Upcoming week - November 7-13

[Andrew92]

Evaluating last week

This past week was rather simple. I called for no tropical cyclone development, and indeed, nothing even really threatened to develop into anything tropically this past week. Not really a surprise given that it is November now and the hurricane season is winding down. There is an interesting area of thunderstorms not far from Bermuda that has sparked the National Hurricane Center’s interest, but it is still a day or two from developing. Therefore, I give myself an A for this past week.

But what could this area of thunderstorms do? Let’s have a look at this upcoming week.

Current situation and models

As noted previously, the National Hurricane Center is a bit interested in a disorganized area of thunderstorms not far from Bermuda. It doesn’t appear to be at least fully tropical in nature, and the Euro model seems to think anything that does develop would be amorphous, maybe even subtropical, and only last a couple days while heading northward. However, one must consider that this has been the most prime area this season for tropical systems to really intensify. I haven’t had a chance to really look at what other models think, so confidence may not be too high for what this system does, but the Euro did foresee such a thing potentially happening a few days ago, and here it is. Jeff Masters at Weather Underground also once said in a blog post that the most likely area for any November storms to develop this season was north of the Lesser Antilles, in an area like where this cluster of storms is. This is due to less dry air, less shear, and still decent enough water temperatures to support some sort of tropical development.

Elsewhere, the Euro does not show any other areas developing this upcoming week, and no other areas seem to be discussed on any weather boards anywhere.

Recent history

Since 1960, the following storms have developed this upcoming week, with asterisks by any storm developing north of the Lesser Antilles or near where the current cluster of thunderstorms is:

Laura in 1971
Jeanne in 1980
A subtropical storm in 1981*
Gordon in 1994

YIKES. There were only four storms that developed during this upcoming week. Three of them developed in the western Caribbean. The only one that didn’t developed about near Bermuda, where the current cluster of thunderstorm is located. That storm was also never fully tropical, remaining subtropical before losing all of its tropical characteristics. This storm actually got quite strong, with winds reaching to 70 mph as it skirted the East Coast.

So what does this all tell us?

Well, with having a lot of difficulties getting to any model outputs except the Euro, it is a bit hard to make a truly confident prediction on that cluster of thunderstorms near Bermuda. What I can say is that anything that does develop is very likely to remain subtropical in nature and last just a few days during the week. For what it’s worth, the Euro pretty much dissipates this by Thursday. Still, it looks to have a bit of a twist with it, although with very little convection, and the Euro has been on this for a few days now. It also has a nice tail of convection reach to the Lesser Antilles, another characteristic of a potential subtropical system. I don’t think whatever comes out of this turns out to be very strong, but with this being the hotbed for activity this year, and a surprising 70-mph subtropical storm in 1981 in this same area, one has to wonder if this could get a little stronger than expected.

The Prediction

I probably shouldn’t be too hard on myself for this one, as this area of thunderstorms will likely stay offshore and cause only minimal effects to land. Still, there has to be the threat of surf and beach erosion to be considered with any storm in this kind of position relative to the East Coast. I’ve seen storms cause these kinds of problems from much further out in the Atlantic, though most of them were admittedly much stronger. Still, this is not a prediction of overwhelmingly great confidence, but I find it a bit too unlikely that something does not try to develop out this mess, given the Euro’s consistency with it and the twist I am seeing in satellite pictures, even when looking at past hurricane seasons. I predict the formation of Subtropical Storm Sean on Monday. Sean will intensify a little bit on Tuesday to winds of about 50-60 mph while heading at first slowly north. Sean will not get any stronger on Wednesday, and by that night will be absorbed into a frontal system or become extratropical while heading northeast. Confidence is 65%.

Elsewhere, I predict no tropical or subtropical cyclone activity this upcoming week. Confidence is 90%.

-Andrew92

[Andrew92]

Well it is time to evaluate.

This past week was about pinning down what an extratropical low would do in terms of becoming tropical. These things are often notoriously difficult to predict on this front, just witness how bad I was early in the season. However, this time I did a pretty decent job on predicting Sean. It did become a subtropical storm slightly later than I thought, but intensified on cue to 50-60 mph on Tuesday as I thought. But I predicted a storm that wouldn't even last as long as it did. I thought Sean would be extratropical on Wednesday, but it strengthened tropically to a 65-mph storm instead, and didn't become extratropical until Friday. Still, I was right on the north and northeastward track. I should have addressed the threat to Bermuda, but it turned out to be minor.

Elsewhere, nothing developed as predicted. Overall, not a bad job at all on Sean all things considered. I give myself a B for this past week.

New week coming up shortly.

-Andrew92