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 WaterWitch11:
it is really cool to be able to listen to dr masters while on the blog
yes it is :) even more so while a Cane is in the Gulf...(well, not oficially a Cane)
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Quoting WaterWitch11:


if i remember correctly it was forecasted to be 25-30 feet, by me stating this i am in no way am belittling the damage ike did do.


I think there may have been a couple of isolated pockets of northern Trinity Bay that taken close to that. Maybe I'll be able to find something about it.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting MiamiHurricanes09:
You are bored? How can you find boring a tropical storm on the verge of a hurricane?


not strong enough I suppose
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It'll be a hurricane at this advisory im pretty sure.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
189. IKE
Looks like Alex is heading almost due west for Mexico....

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Quoting MiamiHurricanes09:
You are bored? How can you find boring a tropical storm on the verge of a hurricane?


Don't ask me, ask the other guys.

BTW, how is the Gulf of Guinea doing with cooling?
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:)
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This is a cool one of Katrina

Link
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Quoting hurricanejunky:
Dr Masters, although the satellite presentation and organization of Alex have improved throughout the day today, do you think dry air is still prohibiting it from reaching hurricane status?


It will be a hurricane, just don't expect a major one. Heck why would anyone want a major one?
Member Since: May 27, 2009 Posts: 0 Comments: 4438
Quoting cg2916:


We're looking to see how big this really is, and we're bored.
You are bored? How can you find boring a tropical storm on the verge of a hurricane?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Dr Masters, although the satellite presentation and organization of Alex have improved throughout the day today, do you think dry air is still prohibiting it from reaching hurricane status?
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Quoting MiamiHurricanes09:
Well speak about those implications after Alex passes, but right now pay attention to what it is doing and not comparing it to other systems that Alex can't be compared to. Just my take on it.


Interesting to compare Alex with storms I've actually experienced.
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it is really cool to be able to listen to dr masters while on the blog
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Quoting HoustonTxGal:
Hurrican Fran image



cool picture... :)
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Link

Squall line approaching the Keys that formed on an outflow boundary created by storms over Cuba a few hrs ago...

and now back to the Alex show
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Hurricane Floyd
Link
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Quoting HoustonTxGal:
Hurrican Fran image



Wow.
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Quoting angiest:


What part didn't pan out? Plenty of places along Galveston Bay *west* of the eye got 15 feet of water.

Galveston Island State Park is still a few years from recovery and it is a good 15-20 miles west of landfall.


if i remember correctly it was forecasted to be 25-30 feet, by me stating this i am in no way belittling the damage ike did do.
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Quoting angiest:


What part didn't pan out? Plenty of places along Galveston Bay *west* of the eye got 15+ feet of water.

Galveston Island State Park is still a few years from recovery and it is a good 15-20 miles west of landfall.


many small towns were destoryed.
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Quoting ecflweatherfan:
Miamihurricanes... makes sense to me to the degree that how many people are affected. Also a storm this size, this year, in this region has a lot of implications. That is my take on why.
Well speak about those implications after Alex passes, but right now pay attention to what it is doing and not comparing it to other systems that Alex can't be compared to. Just my take on it.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:

looks impressive
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Hurrican Fran image

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SavannahStorm...

Yea, that's why me and half the Eastern Seaboard sat in traffic for 10-12 hours.

Yep, I was caught in the evacuation. A traffic jam from Cape Canaveral to Orlando (55 miles of bumper to bumper). Let's just hope we don't have to do that one again!!!
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Are some already moving on to the next system? or are they just busy eating crow?
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Allen was a cat 5 three times.
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Quoting MiamiHurricanes09:
Question, why are we comparing the size of Alex to other hurricanes? Just doesn't make much sense to me when we should actually be paying attention to Alex, instead of how big it is compared to Ike.


We're looking to see how big this really is, and we're bored.
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Quoting ecflweatherfan:
Quoting angiest:


136. Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?
Fran 96? I remember it being a large storm but don't know how it compares.


What about Floyd back in 1999. Huge storm, nearly the size of TX.


Ok, yeah, I think Floyd was bigger than Fran.
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Yes, Allen made ladfall just north of Brownsville as a Cat 3.

