Alex building an eyewall, still not a hurricane

By: Dr. Jeff Masters , 7:34 PM GMT on June 29, 2010

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Tropical Storm Alex is slowly building an eyewall, which is now more than 50% complete, according to recent satellite imagery and microwave images (Figure 1.) Satellite loops show a slot of dry air is spiraling into the center of the storm, and until this dry slot gets closed off, Alex will not be able to intensify significantly. Alex's heavy thunderstorms and low level spiral bands continue to slowly increase, but upper-level outflow is mediocre to the north and east, and absent elsewhere. The Hurricane Hunters are in the storm and have not found any hurricane-force winds at the surface yet.


Figure 1. Microwave "radar in space" image taken at 10:11 am CDT Tuesday June 28, 2010, showing that Alex had built an eyewall a little more than 50% complete. Image credit: Navy Research Lab.

Impacts
Alex is already bringing bands of heavy rain to the coasts of Texas and Mexico, as seen on the Brownsville, Texas radar. Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Since Alex is a large storm, it will have a storm surge that will affect most of the South Texas coast. NHC is giving a 40% - 60% chance of a storm surge of at least 3 feet affecting the Brownsville area, and 10% - 30% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the South Texas coast (Figure 2.) However, Alex is now unlikely to get that strong, and the surge should be less. Flooding damage from the expected 6 - 12 inches of rain from Alex will also be a major concern, as will wind damage. The combined wind, surge, and flooding damage from 2008's Hurricane Dolly, which hit near Brownsville, were about $1.05 billion. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall. I expect Alex will be similar in its impacts to Dolly, though Alex's storm surge damage is likely to be greater. If Alex hits more than 50 miles south of the Texas border, as currently appears likely, the damage will be far less, since this region of the coast is relatively sparsely populated.


Figure 2. Maximum Water Depth (storm tide minus the elevation of the land it is passing over) computed using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. The "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of five feet above mean sea level, and the combined storm surge and tide (the "storm tide") is ten feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide, and thus shows the worst-case inundation scenarios for a mid-strength Category 2 hurricane moving WNW at 5 mph. For more information on storm surge, consult our detailed storm surge pages.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models confirm the faster movement of Alex to the coast, and residents in the affected areas now have 12 hours less to prepare for Alex's arrival than it seemed with yesterday's forecasts. Conditions will begin to deteriorate along the coast late tonight, so today is the day to finish preparations if you live near the Texas/Mexico border! The ridge that is steering Alex to the northwest is expected to strengthen today and Wednesday, which should push Alex on a more west-northwest and then westerly track on Wednesday. A few models even have Alex moving west-southwest by the time it makes landfall. The most northerly landfall location, near Brownsville, is predicted by the HWRF model.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 4am CDT (9 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 88% chance of tropical storm conditions (winds 39+ mph), 23% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

Corpus Christi, TX: 42% tropical storm, 1% hurricane.

La Pesco, MX: 37% tropical storm, 3% hurricane.

Freeport, TX: 18% tropical storm, 0% hurricane.

Tampico, MX: 14% tropical storm, 0% hurricane.

Galveston, TX: 13% tropical storm, 0% hurricane.

Intensity forecast for Alex
Alex is over a region of ocean with a warm, clockwise rotating Loop Current eddy that broke off from the Loop Current in July 2009 and moved west-southwest over the past 11 months. This eddy has moderately high total ocean heat content . Wind shear has fallen to a low 5 knots, and is projected by the SHIPS model to remain in the low range, below 10 knots, this afternoon and Wednesday. The combination of low wind shear and moderately high ocean heat content should allow Alex to intensify into a Category 1 hurricane, but time is running out for it to be a Category 2 hurricane. NHC is giving Alex a 79% chance of being a hurricane on Wednesday morning, and a 4% chance it will be a major hurricane at that time. Water vapor satellite images show the amount of dry air over the western Gulf of Mexico has decreased over the past day, though as I noted above, the dry slot wrapping into Alex's core is currently keeping the storm from closing off an eyewall. Dry air may turn out to be an increasing detriment to Alex on Wednesday as the storm approaches land. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. I don't expect Alex to stall out again, so slow motion leading to upwelling of cold water will probably not be a problem for Alex. The main issue limiting intensification will be the fact that Alex is so large, and it takes more time for a large storm to organize. Thus, I think Alex has only a 10% chance of intensifying into a major hurricane before landfall.

Elsewhere in the tropics
The last few runs of the NOGAPS model have been predicting the formation of a tropical disturbance off the coast of Nicaragua on Friday or Saturday that will move northwestward towards western Cuba. The GFS model, and the two models that use it for starting conditions, the GFDL and HWRF, are indicating the possibility that a weak extratropical storm may form along coastal Alabama this weekend. It is unlikely that such a storm would be over water long enough to transition to a tropical storm.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex's winds will not directly affect the oil slick location. However, because Alex is such a deep low pressure region, strong southeast to south winds of 10 - 20 knots will blow over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border. Alex is currently bringing swells of 3 - 4 feet to the coastal regions impacted by the oil slick, and these swells will increase to 6 - 8 feet on Wednesday. Wave heights will increase to 5 - 7 feet on Wednesday. Alex is expected to bring a storm surge of 1 - 2 feet along the coast in the oil spill region. The swells and waves that will accompany these high water levels will act to push oil deep into the marshlands in some locations. The long range forecast for the oil slick region is uncertain, due to the possibility a weak area of low pressure might develop late this week along the remains of a cold front draped across the region.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Alex
2) A look ahead at what may happen the rest of hurricane season

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update Wednesday morning by 9:30am CDT. Rob Carver is planning on doing a late-night update tonight.

