Upcoming week - August 6-12

[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.

Additional disclaimer: Due to lots of activity with Ernesto and Florence, and models potentially showing another system during the weekend, this week’s update is going to be a bit long.

Evaluating last week

This past week seemed to center on one thing: Tropical Storm Ernesto. I did correctly call for its development a little east of the Caribbean, but I called for it to form into a depression on Thursday, and a tropical storm on Friday. Both of these two events occurred 24 hours earlier than I thought. Ernesto also moved westward at a lot faster of a clip than I anticipated. I predicted by now it would be near the Virgin Islands or Puerto Rico. Instead, this storm is south of Jamaica and on a beeline for Central America and the Yucatan Peninsula. I also thought Ernesto would go a bit further north, impacting the Leeward Islands a little more than it did, and coming much closer to the Virgin Islands and Puerto Rico. However, I was actually pretty close with the intensity. I predicted a 45-50 mph storm upon reaching the Caribbean as happened, and a slightly stronger storm with winds of 50-60 mph near the Virgin Islands and Puerto Rico. And while it stayed quite a bit further south of where I predicted, the intensity near that general area was right on the money, at 50-60 mph. The primary threats have been heavy rain with this storm in the Windward Islands, but not in the other areas that I predicted. Had I predicted Ernesto to move as fast as it did, I was leaning towards it running into Hispaniola and disintegrating, or if further south being a lot weaker than 50-60 mph that it remains at about. Then again, even with these winds, the pressure has risen in this storm and drier air has been entrained into it, with the help of some lower-level shear in the area. But I never called for that to happen, and was planning on doing so for about Monday or Tuesday. But then again, at the time, none of the models seemed to foresee such a rapid westward track for Ernesto, so I probably did a relatively passable job, all things considered. I give myself a C for this storm.

However, I predicted no other developments with 85% confidence. I did mention that the GFS was trying to pick up on another development behind Ernesto, but no other models seemed to agree. Nonetheless, Florence developed on Friday anyway. It hasn’t proved to be the most intense storm ever mind you, but I really missed this one. I don’t know that I would have predicted this one looking back anyway, and certainly not with winds of 60 mph by week’s end, but I still give myself a high F for this storm.

Overall, Ernesto is given a bit more weight than Florence, and I at least did a passable job, but this week still was not a great one for me. I give myself a C- for this past week.

Ernesto and Florence are still churning out there, with Ernesto of course posing the biggest threat. Can I get back on track this week? Or do I even want to? I would love more than anything to see nothing more than a minor rain event from any tropical systems, but that is of course just wishful thinking. Let’s take a look, not using what I hope happens, but what I think will happen, using all of the factors I have to work with.

Current situation and models

Tropical Storm Ernesto continues to chug across the Caribbean as a moderate tropical storm with winds of about 50 mph. This is due to a strong subtropical ridge to the north creating this kind of steering flow. This ridge is forecast to weaken with the passage of a trough to the north. However, Ernesto is likely to not be close enough to the weakness to head significantly to the north, and the ridge will likely fill a bit after the trough passes. The storm is slowing down a bit as it approaches the coast of Honduras, and may slow down some more before reaching the Yucatan. Ernesto has also been battling a lot of dry air and some lower-level shear while in the Caribbean, curtailing intensification. In fact, some pro mets even suspect Ernesto may have de-generated into a tropical wave as of today. However, Ernesto has gotten better organized in the last few hours, and is forecast to continue to do so until landfall sometime on Tuesday. The National Hurricane Center thinks Ernesto will eke out hurricane strength when it makes landfall, at 75 mph. Then again, the official forecast also has Ernesto staying offshore of Honduras, which is definitely not a given. It will probably reach or pass just north of there on Monday evening, with the official forecast of about 60-65 mph in that area.

