Upcoming week - August 13-19

[Andrew92]

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

Evaluating last week

To put it bluntly, this past week was not too good. It all hinged, like the one before, on nailing what Ernesto would do. I was giving in to Ernesto being an underachiever thanks to lots of dry air in its core, and thought that even if it mixed it out it would be too late. But instead, Ernesto was quick to mix it out and became a hurricane on Tuesday before its landfall. Even the track prediction wasn’t up to par, as I had Ernesto clipping Honduras before a landfall in Belize; instead, Ernesto tracked north of where I predicted and struck just north of the border in Mexico, near Chetumal. At least I was accurate on Ernesto making landfall on Tuesday evening though, so this won’t be entirely blown. But I also had Ernesto not reaching the Bay of Campeche, and although close, this storm made it there for a bit anyway. The timing of final weakening on Thursday, followed by dissipation on Friday, was accurate. The main effects also appear to have been indeed in the form of heavy rains and nothing much else from this storm. I have noted that timing has been an issue in past predictions, and I did pretty well on that front with Ernesto. However, the track and intensity were just that little bit off to ruin those areas, and make my grade for Ernesto about a D+ as a result.

As for elsewhere, I was correct in predicting no re-development for Florence after its quick dissipation on Monday. I didn’t see the tropical depression coming behind it from Invest 92L, especially so soon as models were waiting until the weekend for something to perhaps develop off of Africa. However, all things considered, damage here is at least mitigated since it didn’t intensify any more than a depression, and models didn’t see this one coming. Accurately predicting no development from the tropical wave off Africa on the weekend also helps this week move up a tad, when the GFS was all over it at the time. The system is being watched as an Invest for future development, but that doesn’t count as full development. Overall, for Florence and everything else, I give myself a A-, only because that depression snuck up on me, but also everyone else.

I didn’t do so hot on Ernesto, but generally well everywhere else, despite that freak depression. But Ernesto was the chief event of the week, so my grade is decidedly more weighted there. I therefore give myself another C- for this past week.

What are we looking at for this new week? Let’s have a look…

Current situation and models

The remnants of the seventh tropical depression have reached the eastern Caribbean. We saw lots of dry air present for Ernesto, keeping that storm at bay, and it still appears to be there for this system. The National Hurricane Center gives this a 10 percent chance of forming by Tuesday night, and I tend to agree. We did learn that the western Caribbean is more favorable, namely the Gulf of Honduras. The NOGAPS model seems to suggest the remains of the depression could reach there and become a tropical storm before clipping the Yucatan. The National Weather Service in Corpus Christi, Texas, also expects this system to reach the western Gulf of Mexico and possibly be enhanced by a frontal system over Texas. The GFS also supports the idea of development in that area and heading about parallel to the Mexican coast along the Gulf of Mexico mainly during the weekend, and even stalling from there. The Euro is currently keeping the system as a tropical wave the whole time.

Invest 93L is churning out in the Atlantic, a bit west-northwest of the Cape Verde Islands. This system has little convection and will likely struggle for a few days due to the same combination that killed off Florence and that depression, per the National Hurricane Center: dry air, stronger shear, and cooler than normal sea surface temperatures. A bit later, there are some hints of a potential development in the central Atlantic this upcoming week, and this system would be a good candidate for that. This system might first try to develop on Tuesday or Wednesday quite a bit northeast of the Leeward Islands, but come up short due to dry air. If the GFS is to be verified, this will quickly re-curve to the north and then maybe develop and intensify further on about Thursday or Friday, a short distance southeast of Bermuda. The Euro also shows this track, but doesn’t show much in the way of development or intensification. Both models take the system east-northeast from there, with the Euro forming a quite powerful-looking extratropical system by late on Sunday. The GFS also shows strengthening as it moves along that path, over the subtropical latitudes.

The GFS also shows another tropical wave starting to come off the African coast at about the weekend. By the end of Sunday, this system is shown still a short distance off the coast, but not yet at the Cave Verde Islands and organizing. However, the Euro is currently not showing this scenario occurring during the weekend. Again, the dry air and shear aren’t likely to just go away, especially in an El Nino year, so it is probably best to just watch this for now and see if this may develop later in the future.

