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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2157. GetReal
My latest thoughts on Alex...
Member Since: Posts: Comments:
2156. xcool
MrstormX :0
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Scary stuff...980mb..in June - and more time left for it to intensify.
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Quoting MrstormX:
Huge!





See the image from the movie the day after tomorrow. Starting to look that HUGE. Welcome to climate change.
Member Since: Posts: Comments:
Quoting Snowlover123:
00Z NAM has problems with Alex- splits it into 2 lows.



Forget the NAM... throw it out
Member Since: Posts: Comments:
Quoting GlobalWarming:


xcool, i was being all nice and conversational with you, why are you treating me this way? :(.


Hey GW. How are things in SFL?
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Quoting MiamiHurricanes09:
New minimum central pressure is 985.3mb.

000
URNT15 KNHC 290214
AF304 0701A ALEX HDOB 34 20100629
020500 2052N 09133W 9252 00554 9854 +223 +209 154002 006 019 002 03
020530 2052N 09133W 9252 00554 9853 +229 +211 334004 006 018 003 00
020600 2050N 09136W 9253 00555 9856 +230 +214 312008 008 017 001 00
020630 2049N 09137W 9245 00565 9859 +225 +216 296013 019 017 000 00
020700 2047N 09138W 9250 00564 9860 +240 +218 302030 037 027 003 00
020730 2046N 09139W 9243 00578 9869 +235 +220 307039 040 032 003 00
020800 2045N 09140W 9246 00582 9878 +235 +222 302040 041 035 002 00
020830 2044N 09141W 9253 00584 9890 +221 +221 302037 038 034 002 00
020900 2042N 09142W 9253 00592 9897 +226 +224 301037 037 034 002 00
020930 2041N 09143W 9248 00604 9906 +219 +219 309035 037 034 001 00
021000 2040N 09144W 9249 00608 9915 +212 +212 318036 038 033 002 00
021030 2038N 09145W 9249 00612 9922 +210 +210 317036 037 032 002 03
021100 2037N 09146W 9246 00621 9927 +209 +209 317035 036 031 002 03
021130 2037N 09147W 9250 00620 9931 +209 +209 318034 035 032 003 00
021200 2036N 09149W 9249 00625 9935 +210 +210 319032 033 031 003 00
021230 2035N 09150W 9247 00629 9938 +210 +210 320032 034 031 002 00
021300 2034N 09151W 9250 00630 9941 +210 +210 320030 031 030 001 00
021330 2033N 09153W 9248 00635 9944 +208 +208 322030 031 029 002 00
021400 2032N 09154W 9252 00633 9948 +206 +206 325030 031 028 002 00
021430 2031N 09155W 9249 00639 9951 +209 +205 323030 031 030 001 00
$$
;

whats is the lowest pressure for a ts anyone
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2148. scott39
How far out will tropical force winds be felt from center?
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2147. xcool
. GlobalWarming i'm nice all day ;)
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting Chigz:

HAHA!! Are you now replying to your own comments!
Models are shifting back and forth - nothing is set in stone yet!
Don't see this going to TX/MX border....more north!


Uhh.that was an accident. And I am calling for a Brownsville hit. And I am sticking with my guns.
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980MB is a Hurricane for sure,

The Storm is very ugly and big, never see before a Storm like that in the month of June.
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2144. amd
Quoting CybrTeddy:
If we see a sub 980 mb TS that would be astounding.


that could happen in this case. I think there may be a double wind maxima thing going on here.

Just noticed that due east of the storm, the strongest flight winds (64 knots) were at 997.2 mb, while the strongest flight winds in the ne quandant was much closer to the center at 991.6 mb (67 knots).

Alex may be figuring out if it wants a very tight core, or a more diffuse core. IMO.
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Quoting scott39:
Is there anything to stop the pressure from dropping before land


Anything that weakens a tropical cyclone will cause the pressure to stop falling and in some instances to rise. These include shear, cold SST, dry air ingestion, proximity to land etc.
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00Z NAM has problems with Alex- splits it into 2 lows.

Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Yes and then slamming me and telling me that rapid intensification is occurring, pretty funny if you ask me.

Now. Enough of the drama and back to the tropics.


I CERTAINLY DID NOT SLAM YOU MIAMI. REALLY?

well atleast now everyone knows your 13 and you
can be forgiven for being less than expert.

how was i supposed to know? you were trying to errantly correct me
when i have been forecasting and researching storms for 25+ years.

trust me, im right about the intensification. im not here to make trouble.

RI is a process. and you are seeing it in ALEX or atleast very
close to RI.

even The best forecaster i know agree's Accuweather's Joe Bastardi
just mentioned it as well.
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2139. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15684
New minimum central pressure is 985.3mb.

