Alex may head north to Texas or Louisiana
Tropical Depression Alex has held together fairly well during its passage over Mexico's Yucatan Peninsula, and stands poised to re-intensify back into a tropical storm once it emerges from the coast tonight. Alex brought heavy rains to northern Honduras, Mexico's Yucatan Peninsula, and Belize over the weekend. It was not a good beach day in Cozumel yesterday, as 9.25" of rain fell. Cancun received 2.05" over the weekend, and Belize City received 4.57". Satellite loops show that Alex's heavy thunderstorms are mostly gone near the center, though there are some impressive bands of precipitation well away from the center. There is an upper-level high pressure system a few hundred miles west of Alex, and the clockwise flow air around this high is bringing upper-level winds out of the northwest of about 5 knots over the storm, contributing to the 5 knots of wind shear observed in this afternoon's wind shear analysis from the University of Wisconsin's CIMSS group. Sea Surface Temperatures are very warm, 29 - 30°C, and dry air is currently not a problem for Alex.
Figure 1. Afternoon satellite image of Alex.
Forecast for Alex: which model should you trust?
While the track forecast for Alex today through Monday is fairly well-assured, the longer range forecast has become highly uncertain. An increasing number of our reliable models are now indicating Alex may take a more northerly track beginning on Tuesday, with possible landfall on the Texas coast near Galveston on Friday (according to the 8am run of the GFS model) or into western Louisiana on Wednesday (the 8am run of the Canadian model.) The key question remains how Alex will react to the trough of low pressure expected to swing down over the Eastern U.S. on Monday and Tuesday. Most of the models were predicting that the trough would not be strong enough to swing Alex to the north, and several of them continue to predict this. The 8am runs of the NOGAPS and ECMWF models, for example, take Alex into the Gulf coast of Mexico 150 miles south of Texas, on Wednesday. The GFDL and HWRF models split the difference, with the GFDL predicting a Thursday landfall in southern Texas near Brownsville, and the HWRF predicting a Thursday landfall near Corpus Christi. Morris Bender of the GFDL group has just provided me the track forecast from an improved experimental version of the GFDL that shows landfall between Corpus Christi and Galveston. So which model should you trust? Last year, the best performing models at the 3 - 4 day forecast range were the GFS and the Canadian, and these are the models that are currently calling for the more northerly track towards the upper Texas coast and Louisiana. Residents of those areas should review their hurricane preparedness plans and anticipate that Alex could make landfall as early as Wednesday in their vicinity. Residents of the Mexican coast south of Brownsville should make similar plans, as Alex could just as easily hit there.
Re-intensification of Alex is likely once the center of Alex moves offshore, though this will initially be slow due to the current disorganized state of the storm and the relatively low total ocean heat content in the 100-mile-wide stretch of water on the west side of the Yucatan Peninsula. Once Alex moves more than 100 miles from the Yucatan, total heat content of the ocean increases substantially, and Alex will have the opportunity to intensify significantly. A longer time spent over water will give Alex more of a chance to strengthen, and it is possible Alex could intensify into a major hurricane if landfall is delayed until Thursday or Friday. However, Alex's intensification may be limited the farther north it gets, as water vapor satellite images show plenty of dry air over Texas that might interfere with development. Wind shear might also be an issue for Alex if it pushes far enough north, and a slow-moving storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are plenty of roadblocks that make this only a 10% probability in my estimation.
Figure 2. Skill of computer model forecasts for Atlantic named storms during 2009. OFCL=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; NOGAPS=Navy Operational Global Prediction System model; UKMET+United Kingdom Met Office model; ECMWF=European Center for Medium Range Weather Forecasting model; CMC=Canadian GEM model; TVCN=one of the consensus models that lends together all (or most) of the above models; BAMM=Beta and Advection Model (Medium Layer.) Image credit: National Hurricane Center 2009 verification report.
Elsewhere in the tropics
A tropical wave (Invest 94L) a few hundred miles north of the northernmost Lesser Antilles Islands has been pretty much torn apart, and is no longer a threat to develop.
Next post
Wunderground's severe weather expert Dr. Rob Carver will likely be posting an update on Alex late tonight. My next update will be Monday by 10am EDT.
