Upcoming week - October 24-30

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Andrew92
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Upcoming week - October 24-30

#1 Postby Andrew92 » Sun Oct 23, 2011 10:55 pm

The following post is NOT an official forecast and should not be treated as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Evaluating last week

This past week I predicted we would see the development of Tropical Storm Rina. I was correct on that…but it happened with the wrong system. I expected it would happen on Monday with Invest 95L. However, that disturbance never developed tropically, though it did become an impressive nor’easter by Wednesday and Thursday. Actually, the track and timing of it were not too far off, as this system headed into Florida early on and produced some heavy rains as predicted. About the only thing I really got wrong with Invest 95L was developing it, and then of course intensifying it into a strong tropical storm.

Unfortunately, if Rina did form, it obviously came from something else. She developed tonight in the western Caribbean from a surprise disturbance that models didn’t see coming until late in the week. Granted, she only has just become a tropical storm, but appears to be on an organizing and strengthening trend, so my grade is definitely hurt for this past week.

Still, Invest 95L, other than the development and intensification part, wasn’t an otherwise horrendous prediction. And all things considered, seeing Invest 96L developing into a tropical storm on Sunday night was a very tall order to pin down with what I had to work with. I give myself a C- for this past week.

But I’d like to do better this week. Let’s take a look.

Current situation and analysis

The big game is looking to be Rina this upcoming week. While just a budding storm for now, the western Caribbean is not exactly a place that’s been tapped this year for developing systems. Ocean heat content readings are some of the highest in the Atlantic Ocean, if not the highest, and this could cause Rina to strengthen quickly. Shearing conditions are also decreasing, and therefore that area is also getting more favorable. The hurdle this storm will have to jump is some mid-level dry air surrounding it. If Rina can get through this, she could easily be a big name October storm. She is currently forecast to become a minimal hurricane on Wednesday.

As for the track, a very slow west-northwestward track is expected until about Wednesday night or Thursday morning. At that point, a trough digging southeast should start to pick Rina up and turn her north and then northeast in the succeeding days. What isn’t exactly clear is where this turn will take place, and if it even does. Rina is forecast for now to be very near and possibly over the Yucatan Peninsula by Thursday and Friday. Some models, like the GFS and NOGAPS, have a weaker storm just ramming into the Peninsula and dissipating. However, some models have Rina missing the peninsula and passing through the Yucatan Channel instead, like the Euro. It is also difficult to speculate how sharp of a rightward turn this storm would make in regards to who else could get hit, in regards to a Florida hit or a Cuba hit, or even just passing through the Florida Straits. The HWRF in fact has Rina clipping the Yucatan, and then curving sharply eastward into Cuba.

The geography of any potential tracks also makes an intensity forecast late in the period very difficult, if not nearly impossible, to peg. As I said above, Rina could become a significant storm with the oceanic heat content it will have. But if Rina plows into the Yucatan Peninsula, she would weaken and wouldn’t get to take a whole lot of advantage of it. Or she could clip it, and stay about the same for a couple of days in terms of intensity.

Elsewhere, Invest 97L is approaching the Caribbean. It is currently very disorganized and development will likely be very slow to occur. But the SHIPS model does indicate that this could possibly become a hurricane in a few days, and the Canadian also likes it to develop.

Recent history

In these last days in October, the following storms have developed in the Caribbean since 1960:

Hattie in 1961
Mitch in 1998
Katrina in 1999
Michelle in 2001
Alpha in 2005
Beta in 2005
Noel in 2007
Tomas in 2010

Eight storms total in about fifty years, and seven of them have occurred in the current active period since 1995. Of this set, six went on to become hurricanes. Only Katrina (not the infamous one we all know and hate) and Alpha failed to do so, though Noel didn’t become one until it was in the Bahamas and skirting the East Coast. Also, four of these storms became at least C3 storms: Hattie, Mitch, Michelle, and Beta. It’s also hard to ignore Wilma in 2005, even though she developed a little earlier, as having been similarly strong in this area. However, all of these storms became significant storms in the western Caribbean. Noel and Tomas developed further east and were a little weaker, though they still packed their own punches in flooding and Tomas was still a C2 storm for a short time.

As for the tracks of the western storms, Hattie plowed into the Yucatan, Mitch plowed into Honduras but later re-curved as a weakened storm, Katrina just developed too close to Central America, Michelle hit Cuba and then the Bahamas, and Beta plowed into Nicaragua. Then again, Wilma was heading away from the Yucatan at this time in 2005 and then rapidly hit South Florida, the only one this time of year to do so. Only Mitch would eventually reach Florida of this set of eight storms. The eastern storms, Alpha, Noel, and Tomas, all eventually re-curved east of the US, but all also hit Hispaniola in some form or fashion.

