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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1157. xcool
btwntx08 :0
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting eddye:
tropics chat plz
its not hitting south florida so you can go back to whatever you were doing.
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Storm:
How likely is it that Alex comes here? I'm starting to think that there is nothing for me to worry about.
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Storm do you think that the track will shift more to the north? .....I hope not!!..... We really don't need it any where near the oil!!
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Quoting Levi32:
No eyewall yet lol.
Yeah, still a while before any of that happens.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting smmcdavid:


And when will that be?


00z runs!
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1147. centex
Convection near center on rise and wider system tightning up. Showing signs of getting back to it's old self.
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good evening everyone...so it might look like it may go more northerly than expected...could this be true StormW?? i have been just sitting back and reading the past few days and to me i just don't see it going into mexico at all..
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1145. xcool
homelesswanderer big big ififif
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting TampaSpin:


Near the Texas / Louisiana Line.....more likely just south of there in my opinion....as at least a CAT 3 or close to it IN MY OPINON ONLY!


hmmmmm - well, I am pretty much right there. About 15 minutes from the LA border. Will definitely be watching....
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On this loop, you can watch Alex as it has rounded the southwest extent of the subtropical ridge...currently Alex is trying to make a quick run to the north. Meanwhile, the next ridge is building over the Rockies and quickly moving east, filling in the current troughiness over the mid-South. Because the base of the trough is so far north (more than 10 degrees of latitude away), the northward pull is fairly weak, so I don't expect Alex to make too much poleward progress. The trough's base looks to be over the midwest (Iowa, Illinois, Indiana area), so it's just about to pass by the longitude of Alex, leaving Alex behind:

Link
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Quoting FFEMTRQ:



For some, P.H.D. only means Piled Higher & Deeper
You're right, most of the NHC employees landed those jobs cause they got laid off from the 7-11. Its must better to trust children 3 months out of diapers or those hiding in their mom's basement thinking just cause they know how to post a map or regurgitate what they have read or heard...I feel safe now.
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Quoting barbamz:
Another non-tasked recon mission started from Florida.


Is that one of those planes that drops floats in the GOM to determine steering currents for the oil?

Or are you sure this is actually a recon?
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1137. xcool
early morn for new models dat
Member Since: September 26, 2009 Posts: 2 Comments: 15620
We in Louisiana are already feeling Alex. Been raining on and off all day!
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Quoting StormW:
We'll definitely know more when the G4 data comes out of the models.


Did you mean the storm would go directly to the north on the west side of the ridge that would take it to NOLA? I looked that's what I see. Dunno if that's right.
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Quoting RecordSeason:
Convection Injection. CDO forming. Eye wall forming.
A CDO needs to develop before an eyewall develops, so I don't think both can develop at the same time. Correct me if I'm wrong please.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
1131. xcool
MiamiHurri :)
Member Since: September 26, 2009 Posts: 2 Comments: 15620
1130. Levi32
No eyewall yet lol.
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1129. Patrap
# 1096

I just noted the Bi-lobing around the Mean center earlier USSINS..,dats all.

Its always been bigger than the Embedded CoC's that have spun out finally.

Reminds me alot of Lili and Isidore still from Late 02


Member Since: July 3, 2005 Posts: 421 Comments: 127550
1128. help4u
HWRF to Texas again. 18z
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1127. KEEPEROFTHEGATE (Mod)
01L/TS/A/CX
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Thanks. :)
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1125. Levi32
Quoting StormW:


Probably not until late tonight, or early morn.


Do they wait that long?
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I think Alex will become a major hurricane and more quickly than many think, its pressure is bordering on cat 1 on the last update.
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1123. barbamz
Another non-tasked recon mission started from Florida.
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1122. eddye
tropics chat plz
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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 meaning potentially upper TX coast..? (emphasis on "potentially" b/c I realize there are a lot of factors at play) :)
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Quoting Tazmanian:




looks like its froming a big eye
LOL, it's not forming an eye.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:




looks like its froming a big eye
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1116. Levi32
Quoting HoustonTxGal:
When can we expect the G$ data StormW?


It should be in the 0z models, which should be an interesting model cycle.
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Quoting smmcdavid:


And when will that be?


tonight
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When can we expect the G4 data StormW?
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It seems to me that Alex is doing a fine job of sucking up the lifeless remains of Darby. That should fill in any dry pockets to the West.
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Quoting StormW:
We'll definitely know more when the G4 data comes out of the models.


And when will that be?
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This reminds me. Good sale on batteries at amazon. Off to stock up on D's before 196 hours gets here. ;)
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1110. FFEMTRQ
Quoting xcool:
NHC not god & i know they got p.H.D SO WHAT.



For some, P.H.D. only means Piled Higher & Deeper
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Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting TexasHurricane:


Tampa - Where do you think this will go and possibly how strong??


Near the Texas / Louisiana Line.....more likely just south of there in my opinion....as at least a CAT 3 or close to it IN MY OPINON ONLY!
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.