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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I vaguely recall that there is SUPPOSED to be a northerly component to Alex's movement for the first 24 - 48 off the Yucatan. I must admit though, that the westerly which was supposed to take it off the continental shelf seems rather.... lacking.... I'm still sticking to my notion of a Laguna Madre landfall.... but I'm now thinking a bit closer to the Corpus end than the La Pesca end..... will be interesting to see how far north this gets before a more westerly movement sets in.
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Quoting Orcasystems:
HH inbound, this should settle some questions.


You would think, but in here?... ;)
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Quoting MZV:
Please stop with the moving east hooey. You are staring at the images too long and seeing things. Next you'll be telling us Elvis or the Virgin Mary is in there!
LMAO!!! Time will tell one way or the other!
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Oh man am I getting a laugh! Only at WU.
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Quoting xcool:


new update


the ridge is building a little bit stronger and further south now. i think the NHC track will verify. Alex will stall and then proceed WNW..NW motion towards TX/MX border.

You "eastcasters" need to give it up..LOL!
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noaa recon on the way down to alex also.
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Quoting MZV:
Please stop with the moving east hooey. You are staring at the images too long and seeing things. Next you'll be telling us Elvis or the Virgin Mary is in there!
Nah... but I did think I saw Jimmy Hoffa!
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Quoting jaevortex:


Roger, over.


uh?
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Looks like Alex is starting to wind up now
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Quoting kmanislander:
Scott 39

Here is the conversion chart for mbs to feet above sea level for steering.

mbs to feet above sea level
Very important graph for sure.

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1946. MZV
Quoting DestinJeff:


or to quit sniffing glue.


Is this revealing our ages? LOL Shirley some of the young twerps here are getting it
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1944. nash28
Ok Jeff. I aplogize for the use of that word. You're right. I was once that blogger.

My fault. But let's keep it real.
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cones of uncertainty
RITA Graphics Archive
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MVZ, That was funny lol. I agree the sat images will start making you see things, It kinda like playing Black Jack all night at the casino. When you close your eyes at night, thats all you see is A's & K's lol.
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Yikes model madness

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Quoting DestinJeff:


or to quit sniffing glue.


I don't think they quit :(
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Scott 39

Here is the conversion chart for mbs to feet above sea level for steering.

mbs to feet above sea level
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1938. KORBIN
StormW- Thank you for answering all our our questions! You are a man of great knowledge.
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Progster and Atmo: both very good examples of 2D models of why the quarterback has to lead the receiver of the pass. The earth is a sphere, therefor 3D.

Lacking steering influence can anyone tell me why Alex won't go north?
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excuse me..stewardess...I speak jive!

"Blood can't hang say north east goes seven up."
Member Since: August 16, 2007 Posts: 1 Comments: 2351
1935. scott39
Quoting kmanislander:


The general rule is that the deeper the system ( that is the lower the barometric pressure )the higher up in the atmosphere the steering winds are located.

This diagram shows the pressure of the system on the bottom and the height above sea level in mbs for the steering winds on the left. I will post a graph converting mbs to feet above sea level in a moment.
Thanks
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Quoting tennisgirl08:
Latest images show Alex getting squashed on its western side, maybe entraining some dry air - this might give the appearance of a NE motion.


It used to not have any convection at all on the W side, not squashed, it's just that it's new W convection isn't complete yet.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
1933. Chigz
Quoting TexasHurricane:


Hi xcool - what is your thoughts on Alex this evening?

For GFDL model to verify, Alex needs to WNW right NOW! Since that's not going to happen I think we can throw away 12Z and 18Z GFDL out!

18Z GFS is not south of Corpus, right on top of 18Z HWRF! 00Z BAM suite have moved close to Corpus

In short, nothing is set in stone!
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I dont know why the NHC went a tad south, should of stayed where they were at 1PM. Now if they need to shift north again it's going to be even a bigger jump north
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Wow ... The Spiral banding and Circulation extend far into the Pacific.

Behold a Major Storm in the making!!! ....



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1930. angiest
Quoting galvestonhurricane:
Is there any chance Alex could make a landfall closer to Matagorda Bay?


Possible? Of course. Unfortunately, too early to say given that the environmental data haven't been incorporated into the models yet. And, unfortunately, the final picture may not come together soon enough.

If you live in coastal Texas, keep watching. A landfall in Matagorda would be pretty bad for the western half of the Houston area, including West Galveston. Assuming the windfield is as large as forecast, of course.
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Quoting nash28:
That's Clarence Oever, over...


Roger, over.
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HH inbound, this should settle some questions.
My guesstimate... webbles and wobble, but basically stationary.
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Good evening once again!

00Z Spaghetti Models



One model consensus seems to be traveling to the TX/MX border, and another model consensus takes it to Texas.

-Snowlover123
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting TropicalNonsense:
Alex is going thru a Rapid Intensification Cycle at this very moment.

When the convection finishes building around the eye...look out!
#1. Alex is not developing an eye first because it needs a well-established CDO before any of that happens.

#2. Alex is not rapidly intensifying because this is the NHC term of rapidly intensifying:

A decrease in the minimum sea-level pressure of a tropical cyclone of 1.75 mb/hr or 42 mb for 24 hours.
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1923. Detrina
Quoting MZV:
Please stop with the moving east hooey. You are staring at the images too long and seeing things. Next you'll be telling us Elvis or the Virgin Mary is in there!


Elvis was at the Dunkin Donuts just this morning, gettin a jelly donut! Bwahwahwah:)
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Well, I cant say anything more than "I told you so."

Storm, Atmo, Kman if you're around, what do you think on the Trough? I said yesterday I though it was pushing much harder than the forecast had shown, and unless the vortex fix was a reformation, we've got some element of eastward movement. (It's tiny, but apparent.) So, what next?
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I think that the center of the storm is located around 92.1W and 20.6 N



Link

The last two frames show a wobble to the west, might be starting to follow the forecasted WNW track.
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Quoting stormwatcher247:
Does it appear that Alex is drifting north?

It is ever so slightly east of due north
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1919. 7544
hmm more pepps are seeing the ne motion now
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1917. Ossqss
How does the other trough coming from the west impact the scenario in a few days? Will it play a role?
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1916. xcool
. ElConandolol
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting scott39:
Hey Kman, Can you give a summary on how TCs are steered?


The general rule is that the deeper the system ( that is the lower the barometric pressure )the higher up in the atmosphere the steering winds are located.

This diagram shows the pressure of the system on the bottom and the height above sea level in mbs for the steering winds on the left. I will post a graph converting mbs to feet above sea level in a moment.
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1912. xcool


new update
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Latest images show Alex getting squashed on its western side, maybe entraining some dry air - this might give the appearance of a NE motion.
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Quoting galvestonhurricane:
Is there any chance Alex could make a landfall closer to Matagorda Bay?
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Does it appear that Alex is drifting north?
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Hurricane Alex 2pm or 8am.
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1907. nash28
That's Clarence Oever, over...
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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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