Upcoming week - August 20-26

[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

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.

Gordon is still out there and two Invests are trying to develop, perhaps threatening land areas down the road. Let’s take a look!

Current situation and models

Hurricane Gordon is churning out there near the Azores. This storm is weakening, and the National Hurricane Center is forecasting this trend to continue as it heads towards the Iberian Peninsula, to a tropical storm on Monday and then becoming extratropical on Tuesday. The cone of uncertainty in terms of track is very narrow and waters are getting cooler while this storm gets a bit larger in size, making this forecast a near certainty to take place.

Invest 94L is an interesting little character in the tropics. It is very close to becoming a tropical depression and is supported by the GFS and Euro as perhaps becoming a major player down the road. The GFS develops this system very slowly over the next few days, likely due to lingering dry area in this area coupled with some shearing conditions that are typical in El Nino years like this one. But by Thursday as this feature reaches the eastern Caribbean, the GFS develops it a bit further, but never overly so as it crosses the Caribbean from there. The Euro model follows the GFS’s track, but seems to develop it less, perhaps even weakening the system to a tropical wave by Thursday morning in the eastern Caribbean. The GFS then has the system passing just south of Hispaniola on Friday, over Jamaica on Saturday, and then curving towards Cuba and nearing the Gulf of Mexico on Sunday. The Euro has a similar track south of Hispaniola, but then seems to lose the system from there, only to have it back by Saturday near or over Jamaica. The Euro model also suggests a more westward track from here, versus the more west-northwesterly track given by the GFS. As we saw with Ernesto and the remnants of the seventh tropical depression, dry air and some shear are also likely to be inhibiting factors for development with this system. If it passes near or over Hispaniola and/or Jamaica, development could be impeded there too, if not some weakening present also.

It should also be noted that the GFS is consistently calling for some sort of threat from this system in the Gulf of Mexico, likely heading into the United States. Joe Bastardi also has indicated for days that something significant is likely to head in that direction by the end of August. Invest 94L will be a strong candidate to make a move like this. However, the GFS has done a lot of flip-flopping on this system, and such a scenario would be reserved for next week’s prediction. Then again, the GFS has done an amazing job this year so far, and this would be a good time to watch this system and make sure you have a plan for if this scenario were to take place.

We also saw the formation of Invest 95L on Sunday in the Gulf of Mexico, mainly from a surface trough aided by a frontal system, but also somewhat from the remnants of Helene. In terms of a naming perspective, this will get a new number and name if it develops further, to answer whatever questions may come from that angle. But enough of that. The GFS does support a weak storm coming out of this, likely strengthening the most just before a landfall along the northern Mexican coast late on Tuesday. This system never appears to get very strong before landfall, but looks to give all it has before this strike. The Euro model supports this same thought and idea, suggesting this may become a tropical storm, but not one that is overly strong and will probably be mostly a flood threat.

The National Hurricane Center is also keeping tabs on a new potential system behind Invest 94L. However, this system will have the same dry air and shear to contend with that 94L has, and will be coming right behind it. Invest 94L is also on the verge of developing, and potential outflow from it could put a damper on this system forming. I don't see any major model supporting the development of this sytem.

No other disturbances seem imminent this upcoming week per the GFS. The Euro does try to show a tropical wave off the African coast late in the week, but until I see more support from other models I am not ready to pull the trigger on development.

Recent history

These storms have developed or occurred this upcoming week during El Nino years – and despite some disagreements on 1992, until absolutely proven otherwise I will continue to include that year as El Nino due to a very strong Eastern Pacific season and shear only letting up in August of that year in the tropics, especially with storms not named Andrew did that year:

Anna in 1965
Subtropical Storm Bravo in 1972 (which later became Betty, after this week for those who don’t know)
Candice in 1976 (already active)
Dottie in 1976 (already active)
Emmy in 1976
Barry in 1983
Bret in 1987 (already active)
Andrew in 1992 (already active)
Dennis in 1993
Emily in 1993
Chris in 1994 (already active)
Debby in 2006
Ernesto in 2006
Bill in 2009 (already active)
Danny in 2009

In 18 seasons since 1960, 15 storms have either developed or were still active coming into this week, including one subtropical storm. Ten of these systems either already were or would eventually go on to become hurricanes. But only Andrew, Emily, and Bill eventually became stronger hurricanes of at least category 3 intensity. What’s more is that only Chris, Ernesto, and Bill became hurricanes at all south of 20 degrees latitude, with Bill being the only one to become higher than a category 1. Chris and Ernesto were only briefly hurricanes in these latitudes.