Ernesto will naturally weaken while over the Yucatan Peninsula. The questions are, how long will it spend over land, how much will it weaken, and how much time will it spend over the Bay of Campeche? Well, Ernesto is currently forecast to spend probably about 24 hours over land before reaching the Bay of Campeche, or emerging probably Wednesday afternoon. It is currently forecast to have maximum winds of 40 mph by the time it emerges. The Euro model has Ernesto following a path like this, but making landfall very early on Friday near Veracruz. However, the GFS has Ernesto continuing inland after landfall in Belize, and never re-emerging. Regardless, conditions appear to be more favorable in the western Gulf of Mexico and Bay of Campeche for intensification, if it makes it there. This makes predicting Ernesto a very tricky exercise. If there is one thing that must be remembered, the trend is your friend. The trend is for Ernesto’s track to keep getting shifted further to the south. No matter what, areas where this storm hits can expect very copious amounts of rain, especially if Ernesto is able to mix out some of its dry air in the western Caribbean. Ernesto appears to be trying to do just that.

Tropical Storm Florence surprised me Friday and over the weekend, but is now weakening fast. This storm is forecast to continue to weaken while heading west or west-northwest over open waters, and into an area of stronger shear and drier air. The waters in the area around Florence are also a little cooler than average, which will also hinder any chance of intensification. The double-edged sword with this is that Florence could be steered by a lower-level flow to the west, and not into any weakness in the subtropical high pressure ridge to its north. If this happens, re-development further west over warmer waters cannot be ruled out, especially if shear is lighter and the air moister. The GFS is at least giving this idea a thought and re-curving it beginning on Saturday, but this idea is not supported by the Euro model.

Lastly, by the time the weekend rolls around, the GFS is showing an interesting system coming off the African coast, but pretty far to the north, near the Cape Verde Islands. The Euro model does not seem to pick up on this system, or is at least calling for just a tropical wave for the time being. On the other hand, the GFS does also show a very significant hurricane in the very long range potentially threatening the East Coast, sometime around August 20. While I do not take much stock in these way-long range models, this disturbance coming off during the weekend would be a good candidate for following a track like that, simply given the time. Regardless of where it develops, that high pressure ridge isn’t likely to just go away anytime soon, so this system would probably keep going west. Then again, most systems that make that far west, that go that far north, take lots of time before they actually develop further.

Also, remember that 2012 is a likely El Nino year. This may have caused the unfavorable conditions that have given Ernesto and Florence problems in what may have otherwise been very favorable environments to intensify.

Recent history

Since 1960, these storms have occurred in the Caribbean during the first half of August:

Camille in 1969
Cora in 1978
Allen in 1980
A weakened Dennis in 1981
Diana in 1990
Bret in 1993
Cindy in 1993
Charley in 2004
Emily in 2011

This describes nine tropical storms, six of which were hurricanes at some point. Additionally, three of these storms peaked at category 3 or higher. However, the ones that truly took classic Caribbean paths similar to Ernesto’s would be Allen, Dennis, Diana, and Charley. All of these storms were hurricanes at some point. Allen and Charley were or became hurricanes while in the Caribbean, Diana became one after crossing into the Bay of Campeche, and Dennis re-curved to the north, but became one off the North Carolina coast on its way out to sea. Dennis was the weakest of this bunch, primarily a tropical wave as it crossed, but had been a named storm prior to then, and re-developed as it was approaching Cuba. The only storms to occur at all during this period in the Caribbean in El Nino years both happened in the same year, 1993. Bret tracked across the southern Caribbean, along the coast of South America, and struggled with intensity all throughout its journey. Meanwhile, Cindy could never get off the ground in the eastern Caribbean, topping at 45 mph before wringing itself out over Hispaniola.

Also somewhat noteworthy, though these storms occurred a little later, are Chantal in 2001, Dean in 2007, and Harvey in 2011. These storms also took more classic Caribbean paths and tried to intensify. Chantal and Harvey became respectably strong tropical storms, while Dean became another one of the classic intense hurricanes in this area. Chantal and Harvey tracked further south, with Chantal never reaching the Bay of Campeche, and Harvey only barely touching and briefly re-intensifying to a weak tropical storm.

