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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not even there yet and it found this


23:26:00Z 24.883N 95.550W 579.3 mb
(~ 17.11 inHg) 4,635 meters
(~ 15,207 feet) 994.7 mb
(~ 29.37 inHg) - From 51° at 39 knots
(From the NE at ~ 44.8 mph) 4.0°C
(~ 39.2°F) -1.2°C
(~ 29.8°F) 41 knots
(~ 47.1 mph) - - - -
23:26:30Z 24.867N 95.600W 604.1 mb
(~ 17.84 inHg) 4,314 meters
(~ 14,154 feet) 996.6 mb
(~ 29.43 inHg) - From 59° at 42 knots
(From the ENE at ~ 48.3 mph) 5.6°C
(~ 42.1°F) -0.2°C
(~ 31.6°F) 43 knots
(~ 49.4 mph)
Member Since: May 21, 2006 Posts: 5089 Comments: 114024
Quoting IKE:
972....sure to draw responses. I think that's what you're after.


We gonna get him one of these days i promise lol
Member Since: Posts: Comments:
Wow looks like Alex is filling up now, getting rid of all that dry air.
Eyewall is almost complete, if not 100% done. You can see it on the water vapor. It's going to be a small eye (5-10 miles or so wide).

Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting IKE:
972....sure to draw responses. I think that's what you're after.


Doh.. I just got troll'd lol
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting HurricaneSwirl:


A thing of the past?? I bet you wouldn't be saying that if you lived in Tamaulipas!
It's kind of sad that he said that, whatever, that's another one to the list.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Back later
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Quoting nrtiwlnvragn:


The Final T# was less than the previous Final T#, which sets the flag to ON.

Text History


I know that, but why would it be lower than it was previously?
Member Since: July 7, 2008 Posts: 2 Comments: 3237
983. IKE
972....sure to draw responses. I think that's what you're after.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting victoriahurricane:


Firefox


It should work with Firefox. Type the following in the comment box:

<img src="$IMAGE_URL" alt="" />

And that should post it.
Member Since: Posts: Comments:
Quoting GlobalWarming:
Evening, Big K! It's time to move on, sir. Alex is now officially a thing of the past, for most of us on here. Next up, Bonnie, any candidates out there, as of yet? ^_^.


A thing of the past?? I bet you wouldn't be saying that if you lived in Tamaulipas!
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting MiamiHurricanes09:
Looking at animation it looks that way to me too. Let's see if it becomes a trend.


Probably is.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting SavannahStorm:


Loop.


my god in this image it makes it look like a big bully.
Quoting HurricaneSwirl:
What's wrong with this?

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 29 JUN 2010 Time : 221500 UTC
Lat : 23:17:40 N Lon : 94:09:38 W


CI# /Pressure/ Vmax
4.0 / 987.3mb/ 65.0kt


Final T# Adj T# Raw T#
3.9 3.8 3.8

Latitude bias adjustment to MSLP : +0.3mb

Center Temp : -53.0C Cloud Region Temp : -61.8C

Scene Type : EMBEDDED CENTER CLOUD REGION

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : ON
Rapid Dissipation Flag : OFF

It's been on since it got off of land, it was off for a second and now it's back on again. wth?


The Final T# was less than the previous Final T#, which sets the flag to ON.

Text History
Member Since: September 23, 2005 Posts: 13 Comments: 10453
Quoting kmanislander:


Looks like W to me.
Looking at animation it looks that way to me too. Let's see if it becomes a trend.
Member Since: September 2, 2009 Posts: 130 Comments: 21032


Looks like he's finally filling in the dry air pockets
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Member Since: June 9, 2007 Posts: 4 Comments: 15718
Boy are we going to be bored after Alex makes landfall :) Might actually be a WSW bobble, and then a normalized track of due west.
Member Since: May 27, 2009 Posts: 0 Comments: 4355


Loop.
Member Since: Posts: Comments:
How's the HH doing? :) Seems out friend Alex is plumping up nicely.
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969. txjac
I know that I live in Houston and they are preparing at work in case of flooding. And of course, we can all work from home. So we are expecting rain ...it floods on this side of town when we get a good bit of rain that isnt even related in any way to a TS or hurricane
Member Since: April 24, 2010 Posts: 1 Comments: 2350
Quoting MiamiHurricanes09:
Yes he asked how we could verify and I just said when the next advisory comes out.


