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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1007. Levi32
Guys.....what....1 hour of perhaps 6mph northerly movement is not a significant deviation from the NHC track. Give it time....if the long-term motion is well north of the NHC track then it will be significant. Rapid-scan imagery is addicting with images every 10 minutes but storms in weak steering currents wobble all over the place. Have patience before saying "Houston we have a problem".
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1006. xcool
that bad news
Member Since: September 26, 2009 Posts: 2 Comments: 15684

Quoting Jeff9641:
moving ne right now.
Looks like it is an allusion because of convection building on the eastern side giving the impression of NE motion, but to me Alex just seems to be spinning around in place.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1004. KEEPEROFTHEGATE (Mod)
Quoting oddspeed:
Look at that face:
the many faces of alex
Quoting atmoaggie:
Cat 5 coming. Gonna go up to Houston, swing to Lake Charles, back out in to the gulf and re-intensify in 30 minutes, plaster NOLA, Bay St Louis through to Mobile, back out into the gulf, beeline to Tampa, cross the state via Orlando, Gainesville, JAX, then into gulf stream, hook right and go straight south, curve out at the last moment, make a sweeping curve and approach Miami like a jet coming in for landing at MIA.
Cat 5 the whole time, at that.
i guess its time to evac 40 million hmm
Member Since: July 15, 2006 Posts: 178 Comments: 56141
The weakness is there but w/o much steering current it is not going to react very quickly especially with its size so not sure what to make of it. Maybe that it will meander North and stay over the ocean longer then is forecast.
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lol There is a definate comedian here!
Member Since: September 1, 2008 Posts: 0 Comments: 672
I leave for a few hours and now we are going north again..... How far north are we figuring here???
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Storm is Alex moving NNE now?And should the northern Gulf watch this sudden turn?Remember this morning I ask you if you thought it would turn.And you said it wasnt in the analysis to do so.Boy I am getting a lil nerved right now.
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For the people in the path of this storm let's hope and pray there is no rapid intensification here.
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Quoting Jeff9641:
moving ne right now.
I only see north movement with the occasional eastward jog
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Quoting StormW:


Take a look closely at that ridge.


Hmm? It looks well pushed to the east. The only steering currents with the ridge that would move a storm due W generally end at the Leeward islands. So there's a gigantic weakness. Other than that I'm not sure what I'm supposed to notice. Enlighten me :)
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996. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting skepticall2:


I had to ask off the blog so I didn't look like a noob but this graph sums it up perfect!
Don't worry about it, ask all the questions you want.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Patrap:




Thats not a weakness..

Thats da Muther of all weakness lad..

*cue music*
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Quoting StormW:


Where you see the space between TX and LA...That's where he will try to go, temporarily


was this weakness forecasted? i mean, would the NHC have known it was going to be there and taken that into account on their forecasted landfall?
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961. HurricaneSwirl 10:53 PM GMT on June 28, 2010
Quoting HurricaneSwirl:


Because it's temporary.


Which is why a lot of models have it going north and then a curve West. That is the ridge setting back in.


Have you seen your ridge coming....its way up in the mountains out west.....don't expect much of a ridge to build very quickly.

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Quoting TampaSpin:
There is gonna be a lot of wrong peps that had this going into Mexico! NO WAY its going anywhere inland close to Mexico.
Unless that ridge builds back in, Mexico shouldn't worry.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
...so Alex will be visiting Texas?
Member Since: September 1, 2008 Posts: 0 Comments: 672
I had to step away for a little while, what did I miss?
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Quoting StormW:


Where you see the space between TX and LA...That's where he will try to go, temporarily



Oh, I thought it was not good as in the new low expected to develop in the NE Gulf by July 3rd

http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2010062812-alex01l&field=Sea+Level+Pressure&hour=An imation
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Quoting stormpetrol:
I actually think the center of Alex is drifting slightly a little east of due north.


So do I
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Quoting StormW:


If he speeds up and that weakness stays for a while, he won't


Got it and thanks to the others that responded as well.
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Quoting HurricaneSwirl:


Which is why a lot of models have it going north and then a curve West. That is the ridge setting back in.


actually go back 3 and 6 hours on that steering map, the ridge isn't setting back in, the trof pushed it away
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979. xcool
. TampaSpin YOU SO RIGTH..
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting leo305:


So it moved NE, and is moving NNE/NE
No. Just some wobbles, no real proof that it is actual movement.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
Some people were asking what the steering map showed so I just went ahead and made a graphic.