Just in case Ernesto makes its way into the Bay of Campeche, I also want to look at storms that cross the Yucatan into the Bay of Campeche, not just right now but as a whole. Storms like this include:

Edith in 1971
Brenda in 1973
Hermine in 1980
Debby in 1988
Diana in 1990
Gert in 1993
Dolly in 1996
Keith in 2000
Gert in 2005
Stan in 2005
Marco in 2008
Alex in 2010
Karl in 2010
Arlene in 2011
Nate in 2011

Debby, Gert and Marco actually formed in the Bay of Campeche more or less, but would have followed similar paths across the Yucatan Peninsula to reach where they did to develop. This makes the full sample size 15 storms. Of this batch, ten went on to become hurricanes after emerging. However, only Karl became a category 3 storm. Alex did come close, but also took a more unusual northerly path to get to where it did. The storms that failed to become hurricanes on the way to Mexico include Edith (though it clipped the coast, re-curved northeast, and did become one anyway as it tracked that way), Hermine, Gert, and Marco, and Arlene. Arlene, Hermine and Marco had favorable conditions and became strong tropical storms with winds of 65-70 mph. Hermine and Marco simply only had about 24 hours of water to work with. Arlene had 48 hours or so, but occurred in June, when it is a bit harder to intensify markedly, and conditions were a little less favorable. Edith and Gert, meanwhile, had less favorable conditions as they crossed this body of water. Nate, which was only briefly a hurricane, had similar conditions during its time there too. On the other hand, Brenda had only about 24 hours of water to work with and managed to become a minimal hurricane anyway. But all of the other storms had about 36-48 hours or so in these warm waters – with Alex having even longer due to its unusual path, even in June (all of the others were closer to the peak of the hurricane season). Also, all of these storms that actually occurred prior to the Yucatan, spent about 24 hours over land.

Noteworthy also is Gert in 1993. Like 2012, that year was an El Nino year, and Gert hit Belize as a very minimal tropical storm and spent not quite 24 hours over land, weakening to a tropical depression. In its 48 hours before landfall near Tuxpan, it managed to strengthen all the way to a category 2 storm with winds of 100 mph. In an El Nino year. Also, Diana actually occurred around this time and emerged with winds of 45-50 mph, spent about 36-48 hours over water, and also became a category 2 hurricane before its final landfall. However, this storm and Gert are more known for their heavy rains than how intense they were at landfall.

On the other hand though, only four hurricanes in the satellite era have ever hit Mexico from the Atlantic during El Nino years: Anita in 1977, Barry in 1983, Gert in 1993, and Isidore in 2002. Only Gert hit an area where Ernesto might come close to hitting of this mini-set. Ida came close to the Yucatan in 2009 as a hurricane. The only other tropical storm to come close to Mexico in an El Nino year was weak Arlene in 1993.

Ernesto is not the only player in town however. These storms developed or occurred in the Main Development Region in the first half of August:

Arlene in 1963
Debbie in 1969
Alma in 1974
Cora in 1978
Allen in 1980
Bonnie in 1980
Dennis in 1981
Fran in 1990
Felix in 1995
Alberto in 2000
Danielle in 2004
Earl in 2004
Irene in 2005
Dean in 2007
Ana in 2009
Bill in 2009

That’s 16 total storms during this upcoming week, of which ten became hurricanes in that area. Two others – Dennis and Irene – became hurricanes further north. Only three times in the satellite area have there been instances of two storms in the first half in this area, in 1980, 2004, and 2009. Allen developed around the beginning of the period, while Bonnie came toward the dead middle of the month in 1980. Danielle actually formed first just off Africa, followed immediately by Earl closer to the Caribbean, an unusual occurrence. Both occurred toward middle of August. But in 2009, a fellow El Nino year, Ana was a weak tropical storm that fizzled out, but helped pave the way for the more intense category 4 Hurricane Bill. Both of these storms were roughly concurrent in this region around the middle of August. However, Bill is also the only storm to become a hurricane in this region after forming during this time period in an El Nino year, let alone the only major one on top of it. But there has not in the satellite era been an instance of three named storms in this area between August 1 and 15, which the GFS is trying to suggest.

So what does this all tell us?