Jeff Masters
Reader Comments
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I thought I would let it FLY, and see how it went
AOI
AOI
AOI
Hurricane Hunter Data
TS BUSTED FORECAST ALIBI
Only on Weds during hurricane season and you have to have said "Who Dat" in the last 48 hours prior to swallowing said gnat.
Interesting tid bit
That's all true in normal situations but when you have a low pressure system at this close a proximity, that will dominate any air movement. The air flow around Alex is being almost completely controlled by his circulation, also keep in mind the land mass Alex is next to has been covered in clouds all day and most of the places have received a good amount of rain, I would be surprised if any of the land areas near the coast reached higher temperatures than the water near by all day.
The words "low", "moderate", and "high" all imply a percent probability. If you say such and such has a low chance of happening it means you expect say 0-20%. Of course I'd be guessing because, for some very strange reason, you purposely haven't defined your labels with percentages lol. But they don't really mean anything without numbers behind them. They're just words of degree purely open to interpretation.
As for the cone of uncertainty it should be fairly clear from the name that it's based solely on probability. Read the text below the cone for Alex on the NHC page. It's an overall 67% probability plot for the track with other uncertainties built in for each time point.
Anyway, none of this is really important but hopefully you can understand my confusion. Not using percentages because you don't like them, whatever that means, is kind of silly. There's really no logical reason for it.
I have to say this is the craziest Storm I have ever been a part of.... With noway of really knowing where it is going?????
Taco :o)
...and hi, my WU family! I miss those of y'all I don't keep up with on FB! <3
Makes absolutely no sense....those have been the most reliable Models year after year especially the GFS....i don't get it unless they are doing it for a purpose...i don't wanna go there at all!
Whoppa with cheese
Yea Id like to see you WORM your way out of this one
Hiya IMA..
WHOA!! Whatta change!!! YIKES!!!!
I prefer Royal with cheese.
Darby's last gasp
Alex appears almost stalled and strengthening.
Well that was my pop-in input for the day. Wish I could be here more but, life and stuff. Seems to me Alex models continue to shift north though.
Link
Informative blog in there.
good point. maybe they are ignoring the models that are bringing it closer to the spill location. by doing this, BP will stay out there longer - clean up more, contain more, and continue with the relief well drilling??
I couldn't agree more... it is definitely being persistent... but so are some of the others that take it into MX. I'll be very interested to see if any more continue to shift northward in the nxt run or two.
Not saying this is unheard of by any stretch, but if the models can't come to more of a consensus in the next 24-48 hrs, the general public (not just us WU geeks) is going to start getting very loud.
Add to it the possibility of it coming ashore at a very low angle, and it becomes reminiscent of Charlie, where a few degrees shift in track makes landfall several tens of miles north or south.
i hope the local mets begin setting that expectation soon and reminding folks of the importance of the "cone" ... esp in situations like these.
btw - i'm david. Hi everybody! i'm an avid hurricane chaser and a lurker in here for many yrs. not a met, but am a comm. pilot and weather is an uber-passion of mine. Pleasure to e-meet you! :)
I'm sure it's not logical. I just see no reason to make my posts that technical and specific. Heck....how's my mind supposed to decide whether I think Alex has a 20% chance of becoming a major hurricane or a 30% chance? Honestly....I just use general language that everyone can easily understand and get the jist of what my thoughts are on the situation.
I do see your point, and yes probabilities are essential in a lot of areas.
AH ha! They are doing it for a purpose. Finally someone is getting my drift.
MARK
19.0N/91.0W
I dont think so Coop.
Compared to the ECMWF ensembles....it is very interesting indeed. Massive model war going on here. Whichever one wins this will have bragging rights for quite a while.
Pleasure to e-meet you too!! Welcome!! :)
You're plotting it still over Mexico?
Wow! It's getting late...lol!
What timeframe does this represent?
Real-time filtering of OLR data to monitor and predict the convective variations of the Madden-Julian oscillation and various convectively coupled equatorial waves, based on the "climatological" spectral peaks of a long record of satellite-observed data.
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