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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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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000
WTNT41 KNHC 280241
TCDAT1
TROPICAL STORM ALEX DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010
1000 PM CDT SUN JUN 27 2010

AN AIR FORCE RESERVE UNIT AIRCRAFT HAS BEEN INVESTIGATING ALEX THIS
EVENING AND MEASURED A MINIMUM PRESSURE OF 991 MB AND PEAK
FLIGHT-LEVEL WINDS OF 42 KT NORTH OF THE CENTER. THE PLANE ALSO
MEASURED PEAK SFMR WINDS OF 41 KT TO THE NORTH OF THE CENTER.
SATELLITE IMAGES INDICATE THAT CENTRAL CONVECTION IS REFORMING...
BANDING FEATURES ARE GRADUALLY INCREASING...AND UPPER-LEVEL OUTFLOW
IS WELL-ESTABLISHED IN ALL QUADRANTS EXCEPT THE NORTHWEST. BASED
UPON THE AIRCRAFT MEASUREMENTS AND THE INCREASED ORGANIZATION ON
SATELLITE IMAGES...ALEX IS ONCE AGAIN UPGRADED TO A TROPICAL
STORM...AND THE ADVISORY INTENSITY IS SET AT 40 KT.

ALTHOUGH THE 12-HR AVERAGE INITIAL MOTION ESTIMATE IS 300/6...
SHORTER-TERM FIXES SUGGEST THAT ALEX MAY BE MOVING EVEN SLOWER.
DURING THE FORECAST PERIOD...GLOBAL MODELS FORECAST AN UNUSUALLY
DEEP LONGWAVE TROUGH TO DEVELOP OVER THE NORTHEASTERN UNITED STATES
WHICH SHOULD RESULT IN A TEMPORARY WEAKENING OF MID-LEVEL RIDGING
ALONG THE NORTHERN GULF COAST. THE GFS/CANADIAN MODELS CONTINUE TO
INDICATE A WEAKER VERSION OF THE MID-LEVEL RIDGE AND HENCE A MORE
NORTHWESTERLY OR NORTH-NORTHWESTERLY MOTION...WHILE THE ECMWF/
UKMET/NOGAPS HAVE CONSISTENTLY PREDICTED A STRONGER RIDGE AND MOVE
ALEX ON A MORE WEST-NORTHWESTERLY COURSE. THE OFFICIAL NEW FORECAST
IS QUITE SIMILAR TO THE PREVIOUS ADVISORY...AND CLOSELY FOLLOWS A
CONSENSUS OF THE DYNAMICAL MODELS THAT EXCLUDES THE GFS...SINCE THE
LATTER MODEL APPEARS TO BE SOMEWHAT OF A NORTHERN OUTLIER AT THIS
TIME.


NOW THAT THE CENTER OF ALEX HAS EMERGED OVER THE GULF OF
MEXICO...GLOBAL MODELS PREDICT AN ENVIRONMENT CHARACTERIZED BY
LIGHT VERTICAL WIND SHEAR AS ALEX MOVES OVER WARM WATERS. BOTH OF
THESE INGREDIENTS SHOULD FAVOR STEADY INTENSIFICATION
UNTIL LANDFALL. PERHAPS THE ONE NEGATIVE FACTOR IS THE LARGE SIZE
OF THE CIRCULATION...AS IT MAY TAKE SOME TIME FOR THE CYCLONE TO
CONSOLIDATE FURTHER. GIVEN THE FAVORABLE LARGE-SCALE CONDITIONS...
IT IS STILL PUZZLING THAT THE GFDL/HWRF DO NOT SHOW ALEX
STRENGTHENING TO MORE THAN A TROPICAL STORM DURING THE NEXT SEVERAL
DAYS. STATISTICAL GUIDANCE...ON THE OTHER HAND...CONTINUES TO
FORECAST A STRONGER TROPICAL CYCLONE AND THE NHC INTENSITY FORECAST
REMAINS CLOSE TO SHIPS/LGEM MODEL OUTPUT. IN ANY EVENT...IT SHOULD
BE NOTED THAT THE SKILL OF 2 TO 3-DAY INTENSITY FORECASTS IS VERY
LOW.
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stalls it where?
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QPF Day 3 Thurs July 1.

