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 hydrus:
What happened? It looks like a poster from the 60,s.


Yeah, 1968, (I think???) LOL
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Just making the observation that the upwelling issue in shallow waters, and, dry air entrainment from the NW of Alex is really causing him some problems in the short-term which includ the lack of significant convection near the COC.....That may certainly change over time but Alex having a tough time right now me thinks.
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.


I dunno, if it was working, I wouldn't have been able to enjoy that cool overlay they use instead.
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Quoting Patrap:


I gotz to say..maybe.

Just maybe were seeing the reformation process begin as that older CoC is toast points.

Note the Older Coc lose out


Why are you *still* posting IR? IR is *not* useful for finding COCs. That's what vis (and esp. RGB) is for.

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Quoting KarenRei:
Bad looking? Pitiful? Am I the only one watching this massive convection building toward the COC? If this keeps up, that dry air won't be able to stop him from building up a nice CDO.

A storm's health is not its feeder bands. It's its center. This storm has a borderline Cat 1 central pressure and solid circulation visible on RGB, but not much of a CDO due to dry air. That is looking to be remedied later this evening.


Your avatar is sooooo cool, but Alex is not going to be a GOM factor. More to come though.
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Quoting MrNatural:
Alex is very clearly developing an eyewall on the north side.


its had a ragged one for awhile now, its got to get the convection over the coc to really build it back.
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A slice from another model movie.



and the wave model movie

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Quoting StormChaser81:


Just take the right drugs and it will clear up.


LOL!!!
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249. Skyepony (Mod)
Quoting hurricanehanna:

okay, now MIMIC makes it look as though it is heading due North....


The last few frames hints to a wobble NW but yeah.. & takes away alot of confusion of where the storm's center is for ya'll looking at IR.. I couldn't get the several most recent frames to come up on the RGB loop either, so MIMIC was a big surprise.
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.



Its the Technicolor Hurricane!
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Quoting Baltimorebirds:
Those thunderstorms are apart of alex.I gon't think it will spin anything up of it's own.


i was told that it's an outflow breaking away from alex. it will fizzle out eventually.
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Quoting MrNatural:
Alex is very clearly developing an eyewall on the north side.
It certainly is a possibility considering it is near hurricane strength. But it has long ways before an eye develops.
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It's pretty clear He ain't movin much.Link
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.



I know Jimmy Stewart wouldn't have liked it.
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Quoting hurricanehanna:

okay, now MIMIC makes it look as though it is heading due North....


yeah it does....who knows though. Maybe the models will start to change again. I guess we will see...
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Quoting hurricanejunky:
Spoke to CycloneOz just now. He's looking for a go / no-go for a Brownsville,TX landfall and storm chase deployment. He's got to leave soon if he's going. All advice and insight welcome either on here, my blog or via WUmail.

Also, any Brownsville residents please contact me via my blog or WUmail as I need some help from you.


It needs to get it act together, Cat 1 isnt worth chasing. will weaken probably pretty quickly during landfall and then you just in a TS.
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Quoting RecordSeason:
Patrap, the swirly vortex is still in the exact same spot, and is still the CoC.

The thing you are looking at is an outdated graphic first of all, and secondly is clearly just a "really strong" feeder band.

Again, it is being absorbed by the CoC as latest visible and infrared show.


I gotz to say..maybe.

Just maybe were seeing the reformation process begin as that older CoC is toast points.

Floater - Rainbow Color Infrared Loop
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Alex is very clearly developing an eyewall on the north side.
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This is the NAM and should be taken with a grain of salt except for troughs and ridges. The ridge is still located really far to the north at 54 hours. The one that kept Allen from turning north was centered over Arkansas. The one that turned Bret just north of Brownsville was centered over Arkansas. This one isn't close to there.

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The center is pretty darn obvious on visible / RGB :v

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Quoting ShenValleyFlyFish:


Post verifiable links for any assertions made at this point. From here on in this becomes a science based discussion, not an opinion board or social forum. Applies to all, me included.


Good luck with that, outside of the externally linked data, 90% of this and any other blog on the web is opinion.
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.

What happened? It looks like a poster from the 60,s.
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231. Skyepony (Mod)
Quoting RecordSeason:
162:

Maybe you should try looking at the entire structure.

