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 Levi32:


I thought it was :)

Ended up with an A....probably won't be so lucky in the next level up.


Gotta be kidding me. OPEN BOOK. Haven't had one of those since middle school...
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That's not right Levi...That's the professor I need...Open book!

Ok, night all. See everyone, and Alex tomorrow.

And atmo, don't trust that xtrap model...It's real unreliable from what I hear...lmao
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2854. xcool
sarahjola he nnw now
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2852. Levi32
Quoting atmoaggie:
No fair!


I thought it was :)

Managed to make it out with an A....probably won't be so lucky in the next level up.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
gfs para model takes north mexico....
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Quoting Levi32:


Ah no I have experienced the terrors of my first college stat class....thank the good Lord all the tests were open-book.
No fair!
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Quoting Headindaclouds:
"The butterfly effect is a metaphor that encapsulates the concept of sensitive dependence on initial conditions in chaos theory; namely that small differences in the initial condition of a dynamical system may produce large variations in the long term behavior of the system. Although this may appear to be an esoteric and unusual behavior, it is exhibited by very simple systems: for example, a ball placed at the crest of a hill might roll into any of several valleys depending on slight differences in initial position. The butterfly effect is a common trope in fiction when presenting scenarios involving time travel and with 'what if' scenarios where one storyline diverges at the moment of a seemingly minor event resulting in two significantly different outcomes."
Now look up Ed Lorenz...
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Quoting Levi32:


Nvm here's 0z.



Levi, could you help me? how do i get the TS symbol and models into google earth with the HH info?
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2847. Patrap
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2846. Levi32
Quoting StormJunkie:


Come on, it's just a hop, skip, and a jump right? ...Not to mention your taking Calculus if I remember correctly...So Prob & Stats should be a cake walk.

Thanks for the moral support atmo ;)


Ah no I have experienced the terrors of my first college stat class....I thank the good Lord all the tests were open-book.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
"The butterfly effect is a metaphor that encapsulates the concept of sensitive dependence on initial conditions in chaos theory; namely that small differences in the initial condition of a dynamical system may produce large variations in the long term behavior of the system. Although this may appear to be an esoteric and unusual behavior, it is exhibited by very simple systems: for example, a ball placed at the crest of a hill might roll into any of several valleys depending on slight differences in initial position. The butterfly effect is a common trope in fiction when presenting scenarios involving time travel and with 'what if' scenarios where one storyline diverges at the moment of a seemingly minor event resulting in two significantly different outcomes."
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Quoting MiamiHurricanes09:
*Yawn* Goodnight all!


Night! Thanks for the insight today. :)
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Quoting CaneAddict:


Yeah JFV has heard it before.


Hi cane- got any updates?
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Quoting wunderkidcayman:
so guys when will we have 95L any guesses where will it be and coming from


look at the african coast, nuff said!
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XTRAP -> Extrapolation
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Quoting BahaHurican:
Even NHC thinks the NHC forecast is too low....


I'm curious as to why the intensity forecast is so low, landfall isn't forecasted for almost 48 hours yet cat one status is supposed to be maintained the entire time. I don't see any real inhibiting factors in the next 2 days for Alex.
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Quoting xcool:
NOAA G-IV not all dat was put in models i just find out .
Alex has been taking a nne jog all day and even early this morning. i am wondering why they would not take in the n or nne movement that has been happening for a while, but take in any jog to the west immediately. if that makes any sense.:)
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Quoting drg0dOwnCountry:

Let's not forget about methane (natural gas).


I doubt that would significantly alter intensity, as well.
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*Yawn* Goodnight all!
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting KoritheMan:


The oil slick will not have an appreciable effect on intensity.

Let's not forget about methane (natural gas).
Member Since: September 22, 2005 Posts: 11 Comments: 2032
2832. ssmate
Quoting iluvjess:
Well CNN just cleared it all up for us. Alex will make landfall around 2:00 AM Thursday just South of Brownsville...
8 hours lurking on this sight and they just put the results on TV? I am the World's Biggest Idiot.
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Quoting StormJunkie:


Come on, it's just a hop, skip, and a jump right? ...Not to mention your taking Calculus if I remember correctly...So Prob & Stats should be a cake walk.

