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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I think Alex will make a u-turn, head all the way across the GOMEX and hit Tampa. Because, you know, we all want the big storms to hit Tampa.
:)
Member Since: Posts: Comments:
Quoting Patrap:
Bonnie
Colin
Danielle
Earl
Fiona
Gaston
Hermine
Igor
Julia
Karl
Lisa
Matthew
Nicole
Otto
Paula
Richard
Shary
Tomas
Virginie
Walter



I wonder how many names we will go through this year......
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting WaterWitch11:
Invests could be kids
LOL! Sometimes invests are cooler than tropical depressions. Remember 92L?
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Beep, if this doesn't do you in then IDk what will, viejo.

Floods not that old GW...
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good afternoon Alex =)
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Bonnie
Colin
Danielle
Earl
Fiona
Gaston
Hermine
Igor
Julia
Karl
Lisa
Matthew
Nicole
Otto
Paula
Richard
Shary
Tomas
Virginie
Walter

Member Since: July 3, 2005 Posts: 421 Comments: 127566
I don't think its going to much further north than 23.5 if that were to be the case, anyone want to speculate on the criticism for the NHC hurricane warning area.Old dammed if you do dammed if you don't.
Member Since: August 18, 2008 Posts: 0 Comments: 3112
I will stick to C, but right before landfall, Dolly did the same thing.
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It looks like Alex may finally have an eye (albeit ragged and cloud obscured)!



Member Since: August 2, 2006 Posts: 46 Comments: 11666
Invests could be kids
Member Since: August 11, 2008 Posts: 3 Comments: 1571
Quoting xcool:
TexasHurricane YEAH..


Looks like we may get a decent amount of rain.
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Cantore can take a ride to Brownsville and hang for the SPI weekend.

Woo Hooo
Member Since: July 3, 2005 Posts: 421 Comments: 127566
The way he has been all over the place I think Alex has had more than a shot or two/=. I think he sucked back the entire bottle! lol
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Quoting Snowlover123:
Poll! What do you think Alex will become?

A. Stay at Tropical Storm

B. Cat 1 Hurricane

C. Cat 2 Hurricane

D. Major Hurricane


B.
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Quoting Floodman:


A patently ridiculous statement coming from you...
LMAO!!
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting HoustonTxGal:
Can I vote A/B ?


Waht, are you high?

Sorry, sorry...couldn't help myself
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could we may be get back too Alex un less you all want a 2hr banned
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474. xcool
TexasHurricane YEAH..
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473. Daveg

Still definitely not due west, but for sure some more westerly movement in him now.

Link

Have to admit the visible is a bit more deceptive with the banding and such going on at the moment.
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Quoting ShenValleyFlyFish:


I have no gripe with you. However occasionally I have the feeling that someone did not put the screen in the window right and a misquitoe got in.


No pun intended :) .. I was just explaining my situation because the guy got lots of people on here to ignore me because he is a MET. Anyways, look at Alex, WOW.. should be a Hurricane on the next advisory.
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Looking like Alex is heading straight for the jalapeno nachos with extra cheese. He may have already had a tequila shot or two. Photobucket
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Quoting hurricanehanna:


Crow a l'organge


Quoting HoustonTxGal:
Crow al a mode ;o)


Wow, dinner AND dessert
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Quoting Snowlover123:
Poll! What do you think Alex will become?

A. Stay at Tropical Storm

B. Cat 1 Hurricane

C. Cat 2 Hurricane

D. Major Hurricane

(B) Cat 1 90MPH winds just before landfall..
Member Since: Posts: Comments:
Quoting Snowlover123:
Poll! What do you think Alex will become?

A. Stay at Tropical Storm

B. Cat 1 Hurricane

C. Cat 2 Hurricane

D. Major Hurricane
C. Right before landfall.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Floodman:


Ahhh, crow tenderloin...my favorite!


Lightly grilled and with a Fine Cabernet..
Member Since: July 3, 2005 Posts: 421 Comments: 127566
Quoting StSimonsIslandGAGuy:


B. Lieutenant.


Lol
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Tropical Wave= Toddler
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Quoting xcool:




this is rain amount right? How much is it saying for the SE Texas area? (close to LA border)
Member Since: July 2, 2009 Posts: 0 Comments: 2811
462. IKE
IKE making landfall in SE Texas....

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Quoting ShenValleyFlyFish:


I have no gripe with you. However occasionally I have the feeling that someone did not put the screen in the window right and a misquitoe got in.
Oh, I thought you were speaking to me. Nevermind.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting StSimonsIslandGAGuy:


Depressions could be recruits ;)

Invests could be kids ;)


How about a Tropical Wave? :o
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Quoting HoustonTxGal:
nope, I never said the word chicken dance LOL

I said some call Africa and tell them to not send any "waves" untill Jeff gets back from vacation.
FYI..."call Africa" is code for "chicken dance".. LOL J/K
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Quoting GlobalWarming:
me too, ike. why is it that most people only pay attention to Fl alndfalls?


A patently ridiculous statement coming from you...
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Deleting or Modifying a post dosent remove it,or the original from the server head.


Only your view.

Thats why they have a PREVIEW button next to the POST COMMENT one.

Member Since: July 3, 2005 Posts: 421 Comments: 127566
454. xcool


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Crow al a mode ;o)
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Quoting UpperLevelLOL:
So tomorrow afternoon is the main time for development then, correct? Alex should be over the loop current eddy at that time.

Yep. And I have an important meeting scheduled. Looks like I'll miss the cyclone possibly getting to Cat2 status temporarilly. Oh, the excitement of it all. I'm getting the schpulkies just thinking about it.....
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Quoting HoustonTxGal:
Can I vote A/B ?


Sure...
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Quoting Patrap:
.."Crow Mignon"..?


Ahhh, crow tenderloin...my favorite!
Member Since: Posts: Comments:
Quoting Snowlover123:
Poll! What do you think Alex will become?

A. Stay at Tropical Storm

B. Cat 1 Hurricane

C. Cat 2 Hurricane

D. Major Hurricane


B
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Quoting MiamiHurricanes09:
All altitudes basically.

Thanks.
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Can I vote A/B ?
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445. xcool
A
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Quoting Patrap:
.."Crow Mignon"..?


Crow a l'organge
Member Since: September 5, 2007 Posts: 0 Comments: 3481

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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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