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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Hurray! G-IV NOAA 49 in the air dropping loads of dropsondes over the gulf. 0z runs should hopefully have this new data in them.

Latest drop at 25.9N 88W is showing SSE winds from the 700mb level upward until they turn SW in Alex's outflow. This is indicating the weakness in the ridge and mid-level steering currents that are trying to take the storm NNW.

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1011mb (29.85 inHg) Sea Level (Surface) 26.0°C (78.8°F) 25.6°C (78.1°F) 65° (from the ENE) 19 knots (22 mph)
1000mb 96m (315 ft) 25.2°C (77.4°F) 24.9°C (76.8°F) 70° (from the ENE) 20 knots (23 mph)
925mb 781m (2,562 ft) 21.8°C (71.2°F) 20.3°C (68.5°F) 95° (from the E) 20 knots (23 mph)
850mb 1,514m (4,967 ft) 18.0°C (64.4°F) 16.3°C (61.3°F) 115° (from the ESE) 17 knots (20 mph)
700mb 3,154m (10,348 ft) 9.0°C (48.2°F) 8.2°C (46.8°F) 155° (from the SSE) 22 knots (25 mph)
500mb 5,880m (19,291 ft) -4.3°C (24.3°F) -5.3°C (22.5°F) 155° (from the SSE) 26 knots (30 mph)
400mb 7,610m (24,967 ft) -13.5°C (7.7°F) -15.4°C (4.3°F) 160° (from the SSE) 25 knots (29 mph)

300mb 9,740m (31,955 ft) -27.5°C (-17.5°F) -30.6°C (-23.1°F) 195° (from the SSW) 13 knots (15 mph)
250mb 11,030m (36,188 ft) -37.5°C (-35.5°F) -41.0°C (-41.8°F) 225° (from the SW) 15 knots (17 mph)
200mb 12,520m (41,076 ft) -50.3°C (-58.5°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 240° (from the WSW) 15 knots (17 mph)
150mb 14,350m (47,080 ft) Height extrapolated since sonde was released within 25mbs below this level.


Member Since: November 24, 2005 Posts: 635 Comments: 26661
Floater - Rainbow Color Infrared Loop
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If its going to Northern MX or Brownsville it better be a strong ridge pushing it like that, because like one guy said, it aint as strong as the ones that pushed Allen in back in 80
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.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Thank you for that answer sky, I will read more on this
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Quoting Tazmanian:



i see you are looking for a 24hr banned i would re move that if i where you

Really? I've seen MUCH worse on here..but, sure, if you think so...it's down...lol
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StormW - is that Barometer Bob Special show at 8pm eastern tonight?
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Hello fellow bloggers..:) I guess SWLA is in the CLEAR!!! :)
Member Since: June 16, 2008 Posts: 0 Comments: 507
Quoting swlagirl:
Any chance it might take a more northerly route and hit Tx/La border?


Looks slim now but if i lived anywhere on the Gulf Coast i would keep an eye on the progress.Weird things have happened with these storms.
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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

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I figured you'd get a kick out of that Amy:-)
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Nash, you kill me.......

;)
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Quoting TexasHurricane:
I wish it would just hurry and decide what it is going to do. All this back and forth and it just sitting there is just frustrating......


T.S. Storms don't have minds of their own...they're steered by the mid level winds. Alex is heading to N. Mexico.
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Quoting RitaEvac:


Between Houston and Galveston
Looks like you'll be safe from Alex, but there is still a lot of uncertainty.

Quick question, this blog is going really slow and I went to the previous entry and everyone is posting there. What's going on?
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Quoting hcubed:
Looks like we're in for another bad spell of whether in SFLA...
Why? What will happen in South Florida?
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Quoting GlobalWarming:
My sincere apologies, blog administrators, :(.

I see you've been busy JFVing it up today, GW!!!
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Models pretty much all south now.
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Quoting muddertracker:
Wow! Nothing like a jfv/stormTOP sighting to clear out the blog! Remember: Have your trolls spayed or neutered!





i see you are looking for a 24hr banned i would re move that if i where you
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Quoting MiamiHurricanes09:
Where are you located?


