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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1443. bappit
1328

Tell Barometer Bob if you see him:

Laguna Madre is pronounced

Lah-goo-nah

not

Lah-gua-na

That's the mother of all lizards? Don't know Spanish.
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Quoting MrstormX:
Recon heading back to COC.


Nope, northerly leg of the triangle now.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Have the Quote, Ignore, ModifyComment, and Filter buttons been disabled?
Or was there an JAVA/etc update that I haven't heard of?
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weatherman12345 and to also not cuase panic.
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Quoting nrtiwlnvragn:


They have done it before, indicating a change in status at the model cycle time and then later change it. They also include the following disclaimer:

Users are also cautioned that the data in these files are subject to frequent revisions and can differ from information issued in official NHC products.


That being said, I don't think they will change it.

Heh, and all of the other products that get info from the ftp server read "Hurricane Alex" whether that was the intention or not: http://rammb.cira.colostate.edu/products/tc_realtime/storm.asp?storm_identifier=AL012010
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NHC HAS NOT UPGRADED ALEX YET!!! NO ADVISORY OF UPGRADE HAS BEEN ISSUED, THEY WILL DO SO WHEN IT IS OFFICIAL!
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Quoting MrstormX:
Recon heading back to COC.
Awesome! It would be pretty freaky if the pressure is less than 973mb.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
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1434. Patrap
Quoting nrtiwlnvragn:


They have done it before, indicating a change in status at the model cycle time and then later change it. They also include the following disclaimer:

Users are also cautioned that the data in these files are subject to frequent revisions and can differ from information issued in official NHC products.


That being said, I don't think they will change it.


3 Plus's and a Clap of Hands
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Quoting ecflweatherfan:
I definitely do not doubt that one one bit MiamiHurricanes09. Probably be a special statement sooner than that if upgraded sooner!
It is likely they will release a special statement, imo.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Recon heading back to COC.
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Quoting Orcasystems:


I don't think it has enough sea room left due to its size? It might make CAT 1 but no higher I think.


i agree
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The next advisory is a t 11 EST right.?
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1428. Or4590
Quoting ecflweatherfan:
It is not official until the NHC says so... they haven't upgraded yet! Sorry, but nice try :-)


Alex is a hurricane now.
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Quoting angiest:


Last advisory on Ike before landfall was 953mb.

Link

That was also bumped down a little on post-storm analysis, down to 950 mb at landfall due to onshore pressure readings.

Hurricane Ike Post Storm Analysis
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Quoting AllStar17:
Watch this wave at is moves across the Atlantic:
Watch it do a sneak attack on us.It's alex is a distraction.Lol.Mark sudduth says he expects development between africa and the lessler antilies this week or next week.
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Last visible image filtered with UV and IR filters..


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IKE looks like SW to ya?
Member Since: July 14, 2008 Posts: 1 Comments: 9645
Quoting Patrap:
God I hope they Upgrade..

The Suspense is Just Killing the Cyclone




lmao
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1422. angiest
Quoting hurricanehanna:
calling for lots of rain here in S. LA for several days....Alex is HUGE I tell ya


In Katy (west Houston), TX we had a pretty good band move through an hour and a half ago.
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I definitely do not doubt that one one bit MiamiHurricanes09. Probably be a special statement sooner than that if upgraded sooner!
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Quoting atmoaggie:
If these 3 guys didn't modify the line from the best track files on the ftp server, it's coming soon to a NHC webpage near you, rest assured.


They have done it before, indicating a change in status at the model cycle time and then later change it. They also include the following disclaimer:

Users are also cautioned that the data in these files are subject to frequent revisions and can differ from information issued in official NHC products.


That being said, I don't think they will change it.
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Quoting StSimonsIslandGAGuy:



Unless I am looking at the wrong ATCF--the one I pulled up has Alex reaching hurricane strength at 2 am tonight.
The one CT just posted is for 00 UTC June 30. An hour ago. Guess we'll see soon enough.
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WSW. lol. Great job Scottsvb.