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3084. xcool
GFS 00z stallsAlex
Member Since: September 26, 2009 Posts: 2 Comments: 15603
Quoting tennisgirl08:
Let's say that Alex stalls until the ridge breaks down as the trough rolls in. The next move would be North. Then the question remains that the ridge would then build back in. This is what the GFS is showing. I think we are at a critical moment here in seeing which models are correct. The next real movement from Alex will tell.


I SO agree tennisgirl..:)
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Quoting ElConando:
Curious, any regular bloggers that live on Mexico here?


Hi! Here I am as you requested :) I'm from Monterrey in Northeastern Mexico, about 180 miles east of Brownsville.

And by the way, I'm sticking with the forecast that the cmc and bamm models gave since last week with the ridge building west enough for the system to make a landfall between La Pesca and Matamoros.

Actually the current NHC track brings the t.d. just south of the city!
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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?
Member Since: August 22, 2006 Posts: 10 Comments: 414
GFS 00z Look similar to 18Z
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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.
Its just a large storm so there is a looser pressure gradient.
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3078. Patrap
..I iz befuddled
Member Since: July 3, 2005 Posts: 415 Comments: 125628
Drak why is GFS so gunho on the northerly track so consistanly now
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Quoting Drakoen:
GFS 00z takes Alex into central Texas



Link plz Drakoen?? Thanks..:) And hello BTW..:)
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Let's say that Alex stalls until the ridge breaks down as the trough rolls in. The next move would be North. Then the question remains that the ridge would then build back in. This is what the GFS is showing. I think we are at a critical moment here in seeing which models are correct. The next real movement from Alex will tell.
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GFS is sure persistant on a northerly track, makes you wonder
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3072. xcool
RitaEvac LOL
Member Since: September 26, 2009 Posts: 2 Comments: 15603
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3070. Drakoen
GFS 00z takes Alex into central Texas
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BP told me dont worry about that, taking the time to do that costs money, just go on out there and get that job done
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3068. will45
looks like you unbroke it SJ lol
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3066. Patrap
Quoting RitaEvac:
Pat, gonna go check on those crackers out there


Wear a Hard hat
Member Since: July 3, 2005 Posts: 415 Comments: 125628
3065. Patrap
Member Since: July 3, 2005 Posts: 415 Comments: 125628
Pat, gonna go check on those crackers out there
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Quoting Drakoen:


It's going to take time for the winds to catch up now that the center is off shore


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.
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Quoting pipelines:


There seems to be a lot of confusion about the pressure of Alex and his current wind speed, there is also a lot of speculation that his wind speed will be drastically increasing in the next few hours, let me explain.

Systems as large as Alex typically have lower pressures for given wind speeds but they span over a greater area. This is due to the fact that pressure influences wind speed, pressure doesn't create windspeed. Windspeed is created by pressure changes, or pressure gradients. A large system like Alex or Ike will drop the pressure over a much larger area. Because the pressure is lower over such a large area, the pressure gradient near the center of the system is less. If Alex was half the size it currently is and at the same pressure, there is no doubt the windspeed would easily be in the 60-70 mph range. Remember, the change in pressure over a given area creates windspeed, not the pressure itself.


Ah..thanks! That does make sense.
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Quoting LSU791:

If I remember correctly Dr. Masters was quoted on here earlier saying that residents in Louisiana should make preps. in anticipation of a hurricane landfall by Weds. By my math that is only 3 days from now.


Thats right LSU791 :)
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Curious, any regular bloggers that live on Mexico here?
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3059. Patrap
Member Since: July 3, 2005 Posts: 415 Comments: 125628
did the models predict this stall?
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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.
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3056. xcool
TampaSpin :(
Member Since: September 26, 2009 Posts: 2 Comments: 15603
3055. reid221
Quoting aspectre:
2991 leu2500 "Companies do not have to rely on the NOAA/NHC. Many hire private forecasters."

And where do those forecasters get their information from??? NOAA and the NHC maybe?


The amount of information available for forecasters is incredible. I have bookmarked dozens of links that have been shared on this blog over the years.
Many universities (especially FSU and CO) have elite meteorological departments .. Buoy data - ship reports .. I know for a fact that many corporations have teams that form their own independent forecasts with no regard for the opinions of the NHC or NOAA.
While we debate here .. the facts are that the best scientists in the world with super computers and a lifetime of experience cannot agree on track or intensity ..
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guys in Gulf at wellhead will be screwed if it went north anyway, they would have to be gone right now, 5 days in advance my butt,
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Quoting ElConando:
People in LA should keep keep tabs on it but I wouldn't worry too much about a yet esp since anything hitting there would be 6 days away.


