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 hurrkat05:
levi you may be saying that to early lets see what alex does when it gets near mexico...it's like the 4th quarter in a football game and you are up by 10 with 2 minutes to go and you start to celebrate then the bottom falls out...so lets just wait and see ..


Hardly a celebration for me when I busted the forecast lol.

Alex's forward motion has increased greatly and is now barely north of due west. He is committed to the coast now with this ridge moving to his north. He's not slowing down to allow any latitude gains on the other side of the ridge. It's over now for the track forecast, but south Texas will still get a nasty chunk of this, possibly even some TS-force winds, and Mexico may have to deal with a Cat 2 come tomorrow night. Dangerous situation for them for a storm this early in the season.
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, the upper level low near the Bahamas killed the invest.



am sending that upper level low off too jail and chageing it with muder a invest i and sent that upper level low 30 days
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting IKE:


Hadn't thought about that. I hope it's wrong.


which again would be the definition of SPURIOUS= FALSE or NOT TRUE
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Quoting Levi32:


SHIPS 85mph at 24 hours out looks alright, but if Alex mixes out the dry air you could see him rapidly deepen before landfall...I'll be holding onto my Cat 2 prediction for intensity at landfall.


That's what Miamihurricanes09 and I were thinking, category 2 right before landfall. Same thing happened with Dolly in 2008.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
687. IKE
114 hours...Bubbling Bonnie?

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting primadonnagirl:
IS Alex going NE?

your a troll.
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the sea temper on weather ground page are crap and dont tell the oh thing
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683. IKE
Quoting atmoaggie:
Oh no...that position would be vary bad for oil spill movement.


Hadn't thought about that. I hope it's wrong.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
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


Flood did have to bring that up. Make sure you have a plan if you live in the SE US, Caribbean, or GOM this year. I know you should every year, but the A/B High is a further north and east this year (on average) and will steer storms left more than out to see or up the East Coast of US.

E
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Quoting Levi32:


Don't ummmmmm me. I said "most".
Just Saying
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Quoting IKE:


It's hanging around this run....at 96 hours....



Ike it would seem some of our concerned younger bloggers are unfamiliar with the fact that the definition of SPURIOUS means FALSE or NOT TRUE
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Quoting HurricaneSwirl:


Well he's got two advisories to do so.. that is if they don't upgrade him with a special statement, which I don't think they will.
More likely to come in at 11PM after all the Recon data has been reviewed and analyzed.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting GlobalWarming:
evening, 456.


evening
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IS Alex going NE?
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Quoting IKE:


LOL...may not happen. GFS may be spinning a soggy spurious one.


Do you remember which forecaster coined that phrase?
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Quoting NttyGrtty:
Levi, any comments on ships strength predictions so far? Also, when do you think we'll have a hurricane, despite ships or in agreement with it?


SHIPS 85mph at 24 hours out looks alright, but if Alex mixes out the dry air you could see him rapidly deepen before landfall...I'll be holding onto my Cat 2 prediction for intensity at landfall.
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Quoting IKE:


It's hanging around this run....at 96 hours....

Oh no...that position would be vary bad for oil spill movement.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Is Alex moving WSW now or is it a wobble? My guess since several days ago was landfall between 100-150 miles south of Brownsville. I think that now could be between 70-130 miles.
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Dr. Jeff: What happens to the moisture of Alex 3 or 4 days from now? Any chance it will head NE toward the Dallas area?
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Quoting AstroHurricane001:


Except that ex-94L is now northeast of the Bahamas.


Actually there is no X94L, the upper level low near the Bahamas killed the invest.
Member Since: July 1, 2008 Posts: 13 Comments: 7396
668. IKE
Quoting Floodman:


Man, I love a good spurious low


LOL...may not happen. GFS may be spinning a soggy spurious one.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting StSimonsIslandGAGuy:
jaevortex, models no longer creating that low. Except the GFS, and even that is much weaker than it forecast before.