Recent history

The following storms have developed during El Nino years this upcoming week since 1960:

Dolly in 1968
Dottie in 1976
Alicia in 1983
Charley in 1986
Bret in 1987
Bob in 1991
Andrew in 1992
Cindy in 1993
Beryl in 1994
Chris in 1994
Bill in 2009
Claudette in 2009

This is twelve total storms forming in El Nino years since 1960 this upcoming week. There have been 18 El Nino years in that time. Therefore, the yearly average would be a storm not forming every third El Nino season. Then again, there were two storms during this upcoming week developing in two different years, 1994 and 2009. The latter year also still had the weak and short-lived Ana churning in the tropical Atlantic. Of the twelve aforementioned storms, seven eventually became hurricanes. However, all but two of these storms became hurricanes north of the Tropic of Cancer; the ones to buck that trend though are the most recent two, Chris in 1994 and Bill in 2009. Another trend is that all of the storms that formed in the Main Development Region were very weak there (like Bret in 1987, Cindy in 1993, and Ana in 200), and the ones that survived have tended to re-curve towards Bermuda and then over to sea with perhaps a Canadian threat, except for of course Andrew (such as Chris in 1994 and Bill in 2009).

Four of these storms formed in the Gulf of Mexico, headlined by Alicia, which moved extremely slowly before its landfall near Galveston, Texas. The others were Dottie in 1976, Beryl in 1994, and Claudette in 2009. The trend with these three storms in terms of track is that they tended to head to the north as soon as possible. They usually moved slowly at first in weak steering currents, but the currents usually sped them up about a couple days after developing. As for strength, only Alicia became a hurricane, but Beryl was strengthening quickly after just forming right offshore, and Claudette was on a roll before running into stronger shear and dry air in the northern Gulf. Also, three of these four have formed in the eastern Gulf, with only Alicia forming further west.

Three other storms formed off the east coast in El Nino years: Dolly in 1968, Charley in 1986, and Bob in 1991. All of these storms managed to become hurricanes. Dolly was quick to be steered by a westerly flow, that same flow took some time to be established for Charley, and Bob never felt until it was extratropical.

So what does this all tell us?

I think there is a very decent shot for some kind of development this upcoming week. The most likely source will be Invest 93L, but it will take some time and patience for it to do so. There is simply too much dry air and shear in its current environment, but things may change if it indeed tracks more westerly and the north with time, close to Bermuda. This kind of track is also highly suggestive of storms that form in this region during El Nino years for this upcoming week, and survive their unfavorable environments, like Chris in 1994 and Bill in 2009. Ridging is simply not that strong, troughs are stronger, and for those reasons storms usually can just not make it farther west. That appears to be the pattern for now anyway. Yes, Andrew found an unusual blocking ridge a bit later, but that storm seems like a bit of an outlier for El Nino’s. However, normally once these storms are far enough north, usually around 30-35 degrees latitude, they start making beelines to the east or east-northeast, out to open waters. That kind of track is exactly what the reliable models see with Invest 93L. As for intensity, all of the storms that come into that kind of flow around this time during El Nino years tend to find ways to become hurricanes, even if just minimal ones. Therefore, one can absolutely not be ruled out over those open waters, no matter how short its life may be.

Storms forming in the Gulf of Mexico are less common. However, the ones that do tend to be slow movers for their first couple days, and then after that tend to move quicker onshore. Then again, the eastern Gulf tends to be more favorable for development than the western part. Still, the GFS has done a pretty good job this season, so it would be a mistake to completely dismiss development. But the Euro also tends to do a good job on disturbances like this one, and does not develop this into much of anything in the Gulf of Mexico.

As for the last seeming system, again, it is very hard to get successive systems in any year in the first half of August, let alone in an El Nino year. We have just had Florence and a tropical depression that didn’t intensify further, so it may take some time for anything else to really get going in that part of the world.

The prediction

I really think we may have some activity later on this week, namely from Invest 93L. In fact, I’m even going to be a little bold on this one, after reviewing what history suggests. I predict a tropical depression to develop on Thursday a semi-short distance southeast of Bermuda, from Invest 93L. That same day, it will become Tropical Storm Gordon as it generally heads northward, turning east of north on Friday. This storm will develop slowly the first couple days, but become a hurricane on Saturday as it heads east-northeast over open waters. This status will be short-lived, and Gordon will be a tropical storm again by Sunday before becoming extratropical that night, west or northwest of the Azores. Maximum winds will be about 75-85 mph. Confidence is 70%.

The remnants of the tropical depression will be the tough one, though. This is another case of the two best models showing diverging results, and a bullish NOGAPS even shows a tropical storm in the western Caribbean. The GFS takes it slowly towards Texas into the next week as a potent system, while the Euro quickly takes it into Mexico as not much of anything. I’m not sure either will quite happen like these models are saying exactly. Here’s what I think: I predict no development of this system until it reaches the Gulf of Mexico. It will get there by the weekend and re-develop into a tropical depression on Saturday just off the Mexican coast, but not strengthen anymore before landfall somewhere between Tampico and La Pesca either late that night or early Sunday morning. Confidence is 60%.

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

-Andrew92

[rainstorm]

thanks for the forecast. nicely done

[LarryWx]

Andrew92,
I thoroughly enjoy your weekly predictions because I feel you do quite a good job, overall, and your product is rather unique. So, thank you and keep up the good work.

