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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If Alex slows down he could easily become a category 3 hurricane, let's hope he doesn't.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
St. Simon I know what you are saying, so it is very interesting in what you are saying. I think this is the factor you are alluding too.What has caused this lack of strengthening dry air to the west people don't even read the Doc's post. I mentioned some of this, for the last couple of days but if it's not in the models, I have noticed no one wants to discuss it. Since I have no rep. and surely never will, no need to worry about it's destruction.
Member Since: August 18, 2008 Posts: 0 Comments: 3113
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1539. bappit
Quoting aspectre:
aspectre "Have the Quote, Ignore, ModifyComment, and Filter buttons been disabled?
Or was there an JAVA/etc update that I haven't heard of?
"

1461 ShenValleyFlyFish "browser?"

Firefox

Check your plugins. Also, do you have JavaScript disabled?
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1537. JLPR2
Big bad Alex

Jeez, Alex is huge
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Thanks, Patrap!
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slowing down too
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I watch it in Google Earth via http://tropicalatlantic.com/recon

Quoting Baltimorebirds:
Okay where do you find all the updates on the hurricane hunters flight right now??
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1533. JLPR2
Quoting ShenValleyFlyFish:

Mexicans say you speak Spanish funny and Britons say I speak English real funny.

LOL


I actually like the British accent XD
And the Spain accent with Spanish, yeah, mine is not my favorite. :O
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1531. angiest
Quoting Patrap:
The SSS is outmoded and was designed for Wind Loading on structures decades ago.



We need a better system in time..

How many cat 3's have a 30 ft Storm Surge is my offering from 2005.



Hence my comment about the (E)F tornado scale. The numbers are the same (an historic F-5 like the Moor OK Tornado of 1999 would be rated EF-5 today) but they reworked the damage for modern American structures and *adjusted the wind speeds* to reflect current knowledge. The lowest winds of an EF-5 tornado is lower than the winds of an F-5 tornado, but they produce equivalent damage. It seems the SSS can be reworked in a similar fashion so as not to undo decades of educating the public on what the numbers mean in a relative way.
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Quoting Baltimorebirds:
Okay where do you find all the updates on the hurricane hunters flight right now??
NHC Aircraft Reconnaissance
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting FortBendTX:
good evening all...just wondering. If Alex is moving South of West now and that trend continues, will the ridge to its north have less of an impact on its steering?


Thats what I'm worrying about, but no one in hear has it crossed their minds, buring down in the BOC just wasting time and the high would move on east
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Quoting CybrTeddy:


Its feeding information for the models to run off of on the next run, they only issue advisories at 2, 11, and 8 a.m or p.m unless there is a special change.

I wasn't aware - I thought they would break in once they determined it was a Hurricane
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Quoting centex:
If I read that right the last center fix was S and E of 7PM position.


Yep, I think Alex is going to make a final try to keep going and not make immediate landfall, maybe a loop to the south and east is possible, but Alex needs to get a little stronger really fast to pull this off.
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outerbands hitting tx/la should start sparking up.
is that what you call them "outerbands? lol
Member Since: August 11, 2008 Posts: 3 Comments: 1608
Storm W just pulled out a "wishcaster" and "doomcaster" on Barometer Bob Show. LOL. Meaning he is being neither. He did a great job. Just interrupted by the Norton commercial though.
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When do the HH's fly next?
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1520. centex
If I read that right the last center fix was S and E of 7PM position.
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Quoting StSimonsIslandGAGuy:


When tropical storm Hanna made landfall as a 981 mb tropical storm, I thought there could be large surges in North Carolina to the east of Hanna's landfall point, since she had a large windfield. However, the storm was moving so quickly that gales did not last terribly long, and the surges were not unusual for a tropical storm.

I believe that Hannah was also traveling at the wrong angle for a large surge to build up. To my understanding, a storm traveling 90* to the coast causes the greatest surge and lesser angles will cause the surge to be less concentrated. Don't know this for sure, but that's the notion I have.
Member Since: August 2, 2006 Posts: 46 Comments: 11667
good evening all...just wondering. If Alex is moving South of West now and that trend continues, will the ridge to its north have less of an impact on its steering?
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he's offcourse, he's marooned, Alex playing more games, and still setting records
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Quoting aspectre:
Have the Quote, Ignore, ModifyComment, and Filter buttons been disabled?


Quote working, Ignore not working for me
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Thank you so much.Im sorry if I bothered anyone.
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Quoting Ameister12:

Well it is a hurricane. Recon found 65 knots.


Aww not again... surface.. not flight level ;(
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Quoting angiest:


You might be surprised to hear that the local press aren't reporting the state of recovery anywhere really, except maybe Bolivar.


people around here still have their house ruin.
1511. Patrap
Quoting angiest:


You might be surprised to hear that the local press aren't reporting the state of recovery anywhere really, except maybe Bolivar.


