a hurricane’s dream, as it does not destroy the thunderstorms from building vertically but still provides enough shift to keep the circulation in place.

But….Irma is moving into a region of higher SST’s (pro), moister (pro) air, and higher shear (con).
Considering all involved, further intensification is likely.

OUTCOME: For those in the U.S, take a deep breath, and consider tightening up your hurricane plans, because come next week, the time will come to either 1) pull the trigger or 2) exhale and consider yourself to have conquered yet another week during the 2017 Atlantic Hurricane Season.

But if you’re asking, “What would YOU do”, well, on this end, supplies are in place; because why not. Because what better way to actually relax this labor day weekend than to know whatever happens next week, as the picture sharpens, things are in place now. [Think of people who waited until the last minute to find solar eclipse glasses; how well did that work out?]

So, stay tuned, stay aware, and DO NOT buy into the hype anytime over the next 2 days.


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