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:
Alex looks like a pecan swirl....




LOL! Yes he does. Yummy!
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Quoting MiamiHurricanes09:
Wow. I'm impressed. Great call Reed!


Thanks, my current forecast has it hitting the borderline of TX,MX. This however could change, but a NW motion continues, until I see a more WNW motion, and not jogs, I will keep my forecast the same.
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Ike, do you recall Ike from 08?
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Quoting 1900hurricane:
Out of curiosity, where did the term "eat crow" even come from? I've been here since 2006, but I have no idea how the term got started. It's just such a strange idiom to me.

http://en.wikipedia.org/wiki/Eating_crow

And, yeah, it is strange.
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Quoting MiamiHurricanes09:
There is no dry air or eye near or atop the circulation. The dry air slots are located around the outer bands.



you can see it on the vis and RGB, that little slot makes its way from the center all the way to the outside of the storm
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Ike, I think the top graphic is more harmful for us...LOL Alex blows right on by.. the sticky buns stick to the rear end FOREVER!!
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Quoting StSimonsIslandGAGuy:
I guess if Cat 3 is a major then

Cat 4 is a colonel

Cat 5 would be a general.

Haha, epic win right there! And what would category 1 and 2 be?
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That shakey blogger is a hoot.
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335. IKE
Quoting kuppenskup:
How many times has the name "IKE" been mentioned here?


You call?
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Quoting 1900hurricane:
Out of curiosity, where did the term "eat crow" even come from? I've been here since 2006, but I have no idea how the term got started. It's just such a strange idiom to me.
It is an old saying.From way back...
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Quoting IKE:
Alex looks like a pecan swirl....






or a cinnamon roll.

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dry air infiltrating the center
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Quoting IKE:
Alex looks like a pecan swirl....






He does.
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Eating crow (archaically, eating boiled crow) is an English-language idiom meaning humiliation by admitting wrongness or having been proved wrong after taking a strong position.[1] Eating crow is presumably foul-tasting in the same way that being proved wrong might be emotionally hard to swallow.[
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This is only June... we got about 5 months left....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
How many times has the name "IKE" been mentioned here?
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327. IKE
Alex looks like a pecan swirl....




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Out of curiosity, where did the term "eat crow" even come from? I've been here since 2006, but I have no idea how the term got started. It's just such a strange idiom to me.
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Quoting reedzone:
I want to put up my first forecast for Alex because it is a good comparison to the current NHC track.

Photobucket
Wow. I'm impressed. Great call Reed!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
blob watching is better than blob casting... anyday!
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Quoting IKE:


You work for the NHC?


No, I do not! What about the storm that the Nogaps was forming, thoughts?
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Otherwise it's back to blob watching!

Reminds me of a song...hmm,hmm... "I'm a swirl watcher, I'm a swirl watcher, watchin' swirls go by... my,my,my"
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Quoting VAbeachhurricanes:


orrrrr, dry air?
There is no dry air or eye near or atop the circulation. The dry air slots are located around the outer bands.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
This is what happens when people watch frame by frame and do not take the overall movement of a storm over a longer period of time

anyway I will be back later when recon is out
Member Since: March 10, 2010 Posts: 1 Comments: 7872
I want to put up my first forecast for Alex because it is a good comparison to the current NHC track.

Photobucket
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naaaaa, that's what makes this so much fun.. different opinions and ideas. Alex could have gone anywhere that early on.
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317. Daveg

I'll agree that in the last two frames, he has moved more West than North, but there is still a northerly component to his movement. Will need many, many more frames before I'd just yell out "He's moving west!".

In either case, getting lots of rain up here in Austin now.
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Quoting VAbeachhurricanes:


orrrrr, dry air?

this.
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Quoting IKE:


12 hour average is what I've been told. It's been moving WNW for the last 3 advisories(10am, 1pm and this latest one).


It has gone 1.5N and 2.1W in the last 12 hours; basically a NW motion

in the last 24 hours it has gone 2.7N and 2.2W

Hence the NW motion overall still
Member Since: March 10, 2010 Posts: 1 Comments: 7872
I'll eat crow. I predicted an alabama/mississippi landfall a few days ago. Guess I need to go back to school.
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Quoting winter123:
Here goes...