Between Houston and Galveston
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Any chance it might take a more northerly route and hit Tx/La border?
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Quoting Tazmanian:




even if a storm is a cat 5???


oh hell no, I'd be freaking out
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my post form the last blog:the cloud pattern in the NE GOM is looking like a inverted trough of low pressure in the mid levels,I wonder if it could close off and work down to the surface???
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Taz read update.Weaker storm.
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Amy- Mail.
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??
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Quoting RitaEvac:
I'm getting to the point where I dont care much anymore, gonna do what its gonna do. Not running from it anyway.
Where are you located?
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Quoting RitaEvac:
I'm getting to the point where I dont care much anymore, gonna do what its gonna do. Not running from it anyway.




even if a storm is a cat 5???
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Quoting Daveg:
Sorry for the re-post, think my post got lost in all the talk earlier.

So, I would assume with the models bouncing north and south, and north and south. That anyone in northern Mexico and southern Texas should stay tuned, correct?

And is it due to the uncertainty in Alex's speed?

(noob here, trying to learn) :-)
Yes south Texas is still in the cone. On the models part you usually will see them jumping around a bit besause of the conditions of this storm.
EM>
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Last update killed the blog.
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I'm getting to the point where I dont care much anymore, gonna do what its gonna do. Not running from it anyway.
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68. Skyepony (Mod)
Quoting bassis:
What do the yellow arrows in the ascat designate


If you click the pic it goes to the source, here is the description below (in case your at work or something). I don't see yellow, you mean orange?

This picture shows the scatterometer winds (in arrows or flags), with an infrared satellite image (from METEOSAT, GOES or GMS) and numerical weather prediction model winds (currently only HIRLAM forecast in the Northern Atlantic region, in blue arrows or flags) as well as an indicative ice mask (in blue) on the background.

A wind flag is represented by barbs and solid pennants, a full barb representing a wind speed of 5 m/s, a half barb representing a wind speed of 2.5 m/s, and a pennant representing a wind speed of 25 m/s. A calm indicator circle is plotted if the wind speed is less than 0.5 m/s.

The exact data acquisition time is plotted in red next to the satellite swath.

A magenta marker on top of the wind arrow denotes land or ice presence. Orange wind arrows indicate that the Variational Quality Control flag is set, i.e. the Wind Vector Cell is spatially inconsistent. An orange dot means that the KNMI Quality Control Flag is set. More information on the quality flags can be obtained from the ASCAT Wind Product User Manual.
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Lots if moisture training towards the panhandle. I think I can safely turn off the sprinklers for a few days.
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This will be a good bouy to watch :)

Station 42055
NDBC
Location: 22.017N 94.046W
Conditions as of:
Mon, 28 Jun 2010 18:50:00 UTC
Winds: ENE (70°) at 21.4 kt gusting to 25.3 kt
Significant Wave Height: 6.6 ft
Dominant Wave Period: 8 sec
Mean Wave Direction: E (86°)
Atmospheric Pressure: 29.65 in and falling
Air Temperature: 80.1 F
Dew Point: 75.6 F
Water Temperature: 85.6 F

http://www.ndbc.noaa.gov/station_page.php?station=42055
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So you think it will have a more northern landfall?
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Looks like we're in for another bad spell of whether in SFLA...
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Quoting TexasHurricane:
I wish it would just hurry and decide what it is going to do. All this back and forth and it just sitting there is just frustrating......

isn't it always this way? I remember this with Dolly, Ike, Rita, the back & forth predictions
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The thing that bothers me about the model runs is looking at historical tracks like Hurricane Allen in 1980 and Bret in 1999, the ridge was much stronger than the one that is forecast. Plus those ridges didn't move like this one is going to. The models seem to keep this storm much weaker than it probably will be and as a much smaller storm. Is it going to turn as much as the models want, that much of a west turn from a ridge in the central plains? I don't think so, but I guess we will see.
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Quoting Daveg:
Sorry for the re-post, think my post got lost in all the talk earlier.

So, I would assume with the models bouncing north and south, and north and south. That anyone in northern Mexico and southern Texas should stay tuned, correct?

And is it due to the uncertainty in Alex's speed?

(noob here, trying to learn) :-)


Yes, that is correct.
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I'm begining to wonder if Alex is going to do anything...
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Sorry for the re-post, think my post got lost in all the talk earlier.

So, I would assume with the models bouncing north and south, and north and south. That anyone in northern Mexico and southern Texas should stay tuned, correct?

And is it due to the uncertainty in Alex's speed?

(noob here, trying to learn) :-)
Member Since: September 23, 2005 Posts: 0 Comments: 426

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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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