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 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.

Have you been reading my blog?
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-80C cloudtops directly over the COC.
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Quoting gator23:

I also doubt "he" will explode. they downgraded their forecast.
Disagree with that one. All he needs to do is move a couple degrees north in latitude before reaching waters with more TCHP. Plus shear shouldn't be a problem. I could easily see Alex becoming a category 2 hurricane, now category 3 status is a bit of a stretch unless he stalls further north where the warmer TCHP are.
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that storm is moving east there is no doubt about it the track will change i have been saying this is a miss/al storm
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852. xcool


OH WOW
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Quoting alexhurricane1991:
Intensity forecasts are very low confidence forecasts cant take them word for word.

WU forecasts are even lower confidence I never take them letter for letter.
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Quoting jasoniscoolman09:


He looks good compared to this morning. He'll look even better if he fills in his west side and the northern half of his COC.
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Quoting jasoniscoolman09:
okay this is getting crazy... there are totally two distinct separate centers now!
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2115 UTC Dvorak Image ALEX

Member Since: July 3, 2005 Posts: 424 Comments: 128259
Quoting hurricanehanna:
okay, I drove home as quick as I could to log back on to this site....so what happened in the past 30 minutes????
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.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Quoting will45:


He out there on a crop duster taking measurements


LMAO!!! And I bet your right lol.
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Quoting GeoffreyWPB:


Look at that ULL by the Bahamas moving west. Imagine what the blog would be like if that was an organized system!


if Alex goes MAJOR HURRICANE on us, the ULL may pull it more to the east
Member Since: April 17, 2010 Posts: 0 Comments: 1753
An earlier poster whs2012 said they heard Fox 26 here in Houston state that Galveston had a 40% chance of getting hit by Alex.
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Is it going due north?
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Quoting Hurricanes101:


yea cuz tropical systems wait for the NHC to give the go ahead before they intensify lol

generally speaking, this has been my experience yes.
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I'm not sure the High Pressure that will come in following the trough is gonna be a big player....seems very high over the ConUS in the Mountains now......with another trough looks like trying to come in very fast on the back side and digging.....this is gonna be very interestng couple of days.
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Quoting gator23:

I also doubt "he" will explode. they downgraded their forecast.
Intensity forecasts are very low confidence forecasts cant take them word for word.
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.
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Quoting weatherwonderer:
Damn wish StormTop was here we need his expertise. He would have had the track and intensity all plotted out. All we would have to do is watch. HeHe

Actually miss his presence myself. BTW hi guys lol


He out there on a crop duster taking measurements
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Quoting gator23:

I also doubt "he" will explode. they downgraded their forecast.


yea cuz tropical systems wait for the NHC to give the go ahead before they intensify lol
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Quoting HoustonTxGal:


What news agency is stating that?


Saw that too, pretty sure the met's name was Strom Topper or something like that...
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Large burst of convection over Alex's center, should get going properly soon. Recon inbound so we'll be able to watch as it happens.
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01L/TS/A/CX
MARK
21.1N/91.5W

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Is it an optical illusion, or is Alex going due North.
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Quoting MiamiHurricanes09:
I doubt shear will be a problem in a couple days. One thing hindering development at the moment is the cold TCHP below.

I also doubt "he" will explode. they downgraded their forecast.
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I usually watch Fox 26 here in Houston but I don't have it on right now.. will have to watch it at 10pm to see what they say then.
Member Since: September 18, 2007 Posts: 0 Comments: 1074
Damn wish StormTop was here we need his expertise. He would have had the track and intensity all plotted out. All we would have to do is watch. HeHe

Actually miss his presence myself. BTW hi guys lol
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Quoting TampaSpin:


Yep, once it gets moving some....he will likely explode very quickly and then balance out because of the 10-15kt of shear.
I doubt shear will be a problem in a couple days. One thing that will likely be hindering development is the cold TCHP below.
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823. xcool
ElConando LMAO.
Member Since: September 26, 2009 Posts: 2 Comments: 15670
Storm Surge Scales and Storm Surge Forecasting

