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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1693. xcool
2010 first hurricane wow crazy
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Interesting.

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Quoting CybrTeddy:


Where did you hear that?



weather.com
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Quoting centex:
Other than speculation, what is up with recon? They report historical pressure for TS and put head between legs on going home?


They had a mechanical failure
Member Since: March 10, 2010 Posts: 1 Comments: 7683
Quoting Torgen:


I thought he was starting to well up cooler water, and hadn't reached that loop eddy yet?
That was further south, now it's in much warmer TCHP, in the 70-90 kJ cm-2 range.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting MiamiHurricanes09:
Uh-oh.

is this shoewing the ridge weakening?
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what the hell happen to the high in that map?
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1685. centex
Quoting centex:
Other than speculation, what is up with recon? They report historical pressure for TS and put head between legs and going home?
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Quoting MiamiHurricanes09:
Uh-oh.

Miami does that show the High lifting out on the map?
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1683. centex
Other than speculation, what is up with recon? They report historical pressure for TS and put head between legs on going home?
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1682. xcool
confirmed by nhc
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Quoting MiamiHurricanes09:
Uh-oh.



is the ridge going bye-bye?
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Late Nite Update On Alex
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If I had to guess....
I would put landfall at La Pesca or just south of it.
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Quoting MiamiHurricanes09:
Uh-oh.



what??
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting BoyntonBeachFL:
Per NHC: Hurricane Hunter aircraft had a problem with their radar, so they were unable to sample the northeast quadrant of Alex. However, NHC expects to upgrade to Hurricane Alex at the 11pm advisory.


Where did you hear that?
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Uh-oh.

Member Since: September 2, 2009 Posts: 130 Comments: 21193
1674. Patrap
Man this is Phunny sometimes.

Just better than ESPN on a Mon
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I know wishcasting is fun. But come on, this ain't Wilma and it isn't September. Not gonna happen.
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Per NHC: Hurricane Hunter aircraft had a problem with their radar, so they were unable to sample the northeast quadrant of Alex. However, NHC expects to upgrade to Hurricane Alex at the 11pm advisory.
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1671. Torgen
Quoting MiamiHurricanes09:
If it is stalled Alex could do some stuff that we certainly do not want, and that's RI.


I thought he was starting to well up cooler water, and hadn't reached that loop eddy yet?
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1670. Ossqss
Quoting hurricaster:
The band of convection northeast of the storm is amazing.


Like a fuse.
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Quoting FortBendTX:
when is the ridge to Alex's north supposed to move out? anyone know?
That ridge ain't going nowhere anytime soon, well at least until another trough moves by.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
will someone answer fort bend for crying out loud
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Quoting Patrap:
00z Early Cycle NHC model tracks
Alex
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)





Dynamic Models (More sophisticated models)





Look at where they set the current intensity, 65 knots.
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Quoting TexasHurricane:
so what would it mean if Alex stalls again?


A stall usually precedes a track change but too soon for that IMO
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Alex's slow down is not good, especially if it stays slow for a while.

Link
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when is the ridge to Alex's north supposed to move out? anyone know?
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1662. will45
Quoting StSimonsIslandGAGuy:
OK who said that James Franklin said it would be a hurricane and who claimed that recon was going home?


well i clamed they were going home but not the James Franklin thingy
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Quoting kmanislander:


Looks like Alex is either stalled or moving slowly due W on 23 N 94.5 W
If it is stalled Alex could do some stuff that we certainly do not want, and that's RI.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
stall around too long and jogs south, might loop around and catch a ride with next trough
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The band of convection northeast of the storm is amazing.
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so what would it mean if Alex stalls again?
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Quoting Stormchaser2007:


I think my ears are bleeding.


It is not easy reading so much in caps.
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Quoting Ameister12:
Hurricane Alex:


Tropical Storm Marco:


The difference in size is amazing.

A true David vs. Goliath!
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1653. will45
Quoting Baltimorebirds:
will45 they want a good sleep.


someone said mechanical prob but i cant confirm
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Quoting MiamiHurricanes09:
Alex seems to have been moving towards the west but as of lately it seems as if it has slowed down considerably and could be stalled. Definitely not good if this persists.

Floater - Visible Loop


Looks like Alex is either stalled or moving slowly due W on 23 N 94.5 W
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1651. Ossqss
Interesting

Station 42055
NDBC
Location: 22.017N 94.046W
Conditions as of:
Wed, 30 Jun 2010 00:50:00 UTC
Winds: WSW (240) at 29.1 kt gusting to 36.9 kt
Significant Wave Height: 8.2 ft
Dominant Wave Period: 6 sec
Mean Wave Direction: WNW (290)
Atmospheric Pressure: 29.36 in and rising
Air Temperature: 83.1 F
Dew Point: 77.5 F
Water Temperature: 84.7 F


http://www.ndbc.noaa.gov/station_page.php?station=42055
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Quoting Baltimorebirds:
Alex would sqaush marco.Marco looks like a thunderstorm cell.Anywho what was that storm in the east pacfic at the time.

More like Absorb it & suffer the same fate as Darby.
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1648. JRRP
Quoting Ameister12:
Hurricane Alex:


Tropical Storm Marco:


The difference in size is amazing.

lol
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Quoting Stormchaser2007:
Whens the next recon?

Next one is scheduled to leave at 07:00 UTC or 3:00 AM EDT. They might just move it up because the other one had to leave early.

000
NOUS42 KNHC 281430
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1030 AM EDT MON 28 JUNE 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 29/1100Z TO 30/1100Z JUNE 2010
TCPOD NUMBER.....10-028

I. ATLANTIC REQUIREMENTS
1. TROPICAL STORM ALEX
FLIGHT ONE - NOAA 49
A. 30/0000Z
B. NOAA9 0901A ALEX
C. 29/1730Z
D. NA
E. NA
F. 41,000 TO 45,000 FT

FLIGHT TWO - TEAL 70
A. 30/0000,0300,0600Z
B. AFXXX 1001A ALEX
C. 29/2200Z
D. 23.5N 94.2W
E. 29/2330Z TO 30/0600Z
F. SFC TO 10,000 FT

FLIGHT THREE - TEAL 71
A. 30/0900,1200,1500Z
B. AFXXX 1101A ALEX
C. 30/0700Z
D. 24.1N 95.3W
E. 30/0830Z TO 30/1500Z
F. SFC TO 10,000 FT


2. SUCCEEDING DAY OUTLOOK: CONTINUE 3-HRLY FIXES.
POSSIBLE G-IV MISSION FOR 01/0000Z.

3. REMARKS: NOAA 42 WILL BE DOING RESEARCH FLIGHTS INTO
ALEX WITH TAKEOFFS EVERY 12 HRS FOR THE NEXT TWO DAYS.
(29/0800Z, 29/2000Z THROUGH 30/0800Z) OPERATING
ALTITUDE 12,000 FT.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
JWP
Member Since: September 2, 2009 Posts: 130 Comments: 21193
1646. centex
Quoting will45:

nope they heading home im thinking
Just systematically flying through quadrants, will turn around soon and head for center unless mechanical failure.
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1645. angiest
Quoting 1900hurricane:

Let's play Where's Waldo... I mean Marco!



And look, there are some storms up in the plains that could give Marco a run for his money!
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Marco was the size of now freakin Alex's CDO!!
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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.