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 IKE:
Spurious low(?), on the 18Z GFS @ 78 hours in the northern GOM/GOO....



Man, I love a good spurious low
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Quoting Levi32:
The Euro has bragging rights for quite a while now.....proving here that it is still king in the Atlantic.


not to be a storm specific model, it has done well.
but on the other hand Alex still has not made landfall
quite yet,but im not expecting any further surprizes.
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641. Remek
Unless there's a big jog to the North, it looks to be headed to landfall somewhere 100 miles or so South of Brownsville.

Really fascinating development today, with the spiral bands and the central development into a possible eye (finally).
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Quoting hydrus:
........................Looks like an eye in there.

hydrus... come on... you know you want to say it...

"I see a pin...."
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639. IKE
Quoting jaevortex:


Hey IKE didn't you show a model showing a low a few days ago off the coast of Alabama? Like the one that Dr. M is talking about? Link or pic if you will please?


Must to have been the GFDL. It's tied in with the GFS. It still shows a low on the 1Z run, although not as strong.
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Come on I said Northern Mexico days ago, talk about getting lucky! :)
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Quoting Capeskies:
Where can you get the EURO. I can't seem to find it. Does anyone have a link?

ECMWF
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Quoting IKE:
Spurious low(?), on the 18Z GFS @ 78 hours in the northern GOM/GOO....



Yesterday one run of the GFS stalled this offshoot of Alex for 9 days over NOLA.
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Quoting will45:


Ummmmmmmmmm i been saying for days that he would never make it to the weakness. The stall he had yesterday blew his only chance to go north
Yup. If he would of actually moved yesterday at the clip he is going now, a Texas landfall will be much more likely than a Mexico landfall. Amazing how quickly weather changes.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
........................Looks like an eye in there.
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First storm of the season

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My first forecast for Alex, maybe it was right all along..

Photobucket
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Quoting Floodman:


The early start to the wave train and the intensity of the features exiting the caost are very reminiscent of 04 and 05


You just had to bring that up, didn't you.
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629. Daveg
Quoting Levi32:
Alex is now under full influence of the ridge and is getting jammed west right into Mexico....no chance of a Texas landfall.


I tend to agree, but then again, it's dangerous to say "no chance" at all when it comes to tropical systems. IMHO.
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Quoting gator23:

Tampa sucks IMO (the guy not the city) GEESH
LMAO! SHESH. JUST SAYIN!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Where can you get the EURO. I can't seem to find it. Does anyone have a link?
Member Since: January 24, 2010 Posts: 0 Comments: 27
Quoting HurricaneSwirl:


You only have a 5-10% chance of TS force wind:


You have a 0% chance of 50 kt+ wind:


And you have a 0% chance of hurricane force wind:


Holy cow you are terrible at detecting trolls
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Quoting Levi32:
Most of our forecasts here, including mine, are now too far north. Even the NHC will likely have to shift south yet again.


Ummmmmmmmmm i been saying for days that he would never make it to the weakness. The stall he had yesterday blew his only chance to go north
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Quoting IKE:
Spurious low(?), on the 18Z GFS @ 78 hours in the northern GOM/GOO....



Hey IKE didn't you show a model showing a low a few days ago off the coast of Alabama? Like the one that Dr. M is talking about? Link or pic if you will please?
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Quoting GlobalWarming:
levi, evening


Evening.
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.
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Quoting Levi32:
Guess what guys.....ECMWF absolutely nailed this storm. Major cudos to that model in the face of the big-hitter GFS and CMC ensembles completely disagreeing with it for all this time, and now we have a clear winner. ECMWF was stellar and solid from the moment it shifted all the way west many many days ago, and despite being the southern-most outlier, it won out, clear-cut.


Best models for 2010 storms
Alex = EURO
Bonnie = ??
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Quoting Levi32:
Most of our forecasts here, including mine, are now too far north. Even the NHC will likely have to shift south yet again.
I was thinking Brownsville, but now I'm thinking further south. Like around 24N-25N.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Alex is now under full influence of the ridge and is getting jammed west right into Mexico....no chance of a Texas landfall.
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615. IKE
Spurious low(?), on the 18Z GFS @ 78 hours in the northern GOM/GOO....