Ahh gotcha lol. :p
thanks kman
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Quoting Stormchaser2007:
Im willing to bet that Alex's pressure is anywhere from 979mb-975mb now.

Agree.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting RecordSeason:
Not very often you see a single storm simultaneously producing rainfall in 6 or 7 U.S. states and as many as 6 or more foreign countries.



and



and





Oh wow, looking at that first image, were those thunderstorms we got in C GA today from Alex?? Or were they just pop-ups. Too close to tell for me!
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting duajones78413:
what is Alex's true direction right now?


Looks like W to me.
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Recon is descending into Alex now. Looks like they'll approach from the west... that means we won't get a peak wind reading until later they take a pass through the NE quadrant.
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Quoting jaevortex:


the person you just quoted was the one xcool just said told him about Alex becoming a hurricane
Yes he asked how we could verify and I just said when the next advisory comes out.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
HH descending now
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Quoting MiamiHurricanes09:
Still about another hour/hour and a half before they get to the COC.



Gracias
Member Since: May 27, 2009 Posts: 0 Comments: 4355
Quoting AstroHurricane001:


10 inches of rain sure sounds like a lot.


we are suppose to get 10?? I live in the orange area, about 15 min from the LA border....
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Quoting Stormchaser2007:
Im willing to bet that Alex's pressure is anywhere from 979mb-975mb now.



Yup I said earlier it wouldn't surprise me one bit if we saw sub 980 readings.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting plywoodstatenative:
When is South Florida going to get some sort of relief from this heat?


NYC and the rest of the Mid Atlantic was hotter than the southeast. Be glad you're down there! Although... we are getting a refreshing break in the next few days...
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting victoriahurricane:


That didn't work, can someone tell me how to post images?


Too post an image,go too the page with an image and highlight the url and press Ctrl+C.Click Image right above the "Your comment"box.If it blocks the pop-up,a tiny yellow bar will appear at the top of the page,Click on it and click"Tempoarily allow pop-ups from this website".Click on image again if you had to unblock pop-ups.Click in the typing box and delete the HTTP://in the box and press Ctrl+V.Press OK,your done!
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what is Alex's true direction right now?
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Quoting MrstormX:
Hey Miami, when is the next recon? The aircraft page isn't working for me.
Still about another hour/hour and a half before they get to the COC.

Member Since: September 2, 2009 Posts: 130 Comments: 21032
I give up lol
Member Since: October 16, 2008 Posts: 0 Comments: 544
Quoting AstroHurricane001:


Could the convection coming off Africa merge with the wave now in the ICTZ, and spawn yet another supersize storm similar to Alex?


It's a good possibility if conditions approve of it.
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Quoting MiamiHurricanes09:
When the 8PM advisory is released.

Xcool will definitely brownie points if he is right.


the person you just quoted was the one xcool just said told him about Alex becoming a hurricane
plywoodstatenative... You know the relief from the heat will not come until late October/November. LOL!
Member Since: March 19, 2010 Posts: 0 Comments: 1146
Im willing to bet that Alex's pressure is anywhere from 979mb-975mb now.

Member Since: June 9, 2007 Posts: 4 Comments: 15718
Quoting xcool:
Snowlover123 he just told me ..he Professional-Met that all iknow thanks.


???
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting MrstormX:
Hey Miami, when is the next recon? The aircraft page isn't working for me.
they are ESE of Brownsville heading in
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Good afternoon

I just ran a long vis loop and it appears to me that Alex is tracking due W now. I haven't read back over the blog so don't know if any comments have been posted on this yet but NW looks to be over.
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Quoting whipster:


You are correct. I lived in the area for 3 years in Grad school. Nice "Texas-like" area of Mexico. Came back with a wife :)


Good for you. Where were you doing your grad studies? In ag?
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Quoting MiamiHurricanes09:
That is a satellite estimate and not the actual intensity. Current minimum pressure is 981.0mb and is likely to decrease during the next 24 hours.


Yep.
Member Since: July 7, 2008 Posts: 2 Comments: 3237

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.