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 nrtiwlnvragn:


No support from the parallel GFS, which performed well with Alex.
I saw that too.
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Quoting primadonnagirl:
IS Alex going NE?


No
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Quoting hydrus:
It is great..I finally typed pine hole eye. I feel like i am really contributing now...jk....really...jk:)

well... you were the first to spot it.
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Strong curved banding into the center continues....eyewall continues to mature in its formative stages.



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Check out this link with very useful info. on Alex...Link
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earliest recent hurricane was Cindy 2005. Alex looks like he will surpass her. Also a hurricane in June has not occurred for a good while now. Alex, however is not the earliest hurricane. The date for the first hurricane is Aug 10.
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737. IKE
Quoting nrtiwlnvragn:


No support from the parallel GFS, which performed well with Alex.


GFS probably over doing it.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
May someone please post a link of the GOES Rapid Scan Satellite (IR not VIS)... and another thing the Euro is spinning up something in the Caribbean in about 6-8 days from either the wave that just moved off of Africa this morning or the wave with a ton of convection getting ready to emerge. Are any of the other models showing this and are they being consistent on it?
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Quoting IKE:


Hadn't thought about that. I hope it's wrong.
The low cetnered about your longitude would be great, pushing the oil away from the marshes and out to the gulf where it will get weathered enough to just be tar by the time it gets to shore.

The low being centered mid-Louisiana would be ruinous for all of us...
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Quoting gator23:


LMAO! Thank You!
It is great..I finally typed pine hole eye. I feel like i am really contributing now...jk....really...jk:)
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I'm not sure how to interoperate this, but I can at least figure out that someone's going to be dumped on. From the ECMWF Page.

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Quoting hurrkat05:
ok miami i know i said my mistake..
Just clearing it up.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting bohonkweatherman:
There is also a disturbance over Central Texas combined with the moisture from Alex and some daytime heating equals a wet day.


Cold front is colliding with Alex's outer bands.
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726. IKE
PROGNOSTIC DISCUSSION FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS
NWS CLIMATE PREDICTION CENTER CAMP SPRINGS, MD
300 PM EDT TUE JUNE 29 2010

6-10 DAY OUTLOOK FOR JUL 05 - 09 2010


ANTICIPATED CLOUDINESS AND ABOVE-MEDIAN RAINFALL
ACROSS PARTS OF THE GULF COAST FAVOR BELOW-NORMAL TEMPERATURES DURING THE
PERIOD IN THIS AREA. THIS IS ALSO SUPPORTED IN PART BY DOWNSCALED TEMPERATURE
TOOLS AND HISTORICAL ANALAOGS.


THERE IS AN ENHANCED CHANCE FOR ABOVE-MEDIAN RAINFALL ALONG THE GULF COAST
STRETCHING INTO THE GREAT PLAINS AND GREAT LAKES. POTENTIAL LEFTOVER MOISTURE
FROM HURRICANE ALEX AND A CONTINUED FLOW OF TROPICAL MOISTURE FROM THE GULF OF
MEXICO AROUND HIGH PRESSURE ACROSS THE EASTERN U.S. FAVORS ENHANCED RAINFALL IN
THIS REGION.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Really glad to see you're doing better Weather456 :)
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Alex clearly has a visible eye at 23N/94W , i would say 80 mph hurricane next update
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Quoting hurrkat05:
gator if alex moves inland it coud be picked up by the trough and head ne no need to call her a troll...its and opinion man deal with it..
Note: You said after it makes landfall, she said it is moving NE.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
CI# /Pressure/ Vmax
4.0 / 987.3mb/ 65.0kt
ADT estimates

29/1745 UTC 23.0N 93.6W T4.0/4.0 ALEX -- Atlantic
SAB estimates
Member Since: July 8, 2005 Posts: 259 Comments: 24574
Quoting GlobalWarming:
looking forward to your july outlook, 456.


Next sunday, as soon as Alex clears the scene
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Quoting bohonkweatherman:
Come on I said Northern Mexico days ago, talk about getting lucky! :)


Me too! First as a wishcaster but then with the evidence to support it! It even might be passing just over my city!
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29/1745 UTC 23.0N 93.6W T4.0/4.0 ALEX -- Atlantic

No surprise here since the curve banding is pretty tight.

4.0 is 75 mph.
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Quoting KEEPEROFTHEGATE:
01L/H/A/C1
MARK
23.2N/94.4W


POINT OF IMPACT NEAR 23.6N 97.8W


It's wobbling to the WSW!
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Quoting miguel617:
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!


thanks for posting, that's very scary. would love to see pics and vid if you can, but of course safety first please!
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706 - :-)
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Quoting IKE:
114 hours...Bubbling Bonnie?



No support from the parallel GFS, which performed well with Alex.
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Quoting hydrus:
........................Looks like an eye in there. look, it is a pin hole eye....:)


LMAO! Thank You!
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Quoting Weather456:


yea we are....thanks


Glad to hear it.
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Quoting atmoaggie:
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.


Fairly close to where Alicia formed some 18 years earlier. That's a nasty bit of space there, that is. That's why it's always important to watch the things that drift into the GOM during the hot months!! It's not a good idea to let things sit in the boiling pot!!
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Quoting GlobalWarming:
i hope you are yours are doing well, 456.


yea we are....thanks
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........................Looks like an eye in there.
Quoting gator23:

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

"I see a pin...."
look, it is a pin hole eye....:)
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this new firefox 4.0 beta is nic
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting Weather456:
Eye feature clearly visible....likely a hurricane




yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
703. Daveg

Am I high (don't answer that) or has the forward motion really slowed over the past couple of hours?
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Quoting hurrkat05:
gator if alex moves inland it coud be picked up by the trough and head ne no need to call her a troll...its and opinion man deal with it..

right I agree. My opinion is shes a troll so you deal with it
1) she didnt say that she said IS IT MOVING NE
2)she has been posting trollish things all day
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Quoting Baltimorebirds:
Alex still not a hurricane I see.Nothing has changed since this morning.
Nothing? You might want to review the satellite imagery.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Stay Safe Texas
http://www.youtube.com/watch?v=wVjdMLAMbM0&feature=player_embedded
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Eye feature clearly visible....likely a hurricane

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Quoting Baltimorebirds:
Alex still not a hurricane I see.Nothing has changed since this morning.


Alex has been fighting some dry air earlier, but since 5 p.m., it has wrapped up well and a Hurricane is likely at 8 p.m.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting IKE:
114 hours...Bubbling Bonnie?




may be
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
May someone please post a link of the GOES Rapid Scan Satellite (IR not VIS)
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Quoting Goldenblack:


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


LOL, out to sea....geesh, it is like I am a texter or something....

I also meant to mention that the position of the High is similar to 04 05 along with all the other elements (lower sheer, except for early 04, warm seas...)
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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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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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