09/04/2017
are you prepared for possible hurricane impact?
SUNDAY IRMA UPDATE
I know you want answers now, but here's the blunt truth: It is still much too early to determine what impacts, if any, Irma will have on the United States. The hurricane is still a week or so away from any potential impact. Regardless, you should make sure you have your hurricane plan in place. If you never have to use it, great. If you do, you're ready.
Nothing I tell you here today is going to get any location from Texas to Maine completely off the hook. With that said, an in depth analysis of the models and their trends over the past few days reveal a few things worth noting.
Let's talk about intensity first. No doubt Irma is a strong hurricane and will be for days. Could it become a category 5 (winds >156mph) hurricane? Yes. Is it a guarantee? No. Water temperatures are warming and the air is increasingly moist, but land interaction or the lack there of, and the amount of wind shear in Irma's path could cause the storm to strengthen or weaken. Additionally, if Irma is relatively close to the U.S. there will be tons of dry air over land that could get sucked into the storm reducing its strength. I've seen forecast models that are predicting a very intense hurricane. Fact is, these same models have way OVER forecast the intensity of almost every storm this season. Bottom-line, Irma's intensity could fluctuate a lot over the next week, but count on it being a major hurricane (cat 3 or higher).
Where is Irma headed? My confidence is high that Irma passes near the northern Lesser Antilles Tuesday and Wednesday, but once again (and really no surprise), by next Thursday and Friday, there is considerable spread in the forecast models. Even though confidence is low in the long range, for several days now, the models have been consistently showing the chance that Irma heads to the Gulf of Mexico is falling. Based on these trends, I would put the odds of it tracking there at 10%. The chance of it impacting the east coast OR tracking out to sea is 45% each. The focus has shifted to the east coast/out to sea scenarios thanks to the upper-level steering flow. I know that a substantial trough develops along the eastern seaboard Wednesday and Thursday, but the shape, strength, and duration of that trough are notoriously hard to forecast.
Does the trough stick around long enough to pick Irma up and deflect it out to sea? Or, does the trough lift out allowing the Atlantic high-pressure ridge to force it closer to the coast? I just don't know this far out. I hope to have a much better idea by Tuesday. By then, the energy that will eventually produce the trough reaches the U.S. where we have a much better network of observations at the surface and aloft. Additionally, the National Hurricane Center will fly their high altitude plane (G-IV) that will sample the environment around the hurricane to get a better idea of the steering currents. Hopefully, this wealth of info will help me whittle the potential track down some.
KEY POINTS
1. Irma is likely to be a strong hurricane for a long time.
2. No credible forecast can tell you this far out who will be threatened along the east coast, if anyone.
3. Any hurricane threat would be after September 10th.
4. I'll have a better idea by Tuesday when more data is assimilated into the models.
5. Stay aware and be ready to take action if the threat increases.
