Upcoming week - August 1-7

[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.

Especially keep that disclaimer in mind this week. There is red text in one portion below.

Evaluating last week

Well, this past week seemed to really hinge on Invest 90L, which of course became Tropical Storm Don during the week. Unfortunately, I predicted no development for this disturbance, so I am automatically getting a bad grade. Invest 91L also has come awfully close to development, but hasn’t done it yet that anyone knows of. One only slightly mitigating factor towards my grade is that Don was weaker than expected. Confidence was also limited, due to how untrustworthy the models have been in recent weeks. However, I take very small comfort in that, and while I’ll give myself a passing grade, it won’t exactly be a world-beating one. My grade for this past week is a D.

Invest 91L means it looks like we have a very interesting week coming up. Let’s take a look! (and hopefully do better)

Current situation and models

Invest 91L is a very interesting animal. It seems destined to develop, but it’s been pretty slow to do so. Then again, this was pretty consistent with what the Euro had been suggesting, for little to no development prior to reaching the Lesser Antilles. That model and every other reliable one does develop this very soon, possibly tomorrow. Most, if not all, also agree that this will be a tropical storm passing through the Leeward and Virgin Islands, along with maybe Puerto Rico and Hispaniola, and then heading toward the Bahamas. From there, models are intensifying this system, but also detecting a weakness. A hurricane seems very possible, if not likely, to occur if this thing follows the projection. What’s less clear is the exact track. The current NOGAPS takes it into the Gulf of Mexico and a landfall near Pensacola. The HWRF, on the other side of the spectrum, re-curves it out to sea rather quickly, east of even the Bahamas. It has been noted in some posts that the HWRF has a rightward bias, so that will be considered in this week’s prediction. It’s also hard to ignore the NOGAPS, but that is the leftmost solution going right now. Still, if models continue to trend westward, this will be very interesting towards US implications.

Elsewhere, there is a disturbance in the western Caribbean, but it is very poorly organized and no models are picking up on it. Yeah, but we’ve heard that one before recently, right? Still it appears to be heading right to the EPAC. There is also a tropical wave behind Invest 91L. It appears to have decent organization, but right now has little in the way of deep convection. While I haven’t seen any models runs with any indication on this one, some pro mets seem to think this has a real shot at development. With little runs on this the track there is unclear, so climatology and current steering flow may really dictate this one.

There is also some chatter about a possible low in the Gulf of Mexico at the end of the week. It would be a cutoff low from a frontal system, but for now there is little indication that this will amount to much in terms of tropical development.

Recent history

Since 1960, the following storms developed in the first week of August:

Arlene in 1963
Abby in 1964
Celia in 1970
An unnamed hurricane in 1971
Belle in 1976
Bess in 1978
Allen in 1980
Cindy in 1981
Dennis in 1981
Alberto in 1988
Dean in 1989
Cesar in 1990
Bret in 1993
Alberto in 2000
Barry in 2001
Bertha in 2002
Cristobal in 2002
Alex in 2004
Harvey in 2005
Irene in 2005
Chris in 2006
Edouard in 2008
Colin in 2010

Wow, that’s a lot more storms than we’re accustomed to! 23 total since 1960, or about one every other year or so. Ten of these 23 would also go on to become hurricanes at some point in their lives. With this many storms developing, let’s just take a look at the areas of interest, with Invest 91L, the wave behind it, and the potential Gulf of Mexico low late in the week.

But before we do, let’s also note the storms still active coming into this new week. They include an unnamed storm in 1964, Anna in 1969, Alfa in 1973, and Erin in 1995.

Storms either developing or still ongoing during this upcoming week in the Main Development Region specifically include Arlene in 1963, Allen in 1980, Dennis in 1981, Dean in 1989, Cesar in 1990, Bret in 1993, Alberto in 2000, Irene in 2005, and Colin in 2010. That is a more manageable nine storms, of which five became hurricanes at some point: Arlene, Allen, Dean, Alberto, and Irene. Allen and Bret raced westward through the Caribbean. Arlene, Dean, Irene, and Colin re-curved after getting going further west. Cesar turned northwest into cool water after developing right off Africa. Finally, Dennis went through the Caribbean, but then re-curved north into Florida and then the Carolina coastline, before heading out to sea (though most of this was later in life). Basically, only two storms did not re-curve at some point after developing in the Main Development Region this upcoming week.

For the Gulf of Mexico, the following storms developed there this upcoming week: Abby in 1964, Celia in 1970, Bess in 1978, Bertha in 2002, and Edouard in 2008. Of these five, only Celia became a hurricane, and it came from a tropical disturbance. The other four all developed as cutoff lows from frontal systems. Edouard was the strongest of these remaining four, clocking maximum winds as high as 65 mph. All but one of these storms also ended up in Texas as some point in their lives; the exception being Bess, which continued southwestward into Mexico. Yes, even Bertha, despite being a dying depression, will be included in that mini-set.