The storms that occur in lower latitudes this upcoming week during El Nino years have tended to really struggle in this part of the world. Eight storms occurred at all in this area either prior to this week or during it, but only three became hurricanes here. One of these storms, Emmy, did later become a hurricane is it re-curved out to sea. Also, though Andrew struggled in the tropical latitudes, it too became a hurricane after crossing 25 degrees. The other storms that didn’t become hurricanes here included Bret in 1987, Dennis in 1993, and Debby in 2006. All of these re-curved well east of the Caribbean and dissipated quickly. Even the storms that did become hurricanes tended to turn north as soon as possible. What's more, is that two consecutive tropical waves during El Nino years have never developed back to back this upcoming week.

As for Gulf of Mexico storms, none actually developed during this upcoming week there. Dottie formed in the eastern part a few days prior, but headed northeast and north, and stayed weak during its short life. After initially forming near the Bahamas and then crossing Florida, Barry headed westward and eventually became a minimal hurricane as it neared Mexico in 1983. Andrew is a whole other can of worms, but does suggest major hurricanes can occur in this area during an El Nino year this time of year. However, it would likely have to be a firmly established storm. Then again, Alicia formed on August 15 and quickly became a category 3 storm as it struck Galveston, and as we will see later Anita became an even stronger storm a little later after it too formed as a tropical storm in the Gulf of Mexico. Both of these storms also occurred in El Nino years, so that possibility can’t be ruled out. However, these storms also had at least three days to intensity over these warm waters. Barry in 1983 had about 48 hours to intensify, for what it’s worth.

But if conditions can be favorable in the Gulf of Mexico during an El Nino year, what does this area look like in other years during this part of the season? These storms took place in other years since 1960:

Brenda in 1973
Debra in 1978 (actually somewhat later as a storm but very close)
Charley in 1998
Bret in 1999 (already active)
Jose in 2005

This isn’t exactly an overwhelming sample size. However, Brenda and Bret were hurricanes with Bret even becoming a major hurricane after developing there. Charley also came close to becoming a hurricane briefly before striking Texas (not the Charley we all know of though). I’m actually being generous with Debra, but its depression did develop on August 26 and became storm a little later before landfall in western Louisiana. Altogether, you get about seven storms this upcoming week, of which three have become hurricanes. All three that became hurricanes had a good couple days to intensify in doing so, while the others did not.

So what does this all tell us?

I really shouldn’t just ignore Gordon here, because he is still churning out there. But I just see no evidence that this system won’t weaken to a tropical storm on Monday and become extratropical sometime on Tuesday. Storms like this that are leaving the picture usually go out like this, and this storm is highly unlikely to be an exception.

As for Invest 94L, this system may very well become a tropical depression and even storm on Monday, but will likely face a lot of issues on its way to being a major threat for the United States if the GFS is accurate. Lots of dry air and shear are still prevalent in the Main Development Region and in the Caribbean Sea, and the GFS and Euro models put together do not overly develop this system through Sunday. In fact, the Euro even seems to de-generate it near Hispaniola, while the GFS keeps it but still weak. Most storms developing hear do tend to go north, and Gordon just did, but you can’t always look at historic tracks. Take Ernesto and the seventh tropical depression that we also just had. These systems took westerly paths across the Caribbean, aided by a strong ridge of high pressure to the north. This ridge may be showing some signs of weakening, but not in time to keep this system from heading in that direction until reaching the western Caribbean at the least. I do give the GFS a lot of credit for the job is doing this year as a whole, and am for the most part thinking this system may barely survive the unfavorable conditions it will have to go through in order to be a more major player besides heavy rainfall. But the Euro is still one of the premier models to follow and it would be foolish to discount its scenario of an even more westward track as a weaker system than the GFS is showing.

Invest 95L looks to be heading into Mexico on Tuesday evening; the GFS and Euro simply put, both show that happening at that time. The question is, how much time will it have to strengthen? It isn’t moving much now and will likely head parallel to the coast until Tuesday, but it’s also not likely to develop into a depression until tomorrow late afternoon at the earliest. Still, the GFS does develop it about as much as possible, so it may still be a somewhat potent storm before landfall. The primary threat will probaly be, like Helene, heavy rainfall.

As for the system behind Invest 94L, it has the odds stacked squarely against it. It will have the same inhibiting factors that could slow development for the disturbance ahead of it, with potentially further shear from outflow if 94L does in fact develop. Plus, no two back to back systems have ever developed during this upcoming week in El Nino years, at least in the satellite era.

When I mentioned the ridge weakening for Invest 94L, I am referring to a trend with recent systems that supports this thought. Ernesto in fact felt a weakness for a bit in the western Caribbean, but still plowed into the Yucatan and the southern Bay of Campeche. Helene went a little bit further north of Ernesto, and Invest 95L is likely to head a little more north of Helene. This may be the sign of a trend going on, which may allow Invest 94L, whatever it may be in the western Caribbean, to take a similar track and perhaps go even more north of where Invest 95L is going. Of course that’s for even further down the road, but remember that the trend is your friend.