Uh-Oh, the side of your arrow slightly touched NOLA!! You will be forever be labeled a NOLAcaster, doomcaster, wishcaster, and now the all-new term "weakness-caster".
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Quoting kmanislander:
Alex is about to put on a show in intensification. Deep convection blowing up everywhere now it seems. I would not be surprised to see this make hurricane status well before the forecast point for that to happen.

The weakness in the steering has now extended East over LA which would encourage a path due N from where it is now. If that ridge does not build back quickly the track forecast may have to be adjusted Northward once again particularly if Alex drops a few mbs tonight.
Quoting kmanislander:
Alex is about to put on a show in intensification. Deep convection blowing up everywhere now it seems. I would not be surprised to see this make hurricane status well before the forecast point for that to happen.

The weakness in the steering has now extended East over LA which would encourage a path due N from where it is now. If that ridge does not build back quickly the track forecast may have to be adjusted Northward once again particularly if Alex drops a few mbs tonight.



Hey, Kman. Thanks. And, I'm thinking Alex has been helping to create its own weakness to the north. We've been getting pummeled nearly all day here with outflow from the system. If it starts intensifying, gets a natural 1 or 2 degree coriolis tug and starts feeling that weakness, it becomes a game changer imo.


Question, too, for the MODEL EXPERTS - are you certain they're built, smart enough to ingest a system of this size? Incredible.
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Quoting TampaSpin:
There is gonna be a lot of wrong peps that had this going into Mexico! NO WAY its going anywhere inland close to Mexico.




nop
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Quoting StormW:


Correct.


Like strait north to Louisiana?
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there is another trof coming down behind this one
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Quoting MiamiHurricanes09:
Some people were asking what the steering map showed so I just went ahead and made a graphic.




oh now just cut that out!!!! please?
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Looks like BP is reacting to Alex.

http://news.yahoo.com/s/nm/20100628/ts_nm/us_oil_spill_cap
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oh 03 has open his commets up in his blog

Link
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Thats not a weakness..

Thats da Muther of all weakness lad..
Member Since: July 3, 2005 Posts: 428 Comments: 129902
There is gonna be a lot of wrong peps that had this going into Mexico! NO WAY its going anywhere inland close to Mexico.
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Link to Texas Emergency Preparedness info.
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Some people were asking what the steering map showed so I just went ahead and made a graphic.



Member Since: September 2, 2009 Posts: 130 Comments: 21194
I actually think the center of Alex is drifting slightly a little east of due north.
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Quoting HurricaneSwirl:


Because it's temporary.


Which is why a lot of models have it going north and then a curve West. That is the ridge setting back in.
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TropicalStormAlex heads toward beach landing to free(Port)Lavaca(Texas) in 10days6hours
(Straightline projection using its last 2 positions. Take with HUGE grain of salt)

Copy&paste TAM, MOB, PBI, SAL, 19.4N91.3W, 19.7N91.6W-28.7N88.4W, 20.3N91.7W-28.7N88.4W, 20.5N91.8W-28.7N88.4W, 20.3N91.7W-20.5N91.8W, 20.5N91.8W-28.5N096.1W into the GreatCircleMapper.

The shortest red line shows the heading between the last two positions. Below the map shows:
TSAlex had a heading of 338.4degrees (~1degrees north of NorthNorthWest), while
traveling a distance of 15miles (~24kilometres) over 6hours at a speed of 2.5mph (~4kph);
TSAlex's distance from DeepwaterHorizon* decreased by 11miles from 614miles to 603miles;
the previous closure rate was ~6mph, and at the current closure rate of ~2mph,
TSAlex remains ~334hours away from the DeepwaterHorizon.

At 120hours away, personnel evacuations & shutdown procedures for ship evacuations begin.
(See the bottom of blog1521post705 for more info, & blog1521post3353 before obvious corrections)

* Which I've been marking as 28.7N88.4W
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CC texas is looking to be the sweet spot for Alex to slam ashore. Cat 2-3 bringing heavy rains to a presoaked texas...flash flood galore is what we will see...
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Data from NOAA Buoy 42005, about 120 NMi WNW of Alex CoC.

current p tendency -2.3 mb/h
Link
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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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