Jeff Masters

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Quoting MiamiHurricanes09:
True. Could just be in the process of developing a more-defined eyewall and eye, although I doubt it. Like you said, could also be dry air intrusion although it is not signified on water vapor imagery.

Forgive my ignorance, but what altitude is water vapor measured? Or is it across all altitudes?
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Quoting IKE:


Rather hectic. I don't remember you being on here then. Maybe you had been banned.


As I recall, you were trying to welcome "junior" there for a little while. ;)

I also remember all those people going on and on about how strong storms like Ike just don't go west. No way it will hit Texas. It will recurve...
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting MiamiHurricanes09:
True. Could just be in the process of developing a more-defined eyewall and eye, although I doubt it. Like you said, could also be dry air intrusion although it is not signified on water vapor imagery.


It might be behind, if you watch the loop you can see the dry air cutting through the CDO, but you see the slot start to cut through about 2 to 3 frames earlier on the vis. As the clouds release their moisture and become dry you can see them get shorter, but the moisture might still be able to be seen on the WV.
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Quoting ShenValleyFlyFish:


If someone responded to you like that you'd be crying in the corner that folks were picking on the little kid.
Terrible attempt at humor. Poof.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting KatyTX:


Allison was a Tropical Storm (not a Hurricane) and it was barely that... problem was it liked Houston soo much it decided to stay awhile. 22" of rain where I lived.

I believe they are referencing the 1995 Hurricane Allison, which made landfall in the eastern Gulf and not the Infamous 2001 Tropical Storm Allison or even the Retro 1989 version of Tropical Storm Allison, both which looped around Houston and caused deluges there.

Interesting fact: Allison was the name that replaced Alicia, which was a major hurricane that made landfall in the Houston area in 1983!
Member Since: August 2, 2006 Posts: 45 Comments: 11556
Quoting ShenValleyFlyFish:


If someone responded to you like that you'd be crying in the corner that folks were picking on the little kid.


Ahemm.. I'm 21, songwriter, in college... I've got off the deep end in past years on this blog but was never banned, I know when to keep my cool which is why I deleted that one post earlier this afternoon.
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Quoting tkeith:
lol...you do have a way with words Flood :)


Thanks, keith!

You know, I'm a very patient man and I promised the old GlobalWarming 2 years ago (he was a three letter acronym back then and I think it should be apparent to whom I am referring) that I would never **poof** him, but there's only so much sycophantish behaviour I can stand...nothuing would make me happier than to dust off the pillory
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Quoting Patrap:

TS Allison 2001 remains the only TS to have its name retired



yes, I remember her...
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting StSimonsIslandGAGuy:
I guess if Cat 3 is a major then

Cat 4 is a colonel

Cat 5 would be a general.


First time I've smiled all day. Thanks!
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Quoting StSimonsIslandGAGuy:


Cat 1 would be a lieutenant.

Cat 2 would be a captain.



LOL, SSI, I think you created a new meme. We may be talking about "Lieutenant Alex" soon, lol. Hopefully he won't get any further promotions before he retires from the service.
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Quoting Patrap:


TS Allison 2001 remains the only TS to have its name retired


TS Allison is the one that came across the US from the Atlantic right? see, I always get those 2 confused...
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Quoting VAbeachhurricanes:


I know, but you can see it, look at the RGB loop, what else besides dry air would cause the slot from the center that follows around all the way to the outside of the storm?
True. Could just be in the process of developing a more-defined eyewall and eye, although I doubt it. Like you said, could also be dry air intrusion although it is not signified on water vapor imagery.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
378. IKE
Quoting GlobalWarming:
Ike, do you recall the behavior on here, the afternoon that the NHC showed Ike hitting SF as a cat 4?


Rather hectic. I don't remember you being on here then. Maybe you had been banned.
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Congrats to the NHC for nailing another one!!! The cone never shifted much and actually almost went back to where it started. These are the experts and that is why we have them. The G-IV data also makes the forecasting these days so much easier. I do have to say the EURO did well with consistency in the latter part after it quit showing landfall in LA. The GFDL did well with intensity. Even the NHC wasn't sounding too sold on the intensity forecast with the GFDL. It all makes sense now that we have a dried up snake of a storm. I will be watching both of those models with great interest this year.
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Quoting MiamiHurricanes09:
Wow. I'm impressed. Great call Reed!


If someone responded to you like that you'd be crying in the corner that folks were picking on the little kid.
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Quoting KatyTX:


Allison was a Tropical Storm (not a Hurricane) and it was barely that... problem was it liked Houston soo much it decided to stay awhile. 22" of rain where I lived.