I think i see a eye!



He does look like he is trying to peek out of those clouds
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Quoting yonzabam:
Isn't it the case that the path of hurricanes can be influenced by mountainous terrain?

The huge outer bands of Alex will soon be interacting with Mexico's high Sierra Madre mountain range.

If, as expected, Alex approaches Mexico travelling NW, might the interaction with the mountains not push it in a more northerly direction?
Interaction of land with the outer bands plays an insignificant role in motion.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting midgulfmom:
Not trying to make waves but even Dr. Masters had that in the title of one of his blogs concerning Alex.


Ahhh, the shaman has arrived!
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Quoting winter123:
Here goes...

I think i see a eye!



orrrrr, dry air?
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Quoting hurricanejunky:


Definitely! More like 80 miles south of the TX/MX border instead of 30 like it was before.

not 80 still like 50 mi
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Here goes...

I think i see a eye!

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NHC 4pm update even further south!

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And at times, IKE, even due west (short wobbles). Idk...........
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304. IKE
Quoting TexasHurricane:


Think that will be anytime soon? or do we have a bit of waiting?


May be a minor system in the NE GOM in a few days, although it may not even happen. Maybe a system approaching the islands in a week.

Otherwise it's back to blob watching!
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Quoting ecflweatherfan:
From the NHC 5pm Forecast Discussion:

HOWEVER...THE CYCLONE
HAS TURNED LEFT MORE THAN PREVIOUSLY FORECAST...AND THIS REQUIRES
THE NEW FORECAST TRACK TO BE SHIFTED SOUTHWARD FROM THE PREVIOUS
ADVISORY.


If this is the case, then why do they still call it NW???
I'm sure the question already got answered but motion is averaged over a period of 12 hours. This "new" WNW motion hasn't lasted 12 hours so it is still moving "NNW". BUT if the WNW motion persists for another couple hours it will likely start moving "WNW".
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Isn't it the case that the path of hurricanes can be influenced by mountainous terrain?

The huge outer bands of Alex will soon be interacting with Mexico's high Sierra Madre mountain range.

If, as expected, Alex approaches Mexico travelling NW, might the interaction with the mountains not push it in a more northerly direction?
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301. IKE
Quoting GlobalWarming:


That was always known, Ike, at least by me, it was.


You work for the NHC?
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Alex looks similar in a sense to Hurricane Opal 1995:

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Wavewatch image
Link
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298. IKE
Quoting ecflweatherfan:
From the NHC 5pm Forecast Discussion:

HOWEVER...THE CYCLONE
HAS TURNED LEFT MORE THAN PREVIOUSLY FORECAST...AND THIS REQUIRES
THE NEW FORECAST TRACK TO BE SHIFTED SOUTHWARD FROM THE PREVIOUS
ADVISORY.


If this is the case, then why do they still call it NW???


12 hour average is what I've been told. It's been moving WNW for the last 3 advisories(10am, 1pm and this latest one).
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Quoting IKE:
Shifted slightly south?

That is a very welcome shift South that takes the worst of it into a less populated area. If it keeps the speed up that will ease flooding problems too.
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Look east, young man, look east!
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Quoting IKE:


Thankfully it will be over soon. Then it's on to Bonnie.


Think that will be anytime soon? or do we have a bit of waiting?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting HoustonTxGal:
My in-laws live on the beach in Galveston (west end).. does anyone know what kind of surge they may be looking at there?

I don't believe they are forecasting tides to be more than 1-2' above normal. And now that Alex seems to be turning even more to the left than anticipated, those tide levels may be reduced even more.
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Quoting GlobalWarming:
Texas dodged a bullet, and the NHC, once again, has been proven' impeccably accurate, like always, right, Ike? Remember the wishcasters saying that Alex was either heading up towards TX or LA? What a joke. Anyways, next, right, Ike?
What a joke you are by saying that. Anyways, I should poof you, right?
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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