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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No Wilma was a hurricane at the time but that was the lowest pressure recorded in a storm.
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2306. redux
I have been a long time lurker here-- about 5 years.

I really enjoy reading this informed commentary about tropical and other severe weather.


keep up the good work.
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Hypothesis: The size of the hurricane is an indirect determining factor on wind speed as related to pressure.

Basically, inertia: As Alex is a monstrously large storm, that massively deep pressure for its strength SEEMS massive, but translates to a weaker system in wind speed because of the energy required to spin the damn thing.
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2304. jpsb
Quoting angiest:


Times are given in GMT/Zulu time.
6 hours ahead of east coast time?
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Quoting tennisgirl08:


Its not even funny to joke about that. Really.

wasnt joking alex is one mean storm its a tradigy really i hate bp so much right now Tony didlydoright needs to be droped out of a hurricane hunter and into alex
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Be back in a sec...
Member Since: September 2, 2009 Posts: 130 Comments: 21194
2301. Drakoen
Much better organized:

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Houston's Fox Affiliate just reported a change in models that were converging on Corpus Christi. He also said the models would move again. Went to store for some groceries and all the water and beer are gone. I guess some people are paying attention.
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i need those 00Z runs of dynamicals, can someone post
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2298. brla61
Quoting CaneWarning:


If I were to listen to some on here tonight, I would be putting up my hurricane shutters...and I'm in Tampa! LOL

i feel u.i'm a first responder.so,i'm in alert mode most of the time. i filter out unneccessary info and move on. it's just the nature of the beast
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That might be the CDO starting to form? From there, with a few updrafts and another pressure drop Alex could receive an eye.
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2296. Patrap
ALEX RECON HH Tail # 304 Latest Message
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I think it's moving North due to friction with land. A notable example of this is Isidore (2002). It moves towards the land if steering currents are weak. It's like if you drift off the road in your car and there are stones on the side, you'll be dragged in.

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2294. 7544
Drakoen 10:32 PM EDT on June 28, 2010
Alex looking good at this hour with deep convection over the center. Latest recon coordinates suggest the system is moving somewhat to the NNE.
Action: Quote | Ignore User

thanks for clearing that up so record was and i was right hmmmmm
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Quoting Patrap:

from 2004

.."It cant be going to Punta Gorda,,the Map says Tampa"..


Oh boy, I remember that. lol I just kept praying to the 'cane gods please please not Tampa not Tampa...
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Quoting kmanislander:


Physics at work. No steering so the motion of th earth has taken over temporarily.
I heard you talking about it earlier and I found it very intriguing, thanks for sharing.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting HoustonTxGal:
Lowest recorded pressure in a hurricane goes to WILMA in 2005. Pressure of 882mb

what is it to a tropical storm
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Quoting CaneWarning:


Orca, should I immediately begin to prepare here in Tampa?


First... if you live in the GOM, you should be prepared already. Common sense for the season.

Second... I don't even pretend to be a forecaster, that is what the NHC is for. Their success rate within 3 days of landfall is vastly superior to the information you will get here.
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Quoting AlexEmmett:

the oil cow it wants the thick nasty brown milshake


Its not even funny to joke about that. Really.
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Lowest recorded pressure in a hurricane goes to WILMA in 2005. Pressure of 882mb
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Thanks miami!
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Quoting MiamiHurricanes09:
Basic northward motion with the slightest hint of eastward motion.



Physics at work. No steering so the motion of the earth has taken over temporarily.
Member Since: August 19, 2006 Posts: 0 Comments: 15948
Quoting TropicalNonsense:


wow...Baha our once very knowledgable and resourceful blog is
turning into Romper-Room!


