Alex building an eyewall, still not a hurricane
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
Reader Comments
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Hmm... visibles can be decieving... so still moving WNW/NW.
Check the forecasted moving speed. Serious flooding issues could occur.
Link
Does the rodent have a name?
locked and loaded
here comes another one.
I think the folks at the NHC are sitting there with bated breath because conditions are so good. What they cannot anticipate is what will happen once events begin to unfold. Doesn't look like the much touted wave did anything except get absorbed by the ICTZ.
From the 2 p.m. Discussion:
...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 20N19W 12N21W AND THEN SOUTHWARD ALONG 21W...MOVING WESTWARD 10 TO 15 KT. BROKEN TO OVERCAST MULTILAYERED CLOUDS AND POSSIBLE SHOWERS ARE FROM 11N TO 21N BETWEEN 18W AND 21W. OTHER ITCZ SHOWERS AND THUNDERSTORMS ARE FROM 6N TO 10N BETWEEN 20W AND 24W.
Hold down control button when you click
I will scream as loud as I can if the NHC doesn't classify this as a Cat. 1. Seriously, 981 mb "Tropical Storms" with an eye and eyewall. Is this the new style with Tropical Cyclones?
Jim will likely be crying tomorrow that it went south of him... like it usually does. :P
looks scary
Africa is sure producing some nice waves :\
I think the hurricane winds will be further out than that.
If they collide with a cold front over S. Ontario, I'm in trouble!
And it will dissipate in 2 days. :P
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?
Lets see, weather channel...overpompus announcer hmmm....
This storm ALREADY takes up the entire Gulf, except for a dry slot near Cuba.
I do agree... yes it was having difficulties at the beginning but it sure was able to be to overcome its issues and give great consistency.
Too bad it's headed for Mexico. It will likely cause significant flooding there, but since all the media will be in TX, the public will think that the storm wasn't a big deal..
That appears to be a wobble, which would end up slowing down its forward speed.
Only exception. ;)
Before:
After:
thanks....tried that and it does try to bring up the page but still won't connect....i guess it is something to do with my computer.
Okay thanks. I looked at a link that victoriahurricane posted, and it looks like it's still going WNW/NW.
If it's filling up the empty areas, that means the outer bands are expanding to become wider.
That didn't work, can someone tell me how to post images?
I guess I'm really speculating about where it was headed, but I agree in spirit with your comment. We've all become Media Babes of sorts. (Present company included, and proudly, seeing as we're commenting on Jeff's blog! LMAO!)
Mostly large farming and cattle areas in that part of Mexico...largest city is San Fernando, of maybe 10K people on a busy day. Houses are made of concrete block, but the land is flat so there will be flooding in some areas for sure.
Hmmmm, I guess that could mean more rain for us..
You must upload it on a host site first.
Did you mean infinitesimal? LOL Sorry, that same sort of thing has happened to me more than once. I am laughing with you, not at you.
I thank God my momma was on constant grammar-patrol. My biggest language pet-peeves are the their/there/they're, your/you're, to/too/two issues. lol
I tried so hard to find a way to end one of my sentences in a preposition; I failed miserably.
Do you have your computer set to allow for popups?
Yeah.. but that's sorta understandable because it's an estimate based on just satellite, and it does look more like a high 980 system than a low 980/high 970 system based on satellite. But I can't find a reason why the weakening flag would be on?
Alex has made some massive improvement in the past 3 hours:
Before:
After:
Viewing: 851 - 901
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