My current thinking is that Louisiana is completely in the clear, at least in terms of a landfall occurring there.
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Quoting tennisgirl08:
Hey Miami and Drak! Alex looks to be stationary due to weak steering currents and ULL pushing down on it. So, what's his next move? Will it be the trough steering it? The reason I ask...wouldn't that warrant a drastic change in the forecast cone? Also, 991mb. Is that really 45mph strength. I am so confused....LOL!


There seems to be a lot of confusion about the pressure of Alex and his current wind speed, there is also a lot of speculation that his wind speed will be drastically increasing in the next few hours, let me explain.

Systems as large as Alex typically have lower pressures for given wind speeds but they span over a greater area. This is due to the fact that pressure influences wind speed, pressure doesn't create windspeed. Windspeed is created by pressure changes, or pressure gradients. A large system like Alex or Ike will drop the pressure over a much larger area. Because the pressure is lower over such a large area, the pressure gradient near the center of the system is less. If Alex was half the size it currently is and at the same pressure, there is no doubt the windspeed would easily be in the 60-70 mph range. Remember, the change in pressure over a given area creates windspeed, not the pressure itself.
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Quoting aspectre:
3016 ElConando "Strange that the NW Yucatan isn't under TS Warning since it shows TS winds over it. No one live there?"

The people who live there already know...
...and don't want to scare away the tourists who have yet to arrive.


A possibility. Not gonna rip my hair out about it though.
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3050. LSU791
Quoting ElConando:
People in LA should keep keep tabs on it but I wouldn't worry too much about a yet esp since anything hitting there would be 6 days away.

If I remember correctly Dr. Masters was quoted on here earlier saying that residents in Louisiana should make preps. in anticipation of a hurricane landfall by Weds. By my math that is only 3 days from now.
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3032. Nothing to do with LA there.
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Quoting xcool:
TampaSpin good job you know....


Ya thanks.....got lucky i guess!
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Quoting sarahjola:
imo i think that the dip south people are seeing is not the coc. i think the coc is just north of that, and maybe it might be about to take a serious n. turn or possible nne. i am probably wrong, but that's what I'm here for. so you all can school me. thanks in advance for any info:)


You are correct on the CoC, it's actually underneath the small CDO on the North side of the system. Many people, myself included, were following a dry slot that is now clearly rotating around the CDO.

As for making a serious turn, no, i don't think so.
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Quoting aspectre:
TSAlex remains ~571hours away from the DeepwaterHorizon.

At 120hours away, personnel evacuations and shutdown procedures for ship evacuations begin.


Quote by Coast Guard Admiral Thad Allen at yesterday's press briefing

"If we get an indication that we have a chance for gale force winds at the wellhead, a 120 hours out in advance that’s when we'll make the decision."

http://www.enewspf.com/index.php/news/88888996-bpgulf-oil-spill/17257-press-briefing-by-national-in cident-commander-june-26-2010
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3044. Patrap
ATCF images (Hurricane Track Models)

Current Storms:
Alex
Member Since: July 3, 2005 Posts: 415 Comments: 125628
3033. StormJunkie thanks so much
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3016 ElConando "Strange that the NW Yucatan isn't under TS Warning since it shows TS winds over it. No one live there?"

The people who live there already know...
...and don't want to scare away the tourists who have yet to arrive.
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3041. Patrap
00z Early Cycle NHC model tracks
Alex
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)



Early Model Wind Forecasts

Member Since: July 3, 2005 Posts: 415 Comments: 125628
Quoting ElConando:
People in LA should keep keep tabs on it but I wouldn't worry too much about a hit esp since anything hitting there would be 6+ days away.


The only thing I'm worried about is that my neighbors next door are in the process of raising their house. It can't take a strong wind or it'll blow it off the blocks. And it won't be done for a few more weeks..
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Quoting matt03blueoptima:
anyone has the link to the 00z runs? i would greatly apreciate..

thanks in advance

matt


The 00z runs aren't quite out yet, but you will be able to find them on the links under models. The NWS NCEP page will have the GFS on it and that will be one of the first 00z dynamical models that start coming out.
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Broke blog?
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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.