Alex eats Darby


Poor Darby. Such a cute little fish storm. Guess this effectively cancels the dance the models had called for..where Darby moves right while Alex goes left.
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Quoting NOLALawyer:
Nasty weather moving through NOLA right now.
yeah tell me about it...I just got stuck on top of the Huey P....I mean the very top...
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.



Whoa, what was in that candy bar I just ate :/
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Quoting KarenRei:


Let's all say it together: "You Don't Use IR To Find The COC."

Use RGB. The center is clear as day, right where it was. It's not even challenging, since the storm is still rebuilding its CDO. Which it's looking like may happen by this evening.

Furthermore, hurricane-pressure COCs don't just jump a great distance away. This line of discussion makes no sense.

Looks stalled if you ask me.
Member Since: July 29, 2006 Posts: 28 Comments: 1777
Quoting Skyepony:
Check out Alex on MIMIC

okay, now MIMIC makes it look as though it is heading due North....
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Quoting Patrap:


Im looking at the convective Based Expansion.



Im well aware where the RGB and VIZ to Night IR channels can show, Mom.

Thanx,..is my Mac and cheese ready yet?





You don't use convective bursts to find the COC; by definition, those are high altitude. You use the low-level cumulus clouds. They very clearly show the same COC as ever. This storm actually has a beautiful low level cyclonic flow, reaching all the way out to Darby, as another poster recently noted. It's about as far from a center relocation as you can get. I have no clue where you're getting this notion from.
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Spoke to CycloneOz just now. He's looking for a go / no-go for a Brownsville,TX landfall and storm chase deployment. He's got to leave soon if he's going. All advice and insight welcome either on here, my blog or via WUmail.

Also, any Brownsville residents please contact me via my blog or WUmail as I need some help from you.
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Quoting Levi32:
Don't you wish this radar had been working these last couple days.



Just take the right drugs and it will clear up.
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Quoting mtyweatherfan90:


During the last frames is moving again to the NW.


yes. i love the MIMIC it makes things so much easier.
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Don't you wish this radar had been working these last couple days.

Member Since: November 24, 2005 Posts: 635 Comments: 26547
Quoting KarenRei:
Bad looking? Pitiful? Am I the only one watching this massive convection building toward the COC? If this keeps up, that dry air won't be able to stop him from building up a nice CDO.

A storm's health is not its feeder bands. It's its center. This storm has a borderline Cat 1 central pressure and solid circulation visible on RGB, but not much of a CDO due to dry air. That is looking to be remedied later this evening.


I do see some convection to the SE of the center that appears to building N and W. Time will tell if it's just a burst of convection or an increase in organized convection.
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Nasty weather moving through NOLA right now.
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Quoting Skyepony:
Check out Alex on MIMIC
Cool loop. Looks like it is moving due north.
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Quoting Patrap:


Im looking at the convective Based Expansion.



Im well aware where the RGB and VIZ to Night IR channels can show, Mom.

Thanx,..is my Mac and cheese ready yet?





That expansion is due to the warmer SSTs to the north, enhancing convection away from Alex's center, which is currently over upwelled colder water. That's not evidence of a center reformation. The convection is just forming where it can, and right now the only place it really can go is well north of Alex's center.
Member Since: November 24, 2005 Posts: 635 Comments: 26547
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Quoting truecajun:
all right come on all you smart weather people. please explain to me what is smack dab in the middle of the gulf. is this part of alex or not? is it possible that it could spin up it's own center? i certainly hope not. i'm just wondering.
Wondering the same thing..
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thankyou levi. we did have some nasty weather earlier. yesterday was bad too.
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Quoting Baltimorebirds:
It was jim willams,Tom K. at the nhc,and joe bastardi.


Post verifiable links for any assertions made at this point. From here on in this becomes a science based discussion, not an opinion board or social forum. Applies to all, me included.
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Quoting Skyepony:
Check out Alex on MIMIC


During the last frames is moving again to the NW.
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Quoting Hurricanes101:
I have been seeing people say outflow boundary when I think they mean outer feeder band

there is a difference


I've been using outflow boundary and the difference is a feeder band moves back into the storm system and a outflow boundary keeps moving away not aiding the storm in energy.
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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.