During the open public comment period for the draft of the Saffir-Simpson Hurricane Wind Scale, many people suggested that the National Weather Service develop a storm surge specific scale as well as improve its forecasting of storm surge. It is acknowledged that there are some researchers who advocate developing another scale for hurricanes specifically geared toward storm surge impact1,2 by incorporating aspects of the system's size. However, the National Hurricane Center does not believe that such scales would be helpful or effective at conveying the storm surge threat. For example, if 2008's Hurricane Ike had made landfall in Palm Beach, Florida, the resulting storm surge would have been only 8', rather than the 20' that occurred where Ike actually made landfall on the upper Texas coast. These greatly differing surge impacts arise from differences in the local bathymetry (the shallow Gulf waters off of Texas enhance storm surge while the deep ocean depths off of southeastern Florida inhibit surge). The proposed storm surge scales that consider storm size do not consider these local factors that play a crucial role in determining actual surge impacts.

The National Weather Service believes that a better approach is to focus directly on conveying the depth of inundation expected at the coast and inland. Because storm surge-induced flooding has killed more people in the United States in hurricanes than all other hurricane-related threats (freshwater flooding, winds, and tornadoes) combined since 19003 the National Oceanic and Atmospheric Administration is working to enhance the analysis and prediction of storm surge. Direct estimates of inundation are being communicated in the NHC's Public Advisories and in the Weather Forecast Office's Hurricane Local Statements. New ways of communicating the threat have also been developed. NHC's probabilistic storm surge product, which provides the likelihood of storm surge values from 2 through 25 feet, became operational in 2009, and the NWS's Meteorological Development Laboratory is providing experimental, probabilistic storm surge exceedance products for 2010. In addition, coastal WFOs will provide experimental Tropical Cyclone Impacts Graphics in 2010; these include a qualitative graphic on the expected storm surge impacts. Finally, the NWS is exploring the possibility of issuing explicit Storm Surge Warnings, and such warnings could be implemented in the next couple of years. In all of these efforts, the NWS is working to provide specific and quantitative information to support decision-making at the local level.
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Quoting MiamiHurricanes09:
Don't see any eastward component in motion as convection has begun to fire in and around the center. Looks like N/NNW motion with some slight wobbles but overall slow motion.
Any eastward component will be from wobbles but i agree no easterly movement just north/nnw right now
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Quoting TampaSpin:


Ya, i hear ya....looks like a wobble here and a wobble there....to only travel not even 70 miles in the last 12hrs....pretty hard to draw a line of direction.


Look at that ULL by the Bahamas moving west. Imagine what the blog would be like if that was an organized system!
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Quoting gator23:

JFV showed up, Rodney Dangerfield showed up and then you got here. So... nothing

whew....time to grab a brewsky then...thanks! Thunderboomers popping overhead from Alex's long arm
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NHC Storm Surge Scales and Storm Surge Forecasting
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Quoting RecordSeason:
776:

You are correct.

The storm's center is moving NNE to NE for several frames, as I anticipated.

http://weather.msfc.nasa.gov/cgi-bin/post-goes


You cant even see the center too much coverage.
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Quoting ElConando:
Someone tell JFV what the Edeye model shows.

It shows Alex going to tropics chat.
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Quoting whs2012:


It was on the fox 26 chat thingy.


I finally had to turn Fox26 off here in Houston when they just brought on this young lady to discuss how to talk to your children about hurricanes. The only good thing about Fox26 is Sibila Vargas ;)
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Quoting TampaSpin:


Yep, once it gets moving some....he will likely explode very quickly and then balance out because of the 10-15kt of shear.


Shear will be gone in 24 hours.
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Quoting Levi32:


Might be moving a couple mph faster to the north during the last hour. He's definitely got some nice banding going on. As soon as he gets out of the cold upwelled shelf waters he will take off fast.


Yep, once it gets moving some....he will likely explode very quickly and then balance out because of the 10-15kt of shear.
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Quoting Floodman:


"I tell ya, I get no respect...I met the surgeon general - he offered me a cigarette."

LOL...


love it!!!
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We are all Blog Addicted.
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Someone tell JFV what the Edeye model shows.
Member Since: September 6, 2009 Posts: 2 Comments: 3719
Quoting RecordSeason:
776:

You are correct.

The storm's center is moving NNE to NE for several frames, as I anticipated.

http://weather.msfc.nasa.gov/cgi-bin/post-goes
I don't see any eastward component in motion as convection has begun to fire in and around the center. Looks like N/NNW motion with some slight wobbles with overall slow motion.
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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.