Clouds are starting to flatten out in the NW quad, high pressure is kickin.
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Yes, Wilma was 882 or lower. There was about a 12 hour period during Wilma's peak intensity in which they had nobody flying in it, and it was probably stronger. During this time it's wind speeds were being reported as 190mph sustained, though it is now said to have been 185mph.
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Quoting Patrap:
God I hope they Upgrade..

The Suspense is Just Killing the Cyclone




I don't think it has enough sea room left due to its size? It might make CAT 1 but no higher I think.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting ecflweatherfan:
It is not official until the NHC says so... they haven't upgraded yet! Sorry, but nice try :-)
Believe me it will be a hurricane before 11PM EDT. It's isn't official but it is certain. :)
Member Since: September 2, 2009 Posts: 130 Comments: 21194
My ears keep popping, I wonder why? hmm
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1412. angiest
Quoting atmoaggie:
Ooooo. Good question.
Guess they just want to use the best available, whatever that may be.


Well, in the East and Central Pacific, hurricanes and typhoons are mostly shipping and aviation problems. In the Atlantic there isn't much oceanic real estate (relatively speaking) and a lot of vulnerable population, so they probably wait for better data. But for an "average" storm satellite seems to give a good idea of pressure and wind speed.
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primaddonnagirl.I wouldn't be exciting for a hurricane.For people that are saying that where do you see it as a hurricane look all over the blog......
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Watch this wave at is moves across the Atlantic:
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Quoting MechEngMet:
1380 Atmo: You are correct. I round to the nearest tenth after my 2nd bourbon.
Well, given that it is really 1.15077xxxx (from memory), your tenth shoulda been a deuce.
(sry, just yankin yer chain, now.)
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1408. Daveg
Quoting stormpetrol:
I noticed Alex samed to move WSW in the last few loops, definitely a Mexico landfall now I'm thinking!


Definitely WNW for a bit now. Still trying to go north a bit, just not getting far. Slowly pushing away from 23N.

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Hurricane Alex.

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NHC still hasnt called it.
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1405. Patrap
God I hope they Upgrade..

The Suspense is Just Killing the Cyclone


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South of track and heading westerly.



AOI

AOI

AOI

Hurricane Hunter Data

TS BUSTED FORECAST ALIBI
Member Since: October 1, 2007 Posts: 81 Comments: 26511
It is not official until the NHC says so... they haven't upgraded yet! Sorry, but nice try :-)
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Quoting ecflweatherfan:
primadonna... is it officially a hurricane? If so, please link your information.
If these 3 guys didn't modify the line from the best track files on the ftp server, it's coming soon to a NHC webpage near you, rest assured.
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Quoting ecflweatherfan:
primadonna... is it officially a hurricane? If so, please link your information.


Yea Alex is a hurricane for those just joining in.


AL, 01, 2010063000, , BEST, 0, 230N, 944W, 65, 974, HU, 64, NEQ, 15, 15, 15, 15, 1006, 250, 15, 0, 0, L, 0, , 0, 0, ALEX, D,
Member Since: July 8, 2005 Posts: 259 Comments: 24455
1380 Atmo: You are correct. I round to the nearest tenth after my 2nd bourbon.
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Quoting ecflweatherfan:
primadonna... is it officially a hurricane? If so, please link your information.
AL, 01, 2010063000, , BEST, 0, 230N, 944W, 65, 973, HU,
Member Since: September 2, 2009 Posts: 130 Comments: 21194
calling for lots of rain here in S. LA for several days....Alex is HUGE I tell ya
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1396. angiest
Quoting MZV:


There is not good correlation between eye size and storm strength. I think Frances had a massive eye, 70 miles or so.


I think it was Fran that had the monster 70-80 mile wide eye at one time, and I am aware of the lack of correlation. :) But superlatives are intersting.
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Quoting primadonnagirl:
alex is finally a cane!
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bb show storm vgood bbob offal
had to turn off
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1393. Patrap
The Cat Number never means squat.
Been beating that dead Squid for 5 years.

Its the Wind Load and Surge that makes the Impact.

Always.



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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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