Thanks for the moral support atmo ;)
*snark*
I aced calculus....hated Stat...best of luck, SJ.
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Quoting BahaHurican:
Even NHC thinks the NHC forecast is too low....


Then why haven't they raised it more north?
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2829. Levi32
Quoting Levi32:


Those 0z model initializations there?


Nvm here's 0z.

Member Since: November 24, 2005 Posts: 635 Comments: 26698
Quoting Orcasystems:
I still say Northerly when you average it.



AOI


hey orca, would you mind telling me how to get the tropical storm symbol on google earth with the models? thanks in advance.
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Quoting MiamiHurricanes09:
Yeah I'll just take the 42 knot surface winds they reported.


That at the center?
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Quoting Levi32:


Oooh....um...I actually have plans on Wednesday, sorry.


Come on, it's just a hop, skip, and a jump right? ...Not to mention your taking Calculus if I remember correctly...So Prob & Stats should be a cake walk.

Thanks for the moral support atmo ;)
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Quoting AllStar17:
Good night. I wonder what Alex will look like in the morning. I strongly believe that Alex will get stronger than the current NHC forecast of 90 mph. I think that forecast is too low.
Even NHC thinks the NHC forecast is too low....
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Quoting iluvjess:
Well CNN just cleared it all up for us. Alex will make landfall around 2:00 AM Thursday just South of Brownsville...

What a relief! [Hand across brow] All this suspense was killing me. LOL
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2823. Levi32
Quoting Orcasystems:
I still say Northerly when you average it.



AOI


Those 0z model initializations there?
Member Since: November 24, 2005 Posts: 635 Comments: 26698
Quoting atmoaggie:
Like he hasn't been told that 30,382 times...


Yeah JFV has heard it before.
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Ok all I'm off for the night...I think we will have Hurricane Alex by 3 or 4 in the AM.... Now everyone play nice and you big kids play with the little kids....

while I run,run far away :o)

Taco :o)
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Quoting atmoaggie:
Like he hasn't been told that 30,382 times...


I know. I was mainly clearing it up for others, though.
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2819. Levi32
Quoting StormJunkie:
Night tc, I'm headed there before long myself! Especially since I have a Prob & Stat exam on Wed...Levi, you there...Wanna swing by and take that for me ;)


Oooh....um...I actually have plans on Wednesday, sorry.
Member Since: November 24, 2005 Posts: 635 Comments: 26698
Well, it's after midnight here, so it's bedtime for Baha.... lol

I may even get up at 5 a.m. to see what's the latest on Alex. (not guaranteeing that, though - since school has closed here, traffic is much lighter, so I can actually leave for work at 7:15 instead of 6:30 a.m...... :o)

Good night to all!
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Quoting iluvjess:
Well CNN just cleared it all up for us. Alex will make landfall around 2:00 AM Thursday just South of Brownsville...


Yeah, no more model watching. It has been solved...
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Quoting ElConando:


60mph? Perhaps another pass is needed.
Yeah I'll just take the 42 knot surface winds they reported.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Member Since: September 22, 2005 Posts: 11 Comments: 2032
Quoting KoritheMan:


XTRAP is not a model. It is just a demonstration of what would happen were the storm to continue on its present heading.
Like he hasn't been told that 30,382 times...
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Quoting Orcasystems:
I still say Northerly when you average it.



AOI
It's north of all the models, pretty interesting although rather insignificant.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
Again those are flight level. What you have to look at is the flight level winds (68 knots) and translate it to surface winds (about 51 knots).


60mph? Perhaps another pass is needed.
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Quoting GlobalWarming:


Why is the Xtrap model taking it towards Houma, La? Gulp, :(.


Houma? You mean people actually came back?...Had a guy in Baton Rouge tell me after Gustav that "dey aint comin back"
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Quoting Orcasystems:
I still say Northerly when you average it.



AOI


Yes. That is very true.
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Quoting StormJunkie:
Night tc, I'm headed there before long myself! Especially since I have a Prob & Stat exam on Wed...Levi, you there...Wanna swing by and take that for me ;)
Yeesh. Enjoy that. I limped my way through that class once and that was enough, thanks.
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Good night. I wonder what Alex will look like in the morning. I strongly believe that Alex will get stronger than the current NHC forecast of 90 mph. I think that forecast is too low.
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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.

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