The prediction

So what do I personally think will happen with each system, given the information that I have? Let’s start with Gordon: I predict Gordon to weaken to a tropical storm on Monday morning and becoming extratropical on Tuesday while heading towards the Iberian Peninsula. The system will be absorbed in a frontal system or dissipate before reaching that area. Confidence is 90%.

That part was easy. These two Invests though are going to make for a very difficult prediction. But here is my best shot with Invest 94L: I predict this disturbance will become a tropical depression on Monday morning and Tropical Storm Isaac later that afternoon or evening. It won’t get much stronger for the next three days before reaching the Caribbean due to some dry air and shearing upper level winds, gathering winds of 40-50 mph the entire time before Thursday. On Thursday it will get slightly stronger south of Puerto Rico, with winds of 50-60 mph. But on Friday as it passes south of Hispaniola, it will weaken with winds of 40-50 mph both there and into Jamaica on Saturday. The mountains of Jamaica will cause Isaac to weaken further to a tropical depression, but it will re-strength a bit on Sunday while turning slightly west-northwest near the Cayman Islands and south of Cuba, with winds of about 45-50 mph as the week ends. Overall, Isaac will have plenty of obstacles this week, but will remain tenacious and try its best to survive and do so by the end of the week. For all areas that Isaac hits, the most primary threat will be heavy rainfall and mudslides, with some potentially stronger winds causing some damage in higher elevations. Confidence is 50%, but please remember not to treat this as an official forecast! Rather, please listen more to what the National Hurricane Center and your local authorities for official information and what to do in the event this system threatens your area. Thank you.

Invest 95L presents a bit easier of a prediction in track and landfall, but what about intensity? My best guess: I predict this disturbance to become a tropical depression on early Tuesday morning and Tropical Storm Joyce a few hours later. It will reach maximum winds of about 40-45 mph before making landfall in the early to mid-evening hours that day south of the border in Mexico, but north of Tampico. The primary threat will be heavy rainfall. Confidence is 60%, but like Invest 94L (likely to become Isaac) above, please remember not to treat this as an official forecast! Rather, please listen more to what the National Hurricane Center and your local authorities for official information and what to do in the event this system threatens your area. Thank you.

Elsewhere, I predict no tropical cyclone activity this upcoming week, including from the system behind Invest 94L. Confidence is 80%.

-Andrew92

[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.

The more I look at Invest 94L, which is now developing later than I anticipated, the more I'm reminded of one of the 2002 storms, Isidore and Lili. The major models are just showing a similar track and even similar intensity cycle to one or both of these two storms. Plus, if that ridge to the north weakens thanks to a trough over the Midwest, all bets are off.

But that's still a long ways away. Just some extra thoughts on that Invest as it prepares to develop further.

-Andrew92

[rainstorm]

looks like a busy week.

[Andrew92]

Oh dear... first part of Isaac was OK, but yesterday through tomorrow is looking bad in more ways than one. Not to mention I developed the wrong disturbance. Looking like one of my worst weeks yet this year.

-Andrew92

[Andrew92]

And it's time to, sigh, evaluate.

Oh my, this was not good. I’m going to start with the easiest two to evaluate, Invest 95L and Tropical Storm Joyce. I actually had Invest 95L forming into Joyce on Tuesday right off the coast of Mexico before moving inland. Well, it didn’t develop at all, but I guess proved to be no more than the rain threat that I anticipated. On the other hand, I had Invest 96L not developing at all, since no reliable models seemed to be latching on to it. This one did manage to become Joyce after all, though I am also not surprised that it was barely ever a tropical storm. But let’s face it, I blew it on both of these two systems.

And then there’s the big headline for the week: Isaac. For one thing, I had Isaac forming about 24 hours too soon, on Monday instead of Tuesday when it happened. This said, the first few days of predicting this storm were actually not too bad. I never had Isaac strengthening above about 40-50 mph before reaching the Caribbean or maybe a day beyond; indeed, as it reached the Caribbean on Wednesday, its winds were still only about 45 mph and it was disorganized. I also at least foresaw some intensification to 60 mph, but on Thursday instead of Friday. I also head Isaac continuing the westward track throughout the week, another big mistake. Then again, it was following it until about late Thursday night, and the timing of the track south of Hispaniola by Friday was also pretty good. Then things turned into a disaster for this past week. I did not foresee Isaac turning northwest into Haiti on late Friday night and then eastern Cuba for Saturday, and paralleling the Cuban coast for Sunday. Also, Isaac grew quite a bit larger and stronger than I anticipated, gathering winds of 70 mph as it made landfall in Haiti and only weakening a little before reaching the waters off of Cuba, at about 50-60 mph.

I did fair enough on the first few days of Isaac, up until about Friday morning. But I did extremely poorly elsewhere. This was admittedly a very difficult week, and the first few days are just barely enough to save me from a completely blown forecast and a failing grade. My grade for this past week is a very low-end D-.

BIG next few days coming. We are also nearing the peak of the hurricane season. New post coming shortly.

-Andrew92