Alex continues to slowly organize

By: Dr. Jeff Masters , 7:17 PM GMT on June 28, 2010

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Tropical Storm Alex continues to slowly grow more organized as it steams away from Mexico's Yucatan Peninsula. Satellite loops show that Alex's heavy thunderstorms continue to increase in areal extent, and low level spirals bands are slowly building to the south and north. The clockwise flow around an upper-level high pressure system a few hundred miles west of Alex is bringing about 15 knots of wind shear to the storm, which is slowing intensification. Heavy thunderstorm activity is limited on the storm's northwest side, thanks to the shear and some dry continental air flowing off the coast of North America. Sea Surface Temperatures are very warm, 29°C. The latest Hurricane Hunter center fix, at 12:07 pm CDT, showed a central pressures of 990 mb, a 1 mb rise in six hours. Top winds were holding steady near 60 mph. Alex has stalled out the last few hours, as it began to "feel" the trough of low pressure to its north breaking down the high pressure ridge that has been pushing the storm to the west-northwest. This stall has allowed the storm to churn up cold water from the depths, which is probably interfering with development. Satellite loops show that Alex has a very large circulation covering about 2/3 of the Gulf of Mexico. We can expect that should Alex become a Category 2 or stronger hurricane, its storm surge will affect a much wider stretch of coast than Hurricane Dolly of 2008 did.


Figure 1. Afternoon satellite image of Alex.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models have come into much better agreement. A consensus forecast arrived at by averaging together most or all of the tracks of our top models--the GFS, ECMWF, GFDL, NOGAPS, HWRF, UKMET, and GFDN--is pretty much what NHC always uses as the basis of their forecast. This consensus forecast has narrowed in on the region just south of the Texas/Mexico border as being the most likely landfall location, with the usual cone of uncertainty surrounding it. The computer model that had been making the northernmost landfall predictions, the Canadian model, is now projecting a landfall 100 miles south of the Texas/Mexico border. There has been a general southward shift of the models in their latest runs, and the most northerly landfall location, near Port Mansfield, is now being predicted by the HWRF model. The earliest landfall time is Wednesday morning, and the latest is Thursday morning. Which model should you trust? Last year, the best performing models at the 3 day forecast period were the GFS, Canadian, ECMWF, and GFDL.

With steering currents relatively weak, the uncertainty in landfall location is high. The average error in an NHC 72-hour track forecast last year was 230 miles, which is about the distance from Brownsville to Port O'Connor. Consider also that the NHC cone of uncertainty is the region where 2/3 of the time (using the last 5 years of statistics) the center of a storm will go. Forecast errors tend to be equally large along track (speed errors) and cross-track (deviations from side-to-side), so that means that about 20% of the time a storm will not be in the cone of uncertainty. Given the slow motion of Alex and the recent uncertainty of the computer models, people living just beyond the edge of the cone of uncertainty should not be confident yet that Alex will miss them.

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 10am CDT (15 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 67% chance of tropical storm conditions (winds 39+ mph), 16% 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.

La Pesco, MX: 49% tropical storm, 6% hurricane.

Tampico, MX: 31% tropical storm, 4% hurricane.

Corpus Christi, TX: 45% tropical storm, 6% hurricane.

Freeport, TX: 23% tropical storm, 2% hurricane.

Galveston, TX: 21% tropical storm, 1% hurricane.


Figure 2. Skill of computer model forecasts of Atlantic named storms during 2009. OFCL=Official NHC forecast; GFS=Global Forecast System model; GFDL=Geophysical Fluid Dynamic Laboratory model; HWRF=Hurricane Weather Research Forecasting model; NOGAPS=Navy Operational Global Prediction System model; UKMET+United Kingdom Met Office model; ECMWF=European Center for Medium Range Weather Forecasting model; CMC=Canadian GEM model; TVCN=one of the consensus models that lends together all (or most) of the above models; BAMM=Beta and Advection Model (Medium Layer.) Image credit: National Hurricane Center 2009 verification report.

Uncertainty in the NHC Cone of Uncertainty
A research project funded by NOAA known as the Joint Hurricane Testbed has produced a remarkable number of tools now in operational use at the National Hurricane Center to improve hurricane forecasts and warnings. One of these projects, called "Prediction of Consensus TC Track Forecast Error and Correctors to Improve Consensus TC Track Forecasts", was an effort by Dr. Jim Goerss at the Navy Research Lab to improve the accuracy of the NHC "cone of uncertainty" (AKA the "Cone of Death") showing where a storm is expected to track 2/3 of the time. The radius of the circles that make up the cone are based on error statistics of the official NHC forecast over the past five years. We can expect in certain situations, such as when the models are in substantial disagreement, a consensus forecast made using these models will have much greater than average errors. Since the NHC typically bases their forecast on a consensus forecast made using a combination of reliable hurricane forecasting models, it is instructive to view the "GPCE" (Goerss Prediction Consensus Error) circles to see if the uncertainty cone should be smaller or larger than usual. The consensus forecast I'll look at is called "TVCN", and is constructed by averaging the track forecasts made by most of (or all) of these models: GFS, ECMWF, NOGAPS, GFDL, HWRF, GFDN, and UKMET. In the case of this morning's 12 UTC (7am CDT) June 28 run of these models, here is what the radius of the "cone of uncertainty" should be, in nautical miles:

12 hours: 42 nm
24 hours: 73 nm
36 hours: 96 nm
48 hours: 112 nm
72 hours: 173 nm
96 hours: 327 nm
120 hours: 376 nm

And here is the radius of NHC's "cone of uncertainty" for their official forecast, based on the average errors for the past five years:

12 hours: 36 nm
24 hours: 62 nm
36 hours: 85 nm
48 hours: 108 nm
72 hours: 161 nm
96 hours: 220 nm
120 hours: 285 nm

So, the GPCE error estimates are showing that the latest forecasts for Alex out to 72 hours are 4% - 17% higher in uncertainty than average. The 4 - 5 day forecasts are 32% - 49% more uncertain than average--but of course, we expect Alex to be inland at those times.

Intensity forecast for Alex
Alex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify. Wind shear is currently a moderate 15 knots, and is projected by the SHIPS model to decrease to the low range, below 10 knots, on Tuesday and Wednesday. The combination of low wind shear and high ocean heat content should allow Alex to intensify into a hurricane. NHC is giving Alex a 78% chance of being a hurricane on Wednesday morning, and a 16% chance it will be a major hurricane at that time. Water vapor satellite images, though, show plenty of dry air over Texas and the adjoining waters, and this dry air may turn out to be a significant detriment to Alex. 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. Another factor limiting Alex's intensification may be its slow forward speed. Alex has already stalled out once, and may stall out later in its path, as well. A stalled-out storm tends to pull up cold water from the depths, limiting intensification. In short, Alex has the potential to intensify into a major hurricane, but there are enough roadblocks that I give a 20% chance of this happening.

Elsewhere in the tropics
None of the reliable computers models is calling for tropical storm formation over the the next seven days in the Atlantic.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex will not directly affect the oil slick location, other than to bring 2 - 4 foot swells to the region on Wednesday. However, because Alex is such a deep low pressure region, strong southeast winds of 15 - 25 knots will blow over the oil slick region today through Wednesday, 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.

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

Portlight continues its Haiti response
Hurricane season is here, and Haiti is not ready. Over 1.5 million Haitians are living outside in tents or under tarps, and are highly vulnerable to a hurricane. Portlight is working on constructing steel shelters out of shipping containers for homeless Haitians, as detailed in the Haitian Relief Recap blog post. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to Portlight's efforts in Haiti.


Figure 3. Still frame from the remarkable video taken inside the Haitian Presidential Palace during the 2010 earthquake.

To remind people of just how devastating the earthquake was, the Haitian government released a video earlier this month showing the inside of the Haitian Presidential Palace during the mighty Haitian earthquake.

Next post
Dr. Rob Carver is planning on making a post late tonight, and I'll have an update by 9:30am CDT on Tuesday.

Jeff Masters

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Quoting KaNaPaPiJoSa:
anyone find it odd that alex is following the CLIP? Go West Young Man, Go West!!!!

Go west young man, haven't you been told?
Mexico's full of whiskey, women and..well..mold?
Member Since: August 16, 2007 Posts: 1 Comments: 2348
2556. WxLogic
Quoting atmoaggie:

Should still get in the 00 Z GFS. Just wrapping up assimilation mode.


atmo... that quick, wow... nice to know we have some fast QA checks.
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Quoting katadman:





"And feel my finger on your outer bands..."

Howdy,Flood. I sent you a sarcastic comment earlier, but you must have gotten up to feed the cats.


Nah, I was taking the flying dog out for a little walk...got a sec? Give me a call, will you?
Member Since: August 2, 2006 Posts: 10 Comments: 9922
Quoting swlagirl:
I know what you mean, I live in swla...not nervous yet, but you never know....
I live in Gulfport MS and am getting nervous.Something about this one seems very ominous.
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Quoting SouthDadeFish:
People are freaking out way too much right now. Its just a tropical storm. Right now the NHC is only giving it a 7% chance of becoming a cat 3. Relax, its not creating its own steering currents right now.


Exactly..but that's what people do here on this blog
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Quoting StormJunkie:
GHCC site having problems tonight?


Yeah, it was down for the past hour or so. It just got working again, but it's missing imagery from 23:45-2:15 UTC.
Member Since: February 21, 2008 Posts: 1 Comments: 340
woud t it be funny if this storm this kep going N and hit LA be come that what am seeng if it dos not turn soon that where it will end up
Member Since: May 21, 2006 Posts: 5091 Comments: 115131
anyone find it odd that alex is following the CLIP? Go West Young Man, Go West!!!!
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2548. WxLogic
Quoting Levi32:
G-IV sure covered its tracks very well....anyone yet know which model runs will have this data?



I believe 06Z to 12Z should be good runs with that injected data.
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2547. scott39
Quoting Levi32:
It is possible that although waters are still shallow where Alex currently is, he has finally started moving a bit today, and he may have moved off of the cool patch he upwelled for himself further south from where he is now, and he is likely over fresh warm water up at 28-29C, shallow though it is.
Is the forecasted ridge in place with where Alex is ,to hit N MX/S TX?
Member Since: June 13, 2009 Posts: 0 Comments: 6784
GHCC site having problems tonight?
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Quoting Levi32:
G-IV sure covered its tracks very well....anyone yet know which model runs will have this data?


Should still get in the 00 Z GFS. Just wrapping up assimilation mode.

ANALYSIS 02:53:35 03:18:40 RUNNING-02:54:08 ON-TIME
Member Since: August 16, 2007 Posts: 6 Comments: 12461
2544. Levi32
Quoting StormW:


It's not August?


Bingo....lol.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
2542. Levi32
Quoting Chicklit:

Hi Levi,
Alex is lookin mighty impressive in a fairly short time.
From the Doc's blog:
Intensity forecast for Alex
Alex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify.


Yeah and it's not even over that stuff yet.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
What are the new estimates on forward speed?
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2540. Levi32
G-IV sure covered its tracks very well....anyone yet know which model runs will have this data?

Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting StormW:


It's not August?

lol good one storm but very true
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2537. Levi32
It is possible that although waters are still shallow where Alex currently is, he has finally started moving a bit today, and he may have moved off of the cool patch he upwelled for himself further south from where he is now, and he is likely over fresh warm water up at 28-29C, shallow though it is.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Evening all.

I see Alex has his sea legs back it looks like.

And on a side note...WTG Gamecocks! Great pitching tonight, now we just need to wrap it up tomorrow night. No need to let it go to three.
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2535. bappit
Quoting MiamiHurricanes09:
That's a bad comparison. You can't compare a tropical storm to the strongest hurricane ever.

I agree.
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Quoting MZV:
I'm getting the impression this is going to be a Frances-like experience wherever it lands. Big, slow moving storm that feels like it takes 2 or 3 days to clear out.


God I hope not. I rode Frances (and Jean) out in Okeechobee FL. I was stuck in the house for two full days. Now I live in SW Texas and the damn storms are still chasing me!
We had 2.6 inches of rain today, not associated with Alex. More rain predicted for tomorrow and then maybe Thursday and Friday heavy rain from Alex. Its beginning to make me concerned about flooding all along the Rio Grande middle and lower valley.
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2533. scott39
Quoting StormW:


No...for his current steering, you use the 500-850...but since strengthening is forecast, you want to go one layer up to see what's potentially gonna happen.
Storm would please look at post 2494
Member Since: June 13, 2009 Posts: 0 Comments: 6784
Quoting Levi32:
Good evening all. Alex appears to be undergoing steady intensification, and while still over the shallow shelf waters of the Yucatan too...it hasn't even hit the higher TCHP yet.

Hi Levi,
Alex is lookin mighty impressive in a fairly short time.
From the Doc's blog:
Intensity forecast for Alex
Alex is currently over a region of ocean with relatively low total ocean heat content (about 10 - 30 kJ/cm^2). By Tuesday and Wednesday, the heat content will increase to 40 - 70 kJ/cm^2, which is high enough to allow Alex to rapidly intensify.
Member Since: Posts: Comments:
.
Member Since: February 21, 2008 Posts: 1 Comments: 340
2530. WxLogic
Quoting Levi32:
Good evening all. Alex appears to be undergoing stead intensification, and while still over the shallow shelf waters of the Yucatan too...it hasn't even hit the higher TCHP yet.


Good evening... might be a long night for you. :)
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2528. bappit
Quoting SouthDadeFish:
People are freaking out way too much right now. Its just a tropical storm. Right now the NHC is only giving it a 7% chance of becoming a cat 3. Relax, its not creating its own steering currents right now.

Good point.
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Quoting MiamiHurricanes09:

hwo many inches per hour 09 cuz that alot of water content
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Quoting RecordSeason:
2435:

You sir are ridiculously wrong.

Sad really.
Ridiculously wrong about how a hurricane functions? Seriously? And you are sad about something, apparently...

To all:
Hokay, y'all make sure you get every last word from the kiddie that refuses to try to listen or learn about how hurricanes work. Enjoy your evacuation.

I just want to say this. Do not let this one ruin your impression of some of our young posters. Not all of them are posers. We have some youngsters that know a lot and a few others that are convinced they know everything, yet refuse to learn anything, that give all the rest a bad name.

This one believes there is a great conspiracy at play to un-fear everything. From his temp obs showing the real temperature and all of the official obs showing 8 degrees less, his barometer is 6 mb lower that any official, conspirator's observation (a sign that Alex is coming to LA, according to him), and a hurricane is going to retrain it's strength because a rainband it still over water..., oh yeah, and the NHC is conducting a ploy to make sure no one knows that Alex is going to make landfall in LS, MS, AL, FL, and the UK.

I'll be hitting the minus on the rest of Mr Minus's posts in hope that no lurker makes the mistake of trying to get good info from the worst of wrong places. Join?
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting bappit:

I vote for a big weather pattern with a tropical storm embedded in it.


I agree. It's been raining in San Antonio, but the rain is from an unrelated low pressure system.
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Quoting Grothar:
We are currently getting hammered with some stong rain and gusty winds in Ft. Lauderdale right now. Those outer bands must have some energy in them.


Been getting hammered here off and on all day too. Its quite amazing considering how far away this storm is.
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Quoting Tazmanian:
am i talking to a window how many times do i have too tell you guys youdo not need heat potential for a cat 4 or 5 storm this look at are past storm in the E pac it did not have any heat potential at all but still got up too cat 5


Is that you, God?
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Quoting Levi32:
Good evening all. Alex appears to be undergoing stead intensification, and while still over the shallow shelf waters of the Yucatan too...it hasn't even hit the higher TCHP yet.

levi ok whats the good news if there is any
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2520. leo305
the thing is still well to the N/NE of the model runs..
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NWS yet to update Texas cost with Hurricane Warning.

Member Since: May 27, 2009 Posts: 0 Comments: 4438
2518. Levi32
Good evening all. Alex appears to be undergoing stead intensification, and while still over the shallow shelf waters of the Yucatan too...it hasn't even hit the higher TCHP yet.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting MiamiHurricanes09:
CDO beginning to develop.


those are some cold cold cold chilly cold tops
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2515. Grothar
We are currently getting hammered with some stong rain and gusty winds in Ft. Lauderdale right now. Those outer bands must have some energy in them.

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Quoting alaina1085:
Ok Alex, you can take that west turn anytime now.... Gettin nervous here in SELA.
I know what you mean, I live in swla...not nervous yet, but you never know....
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People are freaking out way too much right now. Its just a tropical storm. Right now the NHC is only giving it a 7% chance of becoming a cat 3. Relax, its not creating its own steering currents right now.
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2512. bappit


Okay, the yellow (an red) area on this map is Alex.
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2511. JLPR2
Quoting twooks:


Was it? :x err Stepbrother :P


haha! XD
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10:00 PM CDT Mon Jun 28
Location: 21.0°N 91.6°W
Max sustained: 65 mph
Moving: N at 5 mph
Min pressure: 985 mb
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CDO beginning to develop.

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Quoting StormW:


I guess Alex is starting to MOOOOOve!


That was a good one Storm !
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Quoting guygee:

"When I hold you in my spiral bands..."


Quoting guygee:

"When I hold you in my spiral bands..."



"And feel my finger on your outer bands..."

Howdy,Flood. I sent you a sarcastic comment earlier, but you must have gotten up to feed the cats.
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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.