People are getting frustrated with the kiddie stuff.

poof numero one of my ingore list which by the end of the year my be bigger than alex the cow
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2283. nash28
Keep in mind it is gonna take some time for the winds to catch up to the 985mb pressure reading. We're not talking Charley here. Charley was a tight yo-yo. This is a HUGE system folks. Keep it together.
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so only on and off the blog tonight... is the consensus still stx or have the uber-knowledgable folks gone with the nhc and moved to nmx?
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2281. tkeith
Quoting Drakoen:
Looks like just east of due north.
can you tell from those frames if the forward motion has picked up the pace?...still seems to be crawling to me...
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2258: Only because you're here, wasting electrons...
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Quoting Patrap:
ALEX RECON HH Tail # 304 Latest Message
Thank you for posting these..apparently only a few of us actually read them. They are very helpful!
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Quoting connie1976:
Is it me or does Alex look like it's moving now? (in a nnw direction?)


Steering analysis would certainly indicate such, at least near-term.
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2276. Patrap

from 2004

.."It cant be going to Punta Gorda,,the Map says Tampa"..
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Basic northward motion with the slightest hint of eastward motion. I would say Alex is moving slowly towards the NNE.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
2274. ssmate
Quoting MrstormX:


Think Dolly but Double Sized, ick
I always think of Dolly as double sized.
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F5 time
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Quoting PanhandleChuck:
Wow, this is the roughest crowd I've seen all season. Only been on here for three years, but I know when to lay low.


kids.
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2271. amd
someone asked a question about the lowest pressure found on a tropical storm (I'm going to add while still on water and not becoming extra-tropical) and I found this:

Both Opal and Wilma had 70 mph winds with pressure of 980 mb.

Opal Report/a>

Wilma last public advisory before becoming a hurricane

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Quoting GlobalWarming:


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


JFV GET A LIFE!
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ok - back. So, anything interesting from recon?
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Talk about a monster storm, on my favorite nigh-time ir image he appears he could engulf all the BOC and more.

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Quoting Patrap:
.."da wheel in da gulf goes round and round"..

yah pat lol the big but wheel
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2266. Drakoen
Looks like just east of due north.
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2265. jsit
I dont know where the thing is going - I kind of find it wierd to guess when 'to me' there doesnt seem to be an eye yet. (dunno how Noaa does it - but its cool with me- they know better than I do)

however Lol- in Corpus' Annaville Walmart they are just about out of water and there are absolutely no D cell batteries in the place.
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Quoting BahaHurican:
I rarely go out of my way to insult pple in here, but something about the way you are posting is making want to really blow u out of the water. Be that as it may.....

I'm curious which cat two storms you have seen which looked worse than Alex does now. We'd LOVE to see some imagery if you can find it..... on your other points, you made two non sequiturs in response to the post u quoted. First, you said something about nature not paying attention to textbook definitions, when the poster was actually speaking about OTHER BLOGGERS paying attention to the correct usage of terminology (what's Mother Nature got to do with what he said?). Second, you said something to the effect of "RI soon to come" when the blogger was actually saying no RI happening right now.

I'm getting rather weary of your constantly bombastically bombarding statements about Alex moving NE and hitting Florida based on a brief bobble and your "gut feeling". Give me some meteorological proof, and stop trying to ram your gut feeling down MY throat.

YMMV.


wow...Baha our once very knowledgable and resourceful blog is
turning into Romper-Room!


People are getting frustrated with the kiddie stuff.
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Quoting MiamiHurricanes09:
LOL! Alex the cow.

the oil cow it wants the thick nasty brown milshake
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Quoting ElConando:


Moocaster!


That's udderly ridiculous
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2261. Drakoen
Alex looking good at this hour with deep convection over the center. Latest recon coordinates suggest the system is moving somewhat to the NNE.
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Quoting Patrap:


Dat should rattle the masses.


Well its gonna say N on the advisory per NHC but the people on here will prob take it and run.
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Storm W.. How north will Alex go if the High pressure is not strong enough? From the 4pm advisory to 7pm... Alex it moved .1 N and .2 East
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Quoting jaevortex:


That is one huge system and it's scaring me.

Scares me that we still burning oil.
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Quoting stillwaiting:
alex looks like he's turning into a monster!!!!!(large)...


Think Dolly but Double Sized, ick
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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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