That's a different Allison. :)

Allison was, interestingly, the name that replaced Alicia.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
i dont know how to quote other people sorry
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TS Allison 2001 remains the only TS to have its name retired

Member Since: July 3, 2005 Posts: 414 Comments: 125530
371. IKE
Quoting hurricanejunky:


look at the map scale on the NHC 5 day cone graphic, it's about 80.


I agree with you. Looks like it comes in about 24.5N and Brownsville is at 26N.....IF it goes exactly where the NHC has it crossing.
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Hurricane Allison- June 1995
TS Allison- June 2001

Those 2 always confuse me
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Quoting GlobalWarming:


No, I do not! What about the storm that the Nogaps was forming, thoughts?


one word:

Oblivious
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Good evening! I can't believe that the NHC did not upgrade this to a hurricane. Seriously? 981 mb Tropical Storms with eyewalls? You have to be kidding me.
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Quoting Floodman:
Quoting GlobalWarming:
Texas dodged a bullet, and the NHC, once again, has been proven' impeccably accurate, like always, right, Ike? Remember the wishcasters saying that Alex was either heading up towards TX or LA? What a joke. Anyways, next, right, Ike?


You know, if Ike were to stop suddenly you'd disappear completely...you're practically an artiste!
lol...you do have a way with words Flood :)
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Quoting reedzone:


Thanks, my current forecast has it hitting the borderline of TX,MX. This however could change, but a NW motion continues, until I see a more WNW motion, and not jogs, I will keep my forecast the same.


Your forecasts have been great! Nice work on the graphics too.
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Either way.. I'm out.. hungry and going to go buy a camera... Watch out for residual moister those in Texas... Floods are too easy to come by int hat state....
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Quoting MiamiHurricanes09:
What do you use for making the graphics? I might start making a few. Lol.


Believe it or not... Paint ;)

I take the maps, copy and paste them on to paint and work my stuff.
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Quoting MiamiHurricanes09:
You look for dry air on water vapor, not RGB or visible.


I know, but you can see it, look at the RGB loop, what else besides dry air would cause the slot from the center that follows around all the way to the outside of the storm?
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Quoting Floodman:


Ahhh, the shaman has arrived!
Hey Floodman...I think HoustonTxGal requested a "chicken dance" to send Africa a message to stop with the waves. ha ha ha...
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Quoting reedzone:


Thanks, my current forecast has it hitting the borderline of TX,MX. This however could change, but a NW motion continues, until I see a more WNW motion, and not jogs, I will keep my forecast the same.
What do you use for making the graphics? I might start making a few. Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
that would make cat 1 a leutinent and cat 2 a captain!
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Quoting mtyweatherfan90:
Correct me if I'm wrong, but this would/should be the first June hurricane since 1995? With Hurricane Allison.



Allison was a Tropical Storm (not a Hurricane) and it was barely that... problem was it liked Houston soo much it decided to stay awhile. 22" of rain where I lived.
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Or the old mosquito coils....Link
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354. Daveg
Quoting Hurricanes101:
This is what happens when people watch frame by frame and do not take the overall movement of a storm over a longer period of time

anyway I will be back later when recon is out


I'm not watching "frame by frame" and I NEVER said I was. I just said in the last couple of frames.

I'm watching hours worth of sat data, thank you very much.
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Quoting VAbeachhurricanes:


you can see it on the vis and RGB, that little slot makes its way from the center all the way to the outside of the storm
You look for dry air on water vapor, not RGB or visible.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
lol!!
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Quoting btwntx08:

not 80 still like 50 mi


look at the map scale on the NHC 5 day cone graphic, it's about 80.
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Here we go, I have a bad feeling about RI during the next 12hrs.
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Quoting yonzabam:
Isn't it the case that the path of hurricanes can be influenced by mountainous terrain?

The huge outer bands of Alex will soon be interacting with Mexico's high Sierra Madre mountain range.

If, as expected, Alex approaches Mexico travelling NW, might the interaction with the mountains not push it in a more northerly direction?


Not generally how it works...the mountains will tend to oile up the bands and then shred them
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I was walking past the mental hospital the other day,and all the patients were shouting ,'13....13....13'
The fence was too high to see over, but I saw a little gap in the planks and looked through to see what was going on.

Somebody poked me in the EYE with a stick.

Then they all started shouting '14....14....14'...


had to post, for those who have already seen it, what can i say it's funny!
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Quoting IKE:


You call?


"Ike" dunno? a bunch?
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346. IKE
Quoting GlobalWarming:
Ike, do you recall Ike from 08?


Always. A classic storm/son.
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Quoting VAbeachhurricanes:


dry air infiltrating the center
What's with the dry air thing... there is little to no dry air even in the vicinity of this storm. Conditions are nearly optimal for strengthening.
Member Since: August 12, 2009 Posts: 0 Comments: 203
344. IKE
Quoting HoustonTxGal:
Ike, I think the top graphic is more harmful for us...LOL Alex blows right on by.. the sticky buns stick to the rear end FOREVER!!


LOL.
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Quoting IKE:
Alex looks like a pecan swirl....




LOL! Yes he does. Yummy!
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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.

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