Living in NOLA ,,not much I havent seen in recovery ,or the Onion Layers related to it..but I sure know where your coming from .

And I understand.
Member Since: July 3, 2005 Posts: 424 Comments: 128261
1510. bappit
Quoting MiamiHurricanes09:
Pretty pointless at this point but quite impressive nonetheless.


Not pointless. The assumptions made by the model (computer program) that plotted the image are true in this case. It is the Multi-Platform Tropical Cyclone Surface Wind Analysis as described here. A quick quote about it:

Currently, this product combines information from five data sources to create a mid-level (near 700 hPa) wind analysis using a variational approach described in Knaff and DeMaria (2006). The resulting mid-level winds are then adjusted to the surface applying a very simple single column approach. Over the ocean an adjustment factor is applied, which is a function of radius from the center ranging from 0.9 to 0.7, and the winds are turned 20 degrees toward low pressure. Over land, the oceanic winds are reduced by an additional 20% and turned an additional 20 degrees toward low pressure.

Edit: maybe I should just say that the assumptions are reasonable, that the mid-level circulation provided by their data sources is coupled with a surface circulation like in the tropical cyclones used in verifying the method of analysing the data.
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HH heading right into the NE quadrant, this should be interesting...
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting KEEPEROFTHEGATE:




Where are the "Alex is going to do a loop de loop and start heading south and east and then... east and northeast" doomcasters?
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Quoting DanielPC:
My take on it (and pardon me if I'm repeating what somewhat else said) is that the satellite estimates say hurricane, but the HH haven't been able to find that windspeed.
Those aren't satellite estimates but actually the information sent into the models by the NHC, if you're talking about the FTP, correct me if I'm wrong.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
1506. Patrap
The SSS is outmoded and was designed for Wind Loading on structures decades ago.



We need a better system in time..

How many cat 3's have a 30 ft Storm Surge is my offering from 2005.

Member Since: July 3, 2005 Posts: 424 Comments: 128261
aspectre "Have the Quote, Ignore, ModifyComment, and Filter buttons been disabled?
Or was there an JAVA/etc update that I haven't heard of?
"

1461 ShenValleyFlyFish "browser?"

Firefox
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Quoting mrsalagranny:
I hope nothing does either.I live in Mobile as well.This is the first I have heard of it.Do you have a link I could look at?


yes, the Docs blog... look up :)

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.
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Quoting CyclonicVoyage:
Could this be Alex's calling card ( Alex building an eyewall, still not a hurricane)? And the way off GFDL & HWRF yesterday has been right all along about not intensifying past a TS. Dry air is still evident.

Just sayin :-/


Well it is a hurricane. Recon found 65 knots.
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1502. angiest
Quoting Patrap:


Rural..and Still in the throes of recovery


You might be surprised to hear that the local press aren't reporting the state of recovery anywhere really, except maybe Bolivar.
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Quoting JLPR2:


I find that you guys speak Spanish funny. XD
As you would think we speak English funny. LOL!

Mexicans say you speak Spanish funny and Britons say I speak English real funny.

LOL
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aspectre "Have the Quote, Ignore, ModifyComment, and Filter buttons been disabled?
Or was there an JAVA/etc update that I haven't heard of?
"

1461 ShenValleyFlyFish "browser?"
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Quoting hurricanehanna:

Then why doesn't the NHC change the post?


Its feeding information for the models to run off of on the next run, they only issue advisories at 2, 11, and 8 a.m or p.m unless there is a special change.
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Quoting keithneese:



I've seen that some of the models are forecasting possible development off the Alabama coast this weekend. Since I live on the Alabama coast (Mobile), that kinda has me a little concerned. Hopefully nothing will form.
I hope nothing does either.I live in Mobile as well.This is the first I have heard of it.Do you have a link I could look at?
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Quoting CyclonicVoyage:
Could this be Alex's calling card ( Alex building an eyewall, still not a hurricane)? And the way off GFDL & HWRF yesterday has been right all along about not intensifying past a TS. Dry air is still evident.

Just sayin :-/




what dry air lol

http://www.ssd.noaa.gov/goes/flt/t1/wv-l.jpg
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Quoting Stormchaser2007:
For all the people who are looking at the NHC site and not seeing anything...

They will not issue a special advisory until recon does a NE quad pass.

Simple.
True. I think considering the proximity to land, a special advisory is a certainty, so long as that HH data is in before 9:30 CDT. I'm not following the flight, but it seems like there's plenty of time to do that pass.
Member Since: August 3, 2005 Posts: 10 Comments: 5581
Quoting IKE:


There is some. Not great, but a chance.
I'm looking more towards the Nicaraguan coast. Read up on Jeff Masters' blog where is says "Elsewhere in the tropics", it explains it pretty well.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
i think it will be a hurricane at 11pm

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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.