So what does this all tell us?

The odds are pretty high that Invest 91L will develop, intensify, and re-curve. This is based on a combination of what models and recent history are suggesting. To say it re-curves does not necessarily imply that it will miss land, i.e. Dennis in 1981, and the NOGAPS solution into the Gulf of Mexico cannot just be ignored. However, some place further north along the East Coast is more likely to get impacted by this system, if anywhere in the US. Of course, the immediate concern is for the Leeward and Virgin Islands, Puerto Rico, Hispaniola, and the Bahamas. Several of these areas, if not all, could easily be impacted by this complex, large system.

Though I haven’t seen a model run for the wave behind it, it appears that if it develops it could follow a similar track. It is unclear if this system would strike the Caribbean or not, though the further east it develops, the less likely that would appear.

As for the proposed Gulf system, it could happen, but it will probably be limited to a tropical storm, and not become a hurricane. The odds also say that any storm would probably go to Texas. Given the large high pressure ridge over that state, the best bet would probably be the southern part for now, if it even happens.

The Prediction

Invest 91L is pretty much a lock to develop at some point, probably tomorrow. It also seems too clear that this will re-curve somewhere. The big questions are, where and when will the re-curve take place, and how strong will this system get? With some models trending westward, and so many land areas possibly being affected, this is not going to be a particularly high-confidence forecast, so be very forewarned and I urge anyone: Do NOT treat this as an official prediction! This is strictly my opinion, and given the nature of what I do here, errors are subject to be quite large. I predict a tropical depression and storm to develop tomorrow just east of the Leeward Islands. That afternoon, it will pass near Martinique and Dominica and head towards Puerto Rico and the Dominican Republic. However, due to the large size of this system, it will still produce a rain threat into the northern Leeward Islands, and the Virgin Islands. Emily’s intensification will be very gradual in the Caribbean on Tuesday and Wednesday, but pick up on Thursday as it heads towards the Bahamas and I predict a hurricane by that night. Emily will start to slow down in forward speed on Friday as it starts to feel the trough that will pick it up, but still head northwest into the central Bahamas, becoming a Category 2 hurricane, with maximum winds as high as 100-105 mph. On Saturday, the northwestward motion will continue with little change intensity, and Emily will turn north on Sunday in the northern Bahamas, still as a Category 2 hurricane with maximum winds of 100-105 mph. Confidence is 30% - I am hopeful at this point that I at least have a grasp for what is going on, but again, DO NOT treat this as an official prediction! Rather, stay tuned to the NHC and your local authorities for what to do if in the path of this potentially dangerous system! Thank you.

As for the low behind Invest 91L, another Invest later this week has to be considered, but I haven’t seen anything from models indicating that this is about to take off. Getting two storms developing in this part of the world in the first week of August is also pretty rare, but it still has a decent amount of organization; it is just lacking the really deep convection you want to see when really looking at a storm that’s about to get going. I think any development that happens this week to happen further west no earlier than probably Friday or so. But will it develop? I predict no development for this tropical wave behind Invest 91L during this upcoming week. Confidence is 60%.

As for the Gulf low, it is very hard to make a confident prediction when the situation hasn’t even begun to unfold. As a result, confidence here is also not very high, but what I can say is that it should be nothing more than a moderate tropical storm if anything happens, and probably goes to Texas. But for now, with not a high amount of confidence, I predict no tropical cyclone development in the Gulf of Mexico this upcoming week. Confidence is 60%.

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

-Andrew92

[Macrocane]

The posts in this forum are NOT official forecast and should not be used as such. They are 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.

Excelent post, maybe predicting cyclognenesis is not that hard this week because all models global, regional and tropical are in agreement plus the climatology says it's very possible as you discussed it. The track of 91L is another story and it's more difficult to forecast, I like your analysis though IMO Florida may be affected by this system. Keep up the good work!

[Andrew92]

Well it's time to evaluate.

Well Emily was certainly the interesting one to track, even if weaker than expected! This was a very low-confidence prediction, as I was hoping I got the gist of it at least, but I still try to get as many particulars down as possible. I did generally get the gist of this storm’s path, but definitely not the intensity. The environment was much less favorable than expected, though the track was close to what I was saying. About the only deviation in that end on my prediction was that this storm turned northwest far later than I was expecting. I expected that to happen as a turn to take it between Puerto Rico and Hispaniola; instead, it made the turn near Haiti and Cuba. I was correct in analyzing a rainfall threat to several of the islands while Emily was there. But, that intensity portion…ugh. This was nowhere close to having a chance to become a hurricane, with or without land.

Elsewhere, I successfully nailed no development for the wave behind Emily, the proposed low in the Gulf of Mexico (where was that again?), and anywhere else in the Atlantic.

However, it really comes back to Emily. Overall, while not a very good prediction, this was extremely tough with what I had to work with. My grade for this past week is a C-.

New week coming right up.

-Andrew92