Alex continues to slowly organize
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
Reader Comments
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Northwest, I believe. I mean Alex will have little impact on the N. Gulf where I am. No oil please.
Hmmm, they didn't include the Cali/AZ border like GFDL does...I wonder whose right.
I see a pony!
No, but seriously, I see a very large system
AOI
AOI
AOI
Hurricane Hunter Data
TS BUSTED FORECAST ALIBI
i agree. to the one who wants stats with comments- this is an opinion blog. even the experts are just guessing and so far have been kinda wrong. not one met. or expert has said that this would stall out for so long. usually when a storm stalls its cuz its changing direction or relocating coc. Alex is not all the powerful yet. its just big. its still a tropical storm, not a hurricane. coc's have relocated before in tropical storms and hurricanes. nothing is impossible.
I didn't predict, I said "my gut feeling." My gut obviously does not have brains.
GOOD AGREEMENT IN BUILDING A RIDGE TO THE NORTH OF ALEX. THIS
SHOULD RESULT IN A TURN TOWARD THE NORTHWEST AND THEN TOWARD THE
WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS
I need to, just really busy ill start tomorrow.
New Orleans, Storm Relative Mean Radial Velocity
no that's COD. this is off topic. but it's funny. i'm a parttime bookkeeper for a small law firm and they use the acronym SDT for subpoena duces tecum. i write the checks to the COC (clerk of court) and i got in trouble because on a few of them I wrote "STD medical records of ...." rather than SDT
too early to say. 12Z models didn't have a great deal of data around Alex (which has been the case for several days except for some recon data) and so initialization hasn't been so good. Hopefully the G-IV data makes it into the 00Z assimilation cycles.
Obviously.
holy canoli Pat! Get the pirogue!
New Orleans, Velocity Azimuth Display Wind Profile Range 124 NMI
LOL!!
Least it aint 110F
Don't let your guard down yet. There are storms that do things like this:
Hurricane Elena.
Thanks StormW.....
Yeah, these are strange days, hydrus. LOL Having a hard time figuring what Alex is going to do. With all these numbers and charts it can get very confusing. Most of the stuff posted is way over my head.
Interesting...
exactly, you gotta realize school is out for summer and we are dealing with amateurs..
Those you list occur from their usual weather patterns and ocean currents. 3 days of wind with directions from perpendicular to away from the coast can, and does, generate upