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 StormW:


NHC

them boys are pacing around right now
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Quoting StormW:


NHC


lol and the poor folks that get hit! :(
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Quoting Levi32:
Guys.....what....1 hour of perhaps 6mph northerly movement is not a significant deviation from the NHC track. Give it time....if the long-term motion is well north of the NHC track then it will be significant. Rapid-scan imagery is addicting with images every 10 minutes but storms in weak steering currents wobble all over the place. Have patience before saying "Houston we have a problem".


HOUSTON YOU ARE OK, BUT "LOUISIANA WE HAVE A PROBLEM"!! just sayin
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Quoting Patrap:
Alex out the Yucatan Bunker after that sand stall..

He looks ready and now hes reaching for the,..looks Like a 9 iron..


Hmmm, this is going to be interesting..



Is he going to splice or hook??
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I know how serious this storm could/can be, but this whole scenario reminds me of the GPS in the car. When you make an unexpected or early/late change of direction you always hear "Recalculating"
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Quoting xcool:
btwntx08 hi homelesswanderer hi friends


Hi xcool. Good evening.:)
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Quoting skepticall2:


September 11th see you in the shoe since it is not on the coast or near the coast I don't think a storm will rip it down.
Lol, guess you will...
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1050. Levi32
18z GFS parallel....very nasty storm just south of the TX/MX border. 66 hours.

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1049. Patrap
Member Since: July 3, 2005 Posts: 420 Comments: 127536
what the heck? I check in at the last advisory and NHC went south on their forecast and now things have changed? I have a headache with all this flip-flop stuff. I don't know what to believe!
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1046. leo305
Quoting DestinJeff:
can that trof out west slip under the central us ridge? is that atmospherically possible, because it looks to be digging much deeper than the high is setting up

i am concerned that without landfall the sw winds out in front of that western trof may cause bad juju in the GOM


that upper level low over the bahamas is starting to reach the surface.. It may end up being a player
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1045. xcool
Joanie38 go to page 19 ..
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1044. USSINS
As Alex intensifies this evening it will get a natural, 1 or 2 degree poleward coriolis bump - regardless of steering.
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1042. Patrap
Alex out the Yucatan Bunker after that sand stall..

He looks ready and now hes reaching for the,..looks Like a 9 iron..


Hmmm, this is going to be interesting..

Member Since: July 3, 2005 Posts: 420 Comments: 127536
Quoting StormW:


No...I just looked at satellite loop imagery and he is moving due north at the moment.
It could be an allusion because the convection firing to the east of the COC makes it look like it is moving that way when it really isn't. Solid N motion seems what is happening right now, albeit slow.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
18Z Parallel GFS, Carolina on my mind


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Quoting StormW:


NHC


Good answer!!
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Quoting xcool:
we have a big problem now ...wt---


What's wrong xcool
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Quoting skepticall2:


Do you really like Miami?? J.k I know you do so don't hate on me just cause of my team this year haha keep up the good work.
LOL! Well get them Buckeyes, you'll see...
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting StormW:


If he speeds up and that weakness stays for a while, he won't
Quoting StormW:


If he speeds up and that weakness stays for a while, he won't

Hey Storm,
Any chance us swfloridians need to worry about this lil swirl off the east coast dumpin some needed rain on us? Thanks in advance!
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1034. xcool
btwntx08 hi homelesswanderer hi friends
Member Since: September 26, 2009 Posts: 2 Comments: 15620
I have elderly famly that will need to be evacuated from the TX coast so I am sitting on pins and needles here..ugh
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1031. Patrap
18z Early Cycle NHC model tracks
Alex
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)




Dynamic Models (More sophisticated models)


Early Model Wind Forecasts

Member Since: July 3, 2005 Posts: 420 Comments: 127536
1030. hydrus
Quoting StormW:


Take a look closely at that ridge.
This storm is beginning to alter the weather patterns that usually controls there movement and direction.jmo
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1029. xcool
we have a big problem now ...wt---
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1028. USSINS
Quoting TampaSpin:
We are gonna have a MAJOR HURRICANE coming IMO gang.....its coming! BE PREPARED!


B I N G O!
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Quoting TampaSpin:
We are gonna have a MAJOR HURRICANE coming IMO gang.....its coming! BE PREPARED!
Could be if the ridge doesn't build back in.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1025. Patrap
Climo rules da roost ..

..as History and the Clip Series are flirting with it.
Member Since: July 3, 2005 Posts: 420 Comments: 127536
Quoting StormW:


I believe so...however I don't think it was forecast to be that large. I've been watching out west, and the ridge appeared as if it would build in farther south and stronger...when you're watching water vapor, it's hard to determine sometimes, until hours pass and ya get to see how things are evolving. If that's all the ridge there is going to be, then there's gonna be a problem.


A problem for who??
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1023. leo305
Quoting btwntx08:

just a wobble i see a nnw right now


I definately don't see any westward component at the moment
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Quoting HoustonTxGal:
Please.. someone fill me in on where Alex is headed now. I was afk for a little while.


I've been here and I still don't know where they're talking about.
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1021. USSINS
Quoting StormW:


I believe so...however I don't think it was forecast to be that large. I've been watching out west, and the ridge appeared as if it would build in farther south and stronger...when you're watching water vapor, it's hard to determine sometimes, until hours pass and ya get to see how things are evolving. If that's all the ridge there is going to be, then there's gonna be a problem.



Thank you - finally, pointed towards an obvious alternate outcome.
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Houston we have a problem!
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Quoting MiamiHurricanes09:

Looks like it is an allusion because of convection building on the eastern side giving the impression of NE motion, but to me Alex just seems to be spinning around in place.


I guess it was just a tricky visible lol, although I don't think it's following the forecast points.
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You know I actually miss Dr.Lyons on TWC , he used to always say you can tell mostly where a storm/hurricane will track if you just follow the moisture or bands from it , nowhere does these bands go anywhere near Mexico, I said it before and I'll say it again, I could be completely wrong (usually I am):) Alex will make landfall anywhere from La to the big bend in Florida.
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1015. xcool
trough moving in tampspin help me out sir... ??????
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1014. KEEPEROFTHEGATE (Mod)
Quoting kuppenskup:
For the people in the path of this storm let's hope and pray there is no rapid intensification here.

round
round
round it goes
where it stops
nobody knows
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Quoting Levi32:
Guys.....what....1 hour of perhaps 6mph northerly movement is not a significant deviation from the NHC track. Give it time....if the long-term motion is well north of the NHC track then it will be significant. Rapid-scan imagery is addicting with images every 10 minutes but storms in weak steering currents wobble all over the place. Patience before saying "Houston we have a problem".
Yeah rapid-scan is addicting, I go back every 7 minutes and update it. Lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
We are gonna have a MAJOR HURRICANE coming IMO gang.....its coming! BE PREPARED!
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Local met here in CC sticking with TX/MX...sounds like he will go a bit farther north. Last few frames show some big expansion, she's getting bigger, ladies and gents.
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How long before the models pick up on the weakness in the ridge as well as the errors they have on timing?
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Please.. someone fill me in on where Alex is headed now. I was afk for a little while.
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1007. Levi32
Guys.....what....1 hour of perhaps 6mph northerly movement is not a significant deviation from the NHC track. Give it time....if the long-term motion is well north of the NHC track then it will be significant. Rapid-scan imagery is addicting with images every 10 minutes but storms in weak steering currents wobble all over the place. Have patience before saying "Houston we have a problem".
Member Since: Posts: Comments:

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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.