Hurricane Allen was the first and strongest hurricane of the 1980 Atlantic hurricane season. It was one of the strongest hurricanes in recorded history, one of the few hurricanes to reach Category 5 status on the Saffir-Simpson Hurricane Scale on three separate occasions, and spent more time as a Category 5 than any other Atlantic hurricane. Allen is the second of only two hurricanes in the recorded history of the Atlantic basin to achieve sustained winds of 190 mph (310 km/h), after Hurricane Camille in 1969.
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165. DDR
I'm expecting huge rainfall totals next month,maybe another 20+ inches
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Quoting ecflweatherfan:
Quoting angiest:


136. Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?
Fran 96? I remember it being a large storm but don't know how it compares.


What about Floyd back in 1999. Huge storm, nearly the size of TX.


Yea, that's why me and half the Eastern Seaboard sat in traffic for 10-12 hours.
Member Since: September 22, 2005 Posts: 18 Comments: 2343
Miamihurricanes... makes sense to me to the degree that how many people are affected. Also a storm this size, this year, in this region has a lot of implications. That is my take on why.
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Quoting WaterWitch11:


i remember the storm surge models were off the charts and thankfully they did not pan out.


What part didn't pan out? Plenty of places along Galveston Bay *west* of the eye got 15+ feet of water.

Galveston Island State Park is still a few years from recovery and it is a good 15-20 miles west of landfall.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting angiest:


Brownsville area. Cat 3 I think?

Peaked as Cat 5, possibly on two occasions. Doing this from memory.


wow... it looked very impressive. I didn't really start getting into the Hurricane thing until Rita. We had to evacuate for that one and was gone for about 2 weeks or so. Been interested in them ever since...I did think Humberto was cool. Stayed through that one...
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Question, why are we comparing the size of Alex to other hurricanes? Just doesn't make much sense to me when we should actually be paying attention to Alex, instead of how big it is compared to Ike.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting GlobalWarming:
Dr. Masters, is Alex's track a potential harbinger of the type of tracks that storms might take this season, regarding the steering patterns through the Carribean? Thanks.


I'll let Dr. M. answer for himself, but as for me, I've been expecting a bad western Gulf season for a couple of months. SE Texas has had ridges too early this year not to. Normally we really dont get them until later June through August. I think we started getting ridges here as early as April this year.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting StormChaser81:


Ike was bigger.


i remember the storm surge models were off the charts and thankfully they did not pan out.
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Quoting angiest:


136. Pretty amazing any time of year.

Allen.
Ike.
Alex.

Who else has been this huge?
Fran 96? I remember it being a large storm but don't know how it compares.


What about Floyd back in 1999. Huge storm, nearly the size of TX.
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Quoting CybrTeddy:


The dry air is far less than it was earlier.


You can tell its trying to cut the dry air source off, but hasnt yet.
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Quoting StormChaser81:


Looks can be very deceiving especially with weather. I see dry slots between feeder bands, poor outflow except for the southeast quad.


Way to much dry air is getting ingested.

Yeah I haven't been able to check out water vapor but it certainly seems like some dry air is being swallowed, although I wouldn't really believe that since Alex's convection spans such a large area.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
154. DDR
The gfs is trying to say mr itcz will be behaving bad in and around the Southern windwards,
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Allen info below
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Quoting StormChaser81:


Looks can be very deceiving especially with weather. I see dry slots between feeder bands, poor outflow except for the southeast quad.


Way to much dry air is getting ingested.



The dry air is far less than it was earlier.
Member Since: July 8, 2005 Posts: 259 Comments: 24466
Dr. Masters, is Alex's track a potential harbinger of the type of tracks that storms might take this season, regarding the steering patterns through the Carribean? Thanks.
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Quoting TexasHurricane:


where did this one make landfall at and how strong was it?


Brownsville area. Cat 3 I think?

Peaked as Cat 5, possibly on two occasions. Doing this from memory.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
149. Daveg
So my question is, how much longer, if at all, till Alex slams on the breaks and turns West?

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Quoting HoustonTxGal:
1980 Hurricane Allen image



where did this one make landfall at and how strong was it?
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Quoting twhcracker:


i would like to ask if he thinks Alex will make the oil go into the gulf loop.


Dont think Alex has that much wave action and winds to push it that way, I was told in a briefing that the oil will be pushed more onshore in the FL panhandle area. The winds will come from the southeast.
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Dr. Masters:

I have question about dropsondes. Once they are dropped and reach the surface do they continue to provide tangible data or is that the end of their usefullness?
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Speaking of Frances... she was replaced with Fiona, and this is her first year. Anyone expect she will be an ogre of a storm?
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Pretty much Alex is Ike rotated 90 degrees.
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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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