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Quoting MiamiHurricanes09:
I'm 100% Joe Basterdi didn't say a CAT 3 was going to hit Galveston. (Like TampaSpin would say) JUST SAYIN. Lol.


Bastardi. and why slam Tampa like that?
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613. IMA
♫ Rain to the left of me, rain to the right
Here I am, stuck in the middle again ♫

(though I'm sure not for too long)

San Antonio Radar
- click for larger image


Regional Radar shows a wet TX already - click for larger image


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Quoting earthlydragonfly:


Yes, It it interesting the appearant amount of energy (cloud cold tops) in the next wave that is about to emerge off the coast. Looks like it could be a bugger.


The early start to the wave train and the intensity of the features exiting the caost are very reminiscent of 04 and 05
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Trof lifting out and ridging coming it....Alex not going with the solution as the GFS/CMC had a few days ago.

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Most of our forecasts here, including mine, are now too far north. Even the NHC will likely have to shift south yet again.
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Quoting AstroHurricane001:


Wow. I have NEVER seen a hurricane before that took up the entire Gulf of Mexico. The convection almost stops at the coast but its outer bands are too wide to do that. That means all the dry air over Texas is gone, but Alex has not yet absorbed ex-94L. This storm is going to alter the circulation patterns across the entire Western Hemisphere. If this storm stalls, even on land, terrible flooding could result. It's only the first storm of the season, and even a category one of this size could be devastating.

Meanwhile, flooding in Southern China leaves 382 dead. Link


And your not seeing that now. Alex is still a Tropical Storm unless i missed something...
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Quoting galvestonhurricane:


That's not fair... I am very serious.


Follow that the NHC is saying then. I don't think Bastardi is that dumb
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I will be very surprised if Alex does not become a hurricane today.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
The Euro has bragging rights for quite a while now.....proving here that it is still king in the Atlantic.
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Quoting GlobalWarming:


what does that mean?

It means there is some turning of the atmosphere at 850 mb (about a mile up). This may or may not be reflected at the surface. Could be a disturbance. Could be our next storm. Could be nothing. Still a long way out.
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Quoting Levi32:
Guess what guys.....ECMWF absolutely nailed this storm. Major cudos to that model in the face of the big-hitter GFS and CMC ensembles completely disagreeing with it for all this time, and now we have a clear winner. ECMWF was stellar and solid from the moment it shifted all the way west many many days ago, and despite being the southern-most outlier, it won out, clear-cut.
Amazing model.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
I Guess Alex just likes being a TS. Sooner or later
though he's gonna have to come out of the closet!
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Quoting jaevortex:


I think this guy is trying to get to you MH, just ignore him.


That's not fair... I am very serious.
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ok flood are you being a smart alec? just thought i'd post name origin. old names are cool!
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Quoting skepticall2:


The quote you quoted didn't say Alex it said a storm. Still crazy thought as it is hard to predict it 8 days out much less at the beginning of the season or now and we didn't get a link with it so it sounds fake to me.
I'm 100% Joe Basterdi didn't say a CAT 3 was going to hit Galveston. (Like TampaSpin would say) JUST SAYIN. Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Guess what guys.....ECMWF absolutely nailed this storm. Major cudos to that model in the face of the big-hitter GFS and CMC ensembles completely disagreeing with it for all this time, and now we have a clear winner. ECMWF was stellar and solid from the moment it shifted all the way west many many days ago, and despite being the southern-most outlier, it won out, clear-cut.
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Quoting CybrTeddy:
Recon on its way to Alex.


Should be interesting! Eyewall showing, both ADT sites giving out 4.0s.
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Quoting MiamiHurricanes09:
Tune into the NHC site and your local news for information, not me. But I am 99% sure you are not going to get much from Alex, except some rain.


I think this guy is trying to get to you MH, just ignore him.
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Quoting AstroHurricane001:


Wow. I have NEVER seen a hurricane before that took up the entire Gulf of Mexico. The convection almost stops at the coast but its outer bands are too wide to do that. That means all the dry air over Texas is gone, but Alex has not yet absorbed ex-94L. This storm is going to alter the circulation patterns across the entire Western Hemisphere. If this storm stalls, even on land, terrible flooding could result. It's only the first storm of the season, and even a category one of this size could be devastating.

Meanwhile, flooding in Southern China leaves 382 dead. Link


I have... Hurricane Ike destroyed my house.
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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.