Lots of information to be had, but that is to be expected during a busy week like this one. Ernesto will likely reach the Yucatan Peninsula sometime on Tuesday as a moderate tropical storm as it likely decelerates due to a small weakness in the high pressure ridge to its north. Specifically, it looks like Ernesto's center will probably hit Belize. The storm will weaken during its passage over land. Ernesto is forecast to weaken from 75 to 40 mph right now, which I think sounds about right... but that’s if the official forecast and the Euro model prediction both verify. The GFS, on the other hand, dissipates Ernesto over Central America, never taking it over water, similar to Tropical Storm Chantal in 2001. Regardless, conditions appear favorable in the Bay of Campeche for development, and all of the reliable that take Ernesto there do intensify it. When looking at the models as a whole and their trends, if Ernesto reaches the Bay of Campeche, he will probably make landfall somewhere near Veracruz or Tuxpan. With somewhat weaker steering currents, Ernesto will have about a decent amount of time to work with over these waters before reaching the coast on most likely Friday. This will give it ample time to intensify before reaching the coast, and it could therefore become another Diana or Gert-like storm, from the early 90's. However, hurricanes rarely hit Mexico from the Atlantic during El Nino years; it has happened only four times in the satellite era. Then again, not many storms have ever taken a track like Ernesto in El Nino years, either, especially this time of year.

On a side note, if this wasn’t an El Nino year, and conditions were more favorable in the Caribbean, could you imagine what type of storm Ernesto might be? I’m frightened to think about it, and am happy conditions were and are less favorable in this area!

Florence is weakening over the open Atlantic thanks to cooler-than-average waters, shear that is strengthening, and dry air in the atmosphere around it. However, Florence might help pave the way for another disturbance behind it in a week or so, no matter how long she lasts. I don’t think Florence will re-develop, but the GFS does at least suggest it could happen. If it does, it appears Florence would remain a very weak storm and re-curve safely out to sea. In the meantime, I am not entirely sold that we will have Gordon or even a tropical depression by the end of the week. It is simply put, very difficult to get three named storms in the Main Development Region this early in August in any year, let alone one with an El Nino. There will be a vigorous tropical wave however, and this may develop further down the road as it progresses westward underneath the ridge of high pressure to the north.

The prediction

And now it’s time for the main event. I’m sure I’ve kind of hashed what could happen. Ernesto is simply going to be a very difficult storm to predict. So what will happen, in my opinion? I’ll break each system down individually.

I predict Tropical Storm Ernesto to continue toward the west to west-northwest, but slowing down in forward speed on Monday and begin to dump some localized heavy rains in Honduras that day while the center clips the coast with winds of 50-60 mph. Ernesto will then briefly re-emerge over the Gulf of Honduras, but make landfall in Belize on Tuesday afternoon or evening with winds of about 60-70 mph, failing to become a hurricane as I think conditions still aren’t quite entirely favorable, and it will be a bit too close to Honduras and some of its higher mountains. Heavy rains will spread over the Yucatan during Ernesto’s passage over land, and into Guatemala as well. Ernesto will not reach the Bay of Campeche, and continue heading west just inland. By Thursday morning, Ernesto will weaken to a tropical depression in eastern Mexico, and dissipate by the next day. Confidence is 60%. However, please remember that this is an amateur opinion, and should NOT be treated as an official forecast. Listen more to the official forecasts and your governmental and local authorities for what to do should this potentially dangerous storm threaten your area. If Ernesto reaches the Bay of Campeche, it could get quite a bit more intense than I predicting, potentially reaching hurricane intensity. Thank you.

I know with this prediction of Ernesto not reaching the Bay of Campeche, that that would seem to make discussion of what would happen there irrelevant. I think it is very much relevant though, as the uncertainty with this storm is so high at this point.

I predict Tropical Storm Florence to continue to weaken on Monday to a tropical depression, and then a remnant low that night as it continues to swirl harmlessly over the open waters of the Atlantic. I also predict no re-development later on down the road for Florence as the remnant low continues west-northwest, passing a fairly safe distance north of the Lesser Antilles, Virgin Islands, and Puerto Rico on Friday and then northwest from there over the weekend. Confidence is 70%.

Elsewhere, I predict no tropical development this upcoming weekend behind Tropical Storm Florence during the weekend, or anywhere in the Atlantic this upcoming week. Confidence is 70%.

As a last aside, I think I saw models are developing a system in the Eastern Pacific a bit later this week, off the coast of Mexico. It would not surprise me if Ernesto’s remnants made it that far and eventually became Gilma or Hector, depending on how much further Invest 92E develops.

-Andrew92

[Andrew92]

And it's time to evaluate.

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.

-Andrew92

[rainstorm]

you did your best. its all we can ask