Oh ok thanks a lot. I was wondering if that low was the same one that IKE had posted about thanks for the link!
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Quoting HoustonTxGal:


TS Allison is the one that came across the US from the Atlantic right? see, I always get those 2 confused...
How could a Houstonian not know Allison all that well?

Was in Beaumont for that one...

Allison (2001) formed from a wave that came from Africa, went to South America, to the Pacific, turned north across central America and developed in the Gulf just offshore from Galveston.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Quoting MiamiHurricanes09:
I will be very surprised if Alex does not become a hurricane today.



Well he's got two advisories to do so.. that is if they don't upgrade him with a special statement, which I don't think they will.
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Quoting Levi32:
This storm speaks powerfully to the fact that the ridge over the SE US doesn't want to move this summer. The fact that this weakness didn't draw him north shows that heights want to build not fall over the United States, and it's the ridge that wants to be dominant, not the trough. This pattern shows us how many storms will want to keep WNW tracks this year, with less recurving going on near the US. This is why the SE US coast is under the gun from long-track storms that may make it all the way across still moving WNW. Nasty pattern shaping up here.

Look at the big positive height anomalies over the SE Canadian Maritimes and northeast United States. That setup is deadly for US landfalls....that pattern is favorable for activity in the tropics with storms that pass underneath the ridge without recurving and keeping a WNW track right into the United States and Caribbean.

ECMWF/GFS comparison 8-10 day 500mb heights and anomalies"

Not good at all. Hope Miami gets NO storms this year. Although it looks like we will after reading that.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
There is also a disturbance over Central Texas combined with the moisture from Alex and some daytime heating equals a wet day.
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Matamoros blogger here... been raining off and on since morning. ..people here have been extremely lax and no real preparation that I can see. Some do not even know about the storm. Amazing!
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Quoting AstroHurricane001:


Except that ex-94L is now northeast of the Bahamas.


ex-94L is no where. its gone. that's the ULL that tore it apart.
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656. IKE
Quoting AstroHurricane001:


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


It's hanging around this run....at 96 hours....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
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


Don't ummmmmm me. I said "most".
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Quoting IKE:


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.


Ahh ok thought so, thanks IKE! :)
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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.
Levi, any comments on ships strength predictions so far? Also, when do you think we'll have a hurricane, despite ships or in agreement with it?
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01L/H/A/C1
MARK
23.2N/94.4W


POINT OF IMPACT NEAR 23.6N 97.8W
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Quoting reedzone:
My first forecast for Alex, maybe it was right all along..

Photobucket


Except that ex-94L is now northeast of the Bahamas.
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Quoting UpperLevelLOL:


Holy cow you are terrible at detecting trolls


Doesn't seem like a troll to me. Anyway it doesn't matter if he is or not, I was trying to be helpful to him by providing those graphics (unfortunately I modified them to say NEAR 0% instead of flat out 0, and then the graphics stopped working so I just took the post out..) I don't know why you would slam me for trying to help LOL
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Reedzone - You definitely called it.

Hopefully you are as good all season long.
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Outer rainbands



Visible loop

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Thanks!
Quoting 1900hurricane:

ECMWF
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This storm speaks powerfully to the fact that the ridge over the SE US doesn't want to move this summer. The fact that this weakness didn't draw him north shows that heights want to build not fall over the United States, and it's the ridge that wants to be dominant, not the trough. This pattern shows us how many storms will want to keep WNW tracks this year, with less recurving going on near the US. This is why the SE US coast is under the gun from long-track storms that may make it all the way across still moving WNW. Nasty pattern shaping up here.

Look at the big positive height anomalies over the SE Canadian Maritimes and northeast United States. That setup is deadly for US landfalls....that pattern is favorable for activity in the tropics with storms that pass underneath the ridge without recurving and keeping a WNW track right into the United States and Caribbean.

ECMWF/GFS comparison 8-10 day 500mb heights and anomalies"

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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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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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