000
URNT15 KNHC 290214
AF304 0701A ALEX HDOB 34 20100629
020500 2052N 09133W 9252 00554 9854 +223 +209 154002 006 019 002 03
020530 2052N 09133W 9252 00554 9853 +229 +211 334004 006 018 003 00
020600 2050N 09136W 9253 00555 9856 +230 +214 312008 008 017 001 00
020630 2049N 09137W 9245 00565 9859 +225 +216 296013 019 017 000 00
020700 2047N 09138W 9250 00564 9860 +240 +218 302030 037 027 003 00
020730 2046N 09139W 9243 00578 9869 +235 +220 307039 040 032 003 00
020800 2045N 09140W 9246 00582 9878 +235 +222 302040 041 035 002 00
020830 2044N 09141W 9253 00584 9890 +221 +221 302037 038 034 002 00
020900 2042N 09142W 9253 00592 9897 +226 +224 301037 037 034 002 00
020930 2041N 09143W 9248 00604 9906 +219 +219 309035 037 034 001 00
021000 2040N 09144W 9249 00608 9915 +212 +212 318036 038 033 002 00
021030 2038N 09145W 9249 00612 9922 +210 +210 317036 037 032 002 03
021100 2037N 09146W 9246 00621 9927 +209 +209 317035 036 031 002 03
021130 2037N 09147W 9250 00620 9931 +209 +209 318034 035 032 003 00
021200 2036N 09149W 9249 00625 9935 +210 +210 319032 033 031 003 00
021230 2035N 09150W 9247 00629 9938 +210 +210 320032 034 031 002 00
021300 2034N 09151W 9250 00630 9941 +210 +210 320030 031 030 001 00
021330 2033N 09153W 9248 00635 9944 +208 +208 322030 031 029 002 00
021400 2032N 09154W 9252 00633 9948 +206 +206 325030 031 028 002 00
021430 2031N 09155W 9249 00639 9951 +209 +205 323030 031 030 001 00
$$
;
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2136. Patrap
Latest RECON HH Tail # 304 Message
Member Since: July 3, 2005 Posts: 426 Comments: 129093
I have a question.....not very weather related......but why do people take this blog thingy so seriously?....take me back to my childhood please....when people had "real" relationships.....and arguments with people that they could actually see....
Member Since: September 1, 2008 Posts: 0 Comments: 672
Quoting RitaEvac:
going to be like Ike the winds may never catch up to the pressure, its so damn big,
Ike's winds did catch up to the pressure. It was just such a large system, it had lower winds than usual due to its angular momentum.
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2133. scott39
Quoting Max1023:
2101 - Roughly 990mb for a small 75mph system to 970mb for a large 90mph system.

Alex is so large that it will likely hit 75mph with a pressure around 975mb, it might need sub-960 to make it to Cat 2.
Thanks
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2132. Cranica
There are two reasons Alex's winds are lagging behind his pressure. First, he's strengthening, and winds take time to catch up to pressure. Second, background (i.e., outside the storm) pressures are very low, and it's the difference in pressure that produces winds.
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2131. USSINS
Quoting Patrap:


Shucks Blood,..baby gon rip dat line and mabe due the single out Holmes




Fruition. Yup.
I told you Alex was winking at us as night fell. It literally blew up in the center right as night was falling. I'm no meteorologist but I know what I saw. I also know to trust the critters and mine have been acting crazy today. Even the wild ones have been silent and I'm all the way in Panama City. Alex is sucking in everything he can right now including what is left of Darby.
Member Since: June 27, 2010 Posts: 0 Comments: 760
2129. centex
There are still lots of unknowns or factors which have some uncertainty in timing and strength. 1) How fast will weakness go away? 2) How strong will ridge build in. 3) how strong will Alex get and how fast will she move.
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Quoting StormW:


Going good! Won't be on too much longer...back up at 5:00 a.m. How are you this evening?


Exhausted turning in early myself. Hey you gotta send me mail next time you'll be on the BB show. I wanna heaaaaaaar. And don't know if you know but I had posted a question regarding Alex on your blog not today's but yesterday's I believe.
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2127. amd
Quoting FLdewey:
In the news... Hurricane bound for texas slowed by large land mass to the South.


one of the best pieces of satire by the Onion ever.

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I think we did reach the minimum pressure. Let's see what the next HDOB message shows...
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2124. scott39
Quoting StormW:


Thanks Pat...see yas as well!
Is there anything to stop the pressure from dropping before land
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2123. Max1023
2101 - Roughly 990mb for a small 75mph system to 970mb for a large 90mph system.

Alex is so large that it will likely hit 75mph with a pressure around 975mb, it might need sub-960 to make it to Cat 2.
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going to be like Ike the winds may never catch up to the pressure, its so damn big,
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2121. xcool
GlobalWarming i'm not anyway bye backtropical weather,
Member Since: September 26, 2009 Posts: 2 Comments: 15684
Quoting tkeith:
Billy Nunnguesser will put him on a backhoe if stays there long Pat...


Billy knows how to get things done!
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Yea storm great job tonight! Really cleared things up for me.
Member Since: July 8, 2005 Posts: 259 Comments: 24508
2117. Chigz
Quoting tennisgirl08:

HAHA!! Are you now replying to your own comments!
Models are shifting back and forth - nothing is set in stone yet!
Don't see this going to TX/MX border....more north!
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Quoting scott39:
What are the pressures of a Cat 1


although now NHC only uses wind to determine the strength of the system.... normally a cat 1 hurricane is from 980-990 pressure sometimes lower sometimes higher
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Okay guys, so early 00Z models are shifting north, and I'm about to hit the sack. Night all.
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2113. Patrap
Quoting tkeith:
Billy Nunnguesser will put him on a backhoe if stays there long Pat...


Dats how Billy roll's fo sho tkeith.

Member Since: July 3, 2005 Posts: 426 Comments: 129093
I say Brownsville is going to get a bad storm. BTW - I think we need to quit arguing over intensity and track and focus on the fact that we are discussing Aug/Sept type hurricanes in JUNE! Long season ahead..
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2111. tkeith
breath in, and breath out.

move on~Buffet...
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Quoting skkippboo:


Oh give me a break, the levees are fine. This is just a political scare tactic to get the voters to approve bond issues in that county to raise the levees, like they did in neighboring Hidalgo County where I live.


Don't shoot the messenger lol
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Quoting MrstormX:


Could have a hurricane in time for the 11:00 news.


we are getting close to what would be equivalent to a cat 2 hurricane pressure
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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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