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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Pretty much Alex is Ike rotated 90 degrees.
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Quoting kuppenskup:
Allen in 1980-Anyone remember that one?


I remember seeing a pic of that when it was in the GOM, just like Alex, but more clouds. a Buzz saw look, covered the entire western GOM.
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Quoting angiest:


I was speaking of Atlantic storms. ;P


In that case Ike, im pretty sure.
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Quoting shauntanner:
Questions for Dr. Masters on the Hurricane Haven can be asked here.

You can listen to the Hurricane Haven here

http://www.wunderground.com/wxradio/wubroadcast.html


i would like to ask if he thinks Alex will make the oil go into the gulf loop.
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1980 Hurricane Allen image

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Quoting MiamiHurricanes09:
Latest visible image makes me truly believe that Alex is a hurricane. Recon to go in and investigate at 8PM EDT.



Looks can be very deceiving especially with weather. I see dry slots between feeder bands, poor outflow except for the southeast quad.


Way to much dry air is getting ingested.

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Quoting angiest:


Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?

Fran 96? I remember it being a large storm but don't know how it compares.
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Quoting StormChaser81:


Super Typhoon Tip was the biggest storm in history, good luck getting that big in the Atlantic or GOM.


Somehow I don't think that would be "luck". If I saw that coming... wow... I'm not sure WHAT I would do if I saw that coming. Because running sure wouldn't do much... :-(
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Quoting StSimonsIslandGAGuy:


stormchaser81 is correct.


Ike:



Alex:

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Quoting Hurricanes101:


Ivan, Frances too


Frances was so big in the wind field that I lost power for 2 weeks over 48 hours of TS force sustained winds. The center passed well south of me.
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132. Daveg
Interesting yet again.... as the blog says... the models changed yet again. The reliable ones now focusing BACK on a TX/MX border landing.

Keeps the head spinning trying to keep up!

Link
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Allen in 1980-Anyone remember that one?
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Quoting StormChaser81:


Super Typhoon Tip was the biggest storm in history, good luck getting that big in the Atlantic or GOM.


I was speaking of Atlantic storms. ;P
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting reedzone:


Can't forget Floyd in the Bahamas. Looked like a giant buzz saw lol.


Allen in 1980, any
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Quoting MiamiHurricanes09:
Latest visible image makes me truly believe that Alex is a hurricane. Recon to go in and investigate at 8PM EDT.



What a beauty!
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Quoting reedzone:


Can't forget Floyd in the Bahamas. Looked like a giant buzz saw lol.


Ivan, Frances too
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Quoting angiest:


Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?


Can't forget Floyd in the Bahamas. Looked like a giant buzz saw lol.
Member Since: Posts: Comments:
Quoting angiest:


Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?


Super Typhoon Tip was the biggest storm in history, good luck getting that big in the Atlantic or GOM.
Member Since: Posts: Comments:
Latest visible image makes me truly believe that Alex is a hurricane. Recon to go in and investigate at 8PM EDT.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting ssmate:
Thanks Flood.


No worries, mate...anytime!
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Member Since: July 15, 2006 Posts: 174 Comments: 54358
Quoting shauntanner:
Questions for Dr. Masters on the Hurricane Haven can be asked here.

You can listen to the Hurricane Haven here

http://www.wunderground.com/wxradio/wubroadcast.html


Ok, Dr. Masters, what do you think of the wave train this year?
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The lastest visible is looking better....

I will be back tomorrow and we will see where alex is.....if not on shore already....
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Quoting RecordSeason:
108:

Who in their right mind would be on a ship in THAT!!


Lots of ships go through storms like that, Has nothing to do with being in the right mind, ships are not that fast and most of the time they cant out run the storm.
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Quoting BiloxiIsle:

Seriously, let go of this!


I find it a shame that we have serious mets that try to come on here and share their knowledge about weather and then our outspoken 'kiddycasters' can't help but run them off with their unnecessary sandbox antics. Most of which are not even forecast related.

Edit: Not directed at BiloxiIsle, I'm agreeing with your comment!!!
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Quoting natrwalkn:
@59 Reedzone: I enjoy reading your forecasts and even Dr. M previously posted about the possibility of Alex going farther north.


Thanks, read post 107
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114. shauntanner (Admin)
Questions for Dr. Masters on the Hurricane Haven can be asked here.

You can listen to the Hurricane Haven here

http://www.wunderground.com/wxradio/wubroadcast.html
Quoting reedzone:
Looking at the steering flow, it's easy to see why Alex keeps wobbling west, a WNW should start occurring if not have already. I'm still pinning my landfall prediction on the border of TX/MX until I see this trend continue for the next few hours. Also, notice the size of Alex, covers the whole GOM with feder bands, pretty amazing for June.


Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Thanks Flood.
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Quoting skepticall2:


Have had to sit in that line hours before oh so boring.


When we were in Rockport last year we got stuck in that line not realizing that they still had a ferry and not a bridge. Took a long time to get to where we could pull a three point turn and get back to Aransas Pass.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting soloco:
Someone tell OZ to be careful crossing into Mexico....I do it 5 days a week, and those teenagers with AKs are typically uncooperative of anything they think is....um....well.....weird. (no offense)
IMO, he should just stay in Brownsville and if and when he knows for sure that the eyewall is going to pass south of it to move.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Looking at the steering flow, it's easy to see why Alex keeps wobbling west, a WNW should start occurring if not have already. I'm still pinning my landfall prediction on the border of TX/MX until I see this trend continue for the next few hours. Also, notice the size of Alex, covers the whole GOM with feder bands, pretty amazing for June.
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The bridging high is slamming the door quickly on Alex moving much further N. Good thing this happened when it did or Alex could have been a major in time.

Member Since: August 19, 2006 Posts: 0 Comments: 15842
Someone tell OZ to be careful crossing into Mexico....I do it 5 days a week, and those teenagers with AKs are typically uncooperative of anything they think is....um....well.....weird. (no offense)
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UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 29 JUN 2010 Time : 184500 UTC
Lat : 23:05:02 N Lon : 93:29:41 W


CI# /Pressure/ Vmax
3.8 / 990.2mb/ 61.0kt


Final T# Adj T# Raw T#
3.7 4.0 4.2

Latitude bias adjustment to MSLP : +0.4mb

Center Temp : -67.9C Cloud Region Temp : -66.6C

Scene Type : UNIFORM CDO CLOUD REGION
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@59 Reedzone: I enjoy reading your forecasts and even Dr. M previously posted about the possibility of Alex going farther north.
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Quoting RecordSeason:
If you still think Ike was bigger, click here.


Ike was bigger.
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101. shauntanner (Admin)
Listen to Dr. Masters NOW, at http://www.wunderground.com/wxradio/wubroadcast.html

List any questions you have here.

Shaun
Quoting Floodman:


Wait...you ignored Reed but you didn't Stormkat?


Should I ignore stormkat, I havnt seen that name very much, I must be missing the fun.
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Wow, RGB loop
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To see a storm like this in june,is somewhat disturbing.
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Prediction for 5 pm.
70 mph (nearing hurricane status)
981 mb.
Moving WNW.
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Latrendsetter... what does that have to do with the this blog?
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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.