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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Can you see the center at the 5'o clock angle on radar? looks to be moving SW and I know this would be way up in the top part of the clouds being so far off

Member Since: July 14, 2008 Posts: 1 Comments: 9648
Quoting hurrkat05:
kman you have a stall and its going to be a noticeable one...it will not move till that deepening trough over california moves east and picks up alex and sends him north then ne finally out the area...all interests along the texas and sw la coast should keep abreast of future releases on this storm...


The forecast steering maps have the high in place until well after Alex has gone ashore in Mexico. For this to be a stall, and it looks like one, there would have to be a major short term change.

I looked at some WV imagery and steeringlayer stills and to me it looks as if the gulf coast high has retreated some to the East and opened up the weakness just a tad once again.

These are all fine distinctions that require confirmation. Until I see more sat frames I will have to leave it there.
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Quoting WaterWitch11:


i was listening to dr. master show and i swore he said something like that


see i DO know what i'm talking about! just kidding. it's just what i see, but i could be wrong. it kind of looks like it jogged south maybe south west - at least in that particular loop it does
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Thank you dear.I will leave you to your work at hand.
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Link

alex is wanting to dance!!
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1787. Ossqss


Quoting atmoaggie:
Still quite a ragged appearance by cloud top temp.



That is an interesting image ATMO
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Quoting mrsalagranny:
I am sorry Miami if I seemed a lil edgey.Just thought it was srange because the high was there earlier.I know you are entitled to make errors.Afterall we are all human.Please forgive my ignorance as far as weather.Tia
What are you apologizing for? If anybody has to apologize it is me for making the error. Don't worry about it, it's all good.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
WTF Destin Jeff?
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1784. centex
My point, recon is important, critical phase. Maybe next crew if legally possible should get it going.
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1783. scott39
Quoting hurrkat05:
kman you have a stall and its going to be a noticeable one...it will not move till that deepening trough over california moves east and picks up alex and sends him north then ne finally out the area...all interests along the texas and sw la coast should keep abreast of future releases on this storm...
WTH
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1781. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Quoting atmoaggie:
Oh, goody, let's.


Ike


Alex
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Agreed. The banding on the eastern quadrant is out of hand. May pack a significant punch.
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Quoting DestinJeff:


That might have been a mistake :)
Or is that a shower curtain??
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Still quite a ragged appearance by cloud top temp, especially near center.

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Quoting Orcasystems:
Hmm pleasant discovery....
Counting doesn't help....
But the little blue pills and the iggy button appear to do the trick :)


The medium pink ones washed down with a white russian are a family tradition. :))
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1774. Patrap
Member Since: July 3, 2005 Posts: 426 Comments: 129093
Link
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Quoting MiamiHurricanes09:
Very impressive banding on the eastern quadrant, it honestly looks like a beast. Lol.


imagine the megawatt equivalent of that burst
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I am sorry Miami if I seemed a lil edgey.Just thought it was srange because the high was there earlier.I know you are entitled to make errors.Afterall we are all human.Please forgive my ignorance as far as weather.Tia
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Quoting kmanislander:
The high has relaxed ever so little.

Before any conclusions are drawn one way or the other I would suggest we wait for another 2 hours of loops to see if we do indeed have a stall. There has abeen an abrupt course change from NW to W based upon imagery and the storm may have reached the outer edges of the gulf coast high on the Western flank.


Its honestly hard to tell the direction, it slowed but is it stalled? We won't know until more frames come out.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
1768. Patrap
Mmmph,,somebone,pleaseb pass the Saltf ..


This Umm,,Seabfood Platta is umm,goob..

Member Since: July 3, 2005 Posts: 426 Comments: 129093
1767. will45
Quoting kmanislander:
The high has relaxed ever so little.

Before any conclusions are drawn one way or the other I would suggest we wait for another 2 hours of loops to see if we do indeed have a stall. There has abeen an abrupt course change from NW to W based upon imagery and the storm may have reached the outer edges of the gulf coast high on the
Western flank.

May not have to wait 2 hrs. the NHC may say something at 11:00
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Quoting truecajun:
ok. i know im going to get yelled at, but sort of looks like he moved south in the last two frames of RGB loop

http://www.ssd.noaa.gov/goes/east/gmex/flash-rgb.html


i was listening to dr. master show and i swore he said something like that
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Very impressive banding on the eastern quadrant, it honestly looks like a beast. Lol.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting BenBIogger:
My Forecast posted on June 18.


Gotta give you credit for this, you were the closest on last years storm count. I apologize for bashing you last year. I agree with your prediction for this year as well. Good job man!
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Hmm pleasant discovery....
Counting doesn't help....
But the little blue pills and the iggy button appear to do the trick :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting Baltimorebirds:
Can someone compare alex to hurricane ike please.Thank you.
Oh, goody, let's.
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The high has relaxed ever so little.

Before any conclusions are drawn one way or the other I would suggest we wait for another 2 hours of loops to see if we do indeed have a stall. There has been an abrupt course change from NW to W based upon imagery and the storm may have reached the outer edges of the gulf coast high on the Western flank.
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1758. Ossqss


1739 - - An impressive explosion or what ? Wow!
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Quoting atmoaggie:
LOL! You sure got a couple pretty excited... (in some sick, twisted kinda way)
LOL! I know, why do people get so worked up when they see a weakness?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Baltimorebirds:
Alex would sqaush marco.Marco looks like a thunderstorm cell.Anywho what was that storm in the east pacfic at the time.

TS Polo.
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he's practically stalled out, which tells me steering has broke down, and ridge aint doing it's job by pushing him on NW/WNW onshore
Member Since: July 14, 2008 Posts: 1 Comments: 9648
Quoting AstroHurricane001:

I actually have some Typhoon Tip imagery from one of my blogs last year. Check it out here!
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My Forecast posted on June 18.
Quoting BenBIogger:
My Predictions for this Hurricane Season.


17-20 Named Storms
9-12 Hurricanes
5-8 Major Hurricanes

I expect activity to seriously pick up by the Middle of July. A very active Hurricane Season on the horizon.
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I know Miami. The entire band on the east side of the storm is quite impressive.
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ok, so it was the wrong steering map and Alex has not stalled. Is this correct?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting MiamiHurricanes09:
Ok before everyone goes crazy over a simple mistake let me clear things up.

I posted the wrong steering layer.
LOL! You sure got a couple pretty excited... (in some sick, twisted kinda way)
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1746. centex
Read back through post, takes time moves fast. Show someone posted mechanical issue with recon. Also said that is only reason which would make since due to circumstances. Medical issue would also be good reason or faulty data collection. Anyway, I wonder if they are flexible enough to push up the next recon.
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Quoting Xyrus2000:
Well super typhoon tip was around 1380 miles in diameter while Alex is probably around 700 miles in diameter depending on how you measure it.

yes, Tip was the hugest:
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thats a bomb of a rainban on its NE side
Member Since: July 14, 2008 Posts: 1 Comments: 9648
Quoting oddspeed:
Also notice that massive burst of convection over the Yucatan, that's pretty impressive.
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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