I do have one disagreement with you. I consider Andrew to have occurred during neutral ENSO rather than El Nino. This is based on Nino 3.4 SST anomalies and is supported by the SOI. Perhaps, you're assuming a lag period from the 1991-2 El Nino, but I haven't found assuming a lag to be the way to go in most instances, including in this case.

[Andrew92]

Larry, I actually don't entirely disagree with you on 1992. This has been the toughest year for me to prove as in fact an El Nino year. I've always considered it as such from prior education that the whole period from 1991-early 1995 was kind of a long, bizarre, waxing and waning El Nino phase. I do certainly find though that 1992 was the year with the weakest indices in the Pacific Ocean.

However, Andrew was still the only storm to strengthen at all in the tropics, and didn't really get going until at about 25 degrees latitude. Another tropical depression or two tried, but came far short of being anything respectable that year. Except for Andrew, all of the other tropical storm and hurricanes were pretty quick to take either northerly or easterly paths, with only Danielle reaching the East Coast after Andrew. Then again, I have said in my other thread about the second year after full El Nino's, that the first year does still tend to have a slightly stronger ridge, which might have helped Andrew's case. Also, those years still tend to show some unfavorabilities in the tropics for any more than about one or two significant storms. Still got a ways to go though.

Also very hard to ignore in 1992 is that that year was a record year for the Eastern Pacific, with 24 named storms. The Central Pacific also had three storms, which is very difficult to get in even strong El Nino years - even 1997, the strongest known El Nino ever, had just two. 16 hurricanes also occurred in the Eastern and Central Pacific, with ten reaching at least category 3 strength. It just seems to me that that kind of activity would be very hard to get in a year that isn't El Nino, despite what the SST anomalies might say.

But, what do I know? I don't claim to be a buff on the Eastern and Central Pacific.

-Andrew92

[TYNI]

Also interesting to note that there were few named storms by this point in the season for those years. We're ahead of all of them at the moment.

[Andrew92]

You are correct TYNI! Except the fact that a lot of them have had relative short lives, and only three now have become hurricanes. For an El Nino, this could produce quite a few storms, but this seems more due to more rainfall over Africa than anything. Unfavorable conditions still seem to be abound in the tropics, and in a typical strengthening El Nino they normally don't just go away. I'm not saying it will happen this year though, as all hurricane seasons - even El Nino ones - are different. With that, let's evaluate.

I was a little more aggressive this past week with tropical developments! We are in that middle part of August and approaching the late part, when things really kick in and get more active, and two disturbances had the potential to develop further. What’s more, I picked them both to do so, and they did, very close to when I said they would too! I had Invest 93L becoming a depression and storm on Thursday, and though it became a depression a tad earlier than expected, it did indeed become Gordon on Thursday. I also had Gordon becoming a hurricane on Saturday. I was a little worried when it started strengthening quickly on Thursday, but it leveled off until indeed becoming a hurricane on Saturday. As for the remnants of the seventh tropical depression, I had that system re-developing on Saturday and making landfall either late that night or Sunday. Well, it did become Helene on Friday, but didn’t grow any stronger, and in fact weakened before its landfall on Saturday evening. From a timing perspective on development and intensification, this was not perfect but still very solid. Remember, this has long been an issue of mine. Plus, the fact to call Gordon a hurricane for Saturday, before it was even a tropical depression, was for the time very bold, even as the forecast turned into that possibility or even likelihood after developing.

However, I still was off on a few fronts, mainly with Gordon. This storm first off, tracked a little further south and east then I expected. I thought by now it would be west or northwest of the Azores, but it actually made it to the eastern Azores instead. As bold as my prediction for Gordon becoming a hurricane was from the outset, it actually became even stronger than I thought! However, I really don’t know that I would have had Gordon topping out at 110 mph, nearly a category 3 storm, and I did think it would weaken on Sunday, which it has. However, it does hurt a bit on that front for Sunday, as I had Gordon becoming extratropical as a tropical storm. Gordon will take a tad longer to do that, and remains a minimal hurricane. As for Helene, my only real issues were that it developed slightly earlier than I projected and it got just a bit stronger than I thought, only to weaken before its landfall about when I said that would happen.

Overall, this was not a perfect week. However, I was brave enough to call Gordon a hurricane six days before it did so, and even as it was a disturbance fighting off lots of dry air. While off slightly on some areas with this and Helene, I still probably did about as well as I could have with what I had to work with. On top of it, I predicted no other storms to develop. There is a strong Invest that is close to becoming a depression, but hasn’t done so yet. In fact, I even thought this possibility was there at week’s end for this past week, but did well in not yet pulling the trigger. I will give myself a B+ for this past week.

New week coming up shortly, could be another busy one.

-Andrew92