Alex may head north to Texas or Louisiana

By: Dr. Jeff Masters , 6:36 PM GMT on June 27, 2010

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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

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3138. Levi32
Quoting shakaka:




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'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.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting gator23:
This should say everything about tropical storm forecast predictions 5 days out. Stay sharp everyone.

Link
yeah that one was pretty crazy...
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3136. will45
The weakness in the ridge may be filled back in by the time Alex gets there
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Quoting Drakoen:
The GFS is really showing this trough pulling the system. It is interesting to me that nearly all of the GFS ensemble members point in a poleward direction.



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! :)
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Quoting RitaEvac:
Cuz BP headquarters are in Houston??


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??
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3133. Patrap
hurricane2/color_lrg/latest.jpg
Member Since: July 3, 2005 Posts: 424 Comments: 128273
Quoting IMA:
Just a reminder to include your pets in your disaster preparedness plans! See Helping Animals Weather the Storms for lots of links & suggestions.

...and hi, my WU family! I miss those of y'all I don't keep up with on FB! <3


Informative blog in there.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
Clear that Alex is reinventing itself as a much smaller, but tighter storm. This might make it less susceptible to frictional forces and more mobile in the short term.
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3129. gator23
This should say everything about tropical storm forecast predictions 5 days out. Stay sharp everyone.

Link
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i dont know but its getting late and getting tired of it just sitting there off the coast, needs to move and get all this over with
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Celia's last gasp


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.
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Quoting Patrap:
It wasnt a Gnat..it was a sesame seed from the Bun.

Whoppa with cheese


I prefer Royal with cheese.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
3125. Patrap
GOES-8 WV LARGE
Member Since: July 3, 2005 Posts: 424 Comments: 128273
Quoting Drakoen:
The GFS is really showing this trough pulling the system. It is interesting to me that nearly all of the GFS ensemble members point in a poleward direction.



WHOA!! Whatta change!!! YIKES!!!!
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It seems to be alot of scenarios in play here..the question is which scenario is Alex gonna play? LOL !!
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3122. Patrap
Member Since: July 3, 2005 Posts: 424 Comments: 128273
Cuz BP headquarters are in Houston??
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3120. Drakoen
The GFS is really showing this trough pulling the system. It is interesting to me that nearly all of the GFS ensemble members point in a poleward direction.

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3119. Patrap
Quoting IMA:
Just a reminder to include your pets in your disaster preparedness plans! See Helping Animals Weather the Storms for lots of links & suggestions.

...and hi, my WU family! I miss those of y'all I don't keep up with on FB! <3


Hiya IMA..

Member Since: July 3, 2005 Posts: 424 Comments: 128273
Quoting Orcasystems:


I thought I would let it FLY, and see how it went


Yea Id like to see you WORM your way out of this one
Member Since: March 10, 2010 Posts: 1 Comments: 7685
3117. Patrap
It wasnt a Gnat..it was a sesame seed from the Bun.

Whoppa with cheese
Member Since: July 3, 2005 Posts: 424 Comments: 128273
Quoting RitaEvac:
CMC and GFS are supposed to be good models, but they ignoring them like hell


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!
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3114. IMA
Just a reminder to include your pets in your disaster preparedness plans! See Helping Animals Weather the Storms for lots of links & suggestions.

...and hi, my WU family! I miss those of y'all I don't keep up with on FB! <3
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18z GFS ensembles mean.

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Quoting Patrap:
..I iz befuddled
Me Too Pat!!!!
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)
Member Since: July 7, 2005 Posts: 6 Comments: 3261
3111. Patrap
Member Since: July 3, 2005 Posts: 424 Comments: 128273
3110. shakaka
Quoting Levi32:


Probabilities are needed for a lot of things in weather forecasting but there is no need to try to be so specific with development potential, for instance. I go with "low" "moderate" or "high" chances of development. And making a probability forecast for landfall is kind of pointless....even the NHC just goes with a cone of uncertainty. That's all I do....section of coastline that it might make landfall on.




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.
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3108. hydrus
Quoting Drakoen:


Hello

Next it will be over Pensacola. jk
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Quoting Comradez:
I have a theory about why the convection is firing on the west side and moving onshore, and why the center is taking its sweet time to get away from the shore:

The seabreeze effect. By mid-afternoon/early evening, the land is much warmer than the ocean (the land heats up faster than the water), so air rises over the land, and the dominant flow is onshore. By morning, it usually reverses -- the land cools off faster than the water, making the water warmer than the land, causing more uplift over the ocean and a flow offshore.


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.
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CMC and GFS are supposed to be good models, but they ignoring them like hell
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3105. Patrap
Quoting Drakoen:
The NHC said the GFS is a northern outlier but why didn't they include the CMC whose track is even more poleward




Interesting tid bit
Member Since: July 3, 2005 Posts: 424 Comments: 128273
Quoting Patrap:


I think I swallowed a gnat..

Is that a bad sign ?


Only on Weds during hurricane season and you have to have said "Who Dat" in the last 48 hours prior to swallowing said gnat.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
00z GFS

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Quoting Hurricanes101:


wow that was really bad


I thought I would let it FLY, and see how it went
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3100. Drakoen
The NHC said the GFS is a northern outlier but why didn't they include the CMC whose track is even more poleward
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Quoting Orcasystems:


Depends... does it BUG you?


wow that was really bad
Member Since: March 10, 2010 Posts: 1 Comments: 7685
Not buying that track Drak, too far north
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Quoting Patrap:


I think I swallowed a gnat..

Is that a bad sign ?


Depends... does it BUG you?
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3096. Drakoen
Quoting Joanie38:



Link plz Drakoen?? Thanks..:) And hello BTW..:)


Hello

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3095. Patrap
Quoting ElConando:


Why so?


I think I swallowed a gnat..

Is that a bad sign ?
Member Since: July 3, 2005 Posts: 424 Comments: 128273
3094. Drakoen
Quoting pipelines:


I disagree drak, while we may see a slight increase even if Alex doesn't strengthen, I don't think it will be much. Flight level winds would be much higher than surface level winds if land friction was the primary factor in the lower wind speeds we're seeing at the moment.


Maybe but the system pressure has been decreasing as it moved off-shore and we could easily see those surface winds start to pick up more significantly now that the system is over water. Over a 6 hour period the pressure went from 998mb to 991mb.
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Quoting Patrap:
..I iz befuddled


edit: oh about the storms future. You are one of many.
Member Since: September 6, 2009 Posts: 2 Comments: 3720
Quoting Drakoen:
GFS 00z takes Alex into central Texas


Great to see you back.

The GFS looks a bit too north.
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Quoting Dropsonde:
OK, 00Z GFS is sticking to its guns. I am reminded of a game of chicken. I wonder who's going to back off, GFS & Co. or ECMWF & Co., and when it will happen?


LOL! and those are the real party lines. I think that I am going to vote for GFS.
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Hey Drak it only shows it out 78 hours the last one stalled it near the S Texas coast also
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Quoting Comradez:
I have a theory about why the convection is firing on the west side and moving onshore, and why the center is taking its sweet time to get away from the shore:

The seabreeze effect. By mid-afternoon/early evening, the land is much warmer than the ocean (the land heats up faster than the water), so air rises over the land, and the dominant flow is onshore. By morning, it usually reverses -- the land cools off faster than the water, making the water warmer than the land, causing more uplift over the ocean and a flow offshore.


Interesting explanation for the place, where it hung up a bit. However, how long would you expect this to last? The effect would neutralize and then reverse in most locations, before sunup.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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