But only 2005 had two storms in this part of the world this time of year at close to the same time. Also hard to ignore is that this has been a year of numerous underachieving storms in terms of intensity. Invest 95L looked poised to developed, but didn’t. The majority of storms to become hurricanes this year have done so much further north. Only Irene became a hurricane near the Caribbean this year, and only Katia became a (minimal) hurricane in the deep tropics this year. Katia didn’t really intensify until she was further north, too.

So what does this all tell us?

Rina reminds a little of Wilma, but will hopefully not get nearly as powerful. With this being as a year of underachieving storms, that would seem unlikely, especially with Invest 95L not getting going at all tropically last week. But Rina is obviously much better-developed and it is hard to rule out at least a moderate to strong hurricane out of this. Half the storms in Rina’s set have become that strong in this part of the world, and the waters are very untapped this year there. If she can overcome her dry air problem, and stay offshore, I would be very watchful of this brewing storm. And then it’s a real tossup where she will go from there. Historical odds suggest a low chance of a Florida strike, but it can’t be ignored either if Wilma did it in 2005, and Mitch eventually would in 1998. The intensification trend makes it seem like the plowing into the Yucatan possibility is unlikely, so this will probably re-curve, though.

As for Invest 97L, this disturbance will be fighting the high odds of having two storms in the Caribbean in the last ten days of October in one year. Only 2005 has pulled that off. With this year being a year of underachieving storms, I would like to think anything that does come from this disturbance would probably be very weak at best. Not exactly saying much, huh?

The prediction

Oh boy, what a low-confidence prediction with Rina. This storm could do a multitude of things before all is said and done. With this being a year of underachievers in this part of the world, I tend to think intensification will be slow, but no hurricane is very hard to predict if not impossible. It all depends on the dry air and land interaction. But I just see this storm re-curving in a few days. Here goes my best shot, a very low-confidence one: I predict Rina will move slowly west-northwest until Wednesday night, all the while gradually intensifying into a hurricane that same day. On Thursday, the turn will commence with Rina heading towards the northern Yucatan, namely the Cancun and Cozumel areas. The intensification trend will continue and Rina will become a C2 to C3 storm before her eye clips that area on Friday, with winds of 105-120 mph. She will then weaken as she starts turning northeast that night into the southern Gulf of Mexico and be a minimal hurricane by Saturday as she weaves through the Florida Straits, passing just south of the Florida Keys but bringing very strong winds and heavy rains. On Sunday, she will weaken to a tropical storm while heading into the Bahamas, and become extratropical that night. Confidence is 30%, so really be sure not to use this as an official prediction. Rather, refer to the the NHC, NWS, and your local authorities for how to handle if this storm affects your area.

Invest 97L is being talked about by models, but it just doesn’t look too healthy and I am not buying into this one that much. If it looks like this now this year, and history is against it, that’s about enough for me, though confidence isn’t as high as I’d like. I predict no development for Invest 97L. Confidence is 70%.

Elsewhere, I predict no tropical cyclone development this upcoming week. Confidence is 85%.

-Andrew92
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#2 Postby Andrew92 » Sun Oct 30, 2011 10:42 pm

Time to evaluate!

It was all about Hurricane Rina this past week. This was a very low-confidence prediction, and to be fair I was off on timing of intensification primarily. However, there were some victories to take from this storm as well. For one thing, I did a great job on the early to mid-week part of the track, and timing of it. I predicted a slow track to the west-northwest until Wednesday, followed by a gradual re-curve before clipping the Yucatan Peninsula on Friday. Rina did make very slightly west of where I thought and the center briefly came onshore in the Cancun area on Friday, but not nearly enough to affect my performance significantly. As for intensity, I was dead-on in terms of the range for peak intensity, calling for somewhere between 105-120 mph, and it peaked at 110 mph. You look at those things, and I definitely got a fair amount of Rina’s prediction right – and nailing peak intensity for a storm like this is always commendable.

My issues with Rina were the timing of that intensity, along with what happened after Friday. I thought Rina would only intensify gradually, but decided to quickly become a hurricane on Monday instead of Wednesday. I also predicted the peak intensity would happen on Friday as she reached the Yucatan, but it happened on Wednesday instead. Instead, Rina was a tropical storm when she came onshore near Cancun, and a very disorganized one at that. Lastly, the weakening trend was much faster than I anticipated, and I never would have predicted dissipation as early as Friday in the Yucatan Channel. Perhaps if I was doing this week over I could have seen it happening near Cuba on Saturday, but not where and when it took place. Still, the Euro almost perfectly nailed that part of Rina day in and day out, so I probably should have looked into it a little more.

A well-executed track, pinning the timing of landfall and almost the exact location to the dot, and nailing what the peak intensity would be were all big plusses with Rina’s prediction. The timing of intensity is the only significant issue at hand, and probably is to blame for my Friday and weekend woes with this storm. Still, for looking that far out with a storm so hard to predict, this was not a bad prediction at all. Oh, and there’s that matter of correctly predicting no development for Invest 97L, and nothing anywhere else in the Atlantic. I give myself a B for this past week.

A new week coming up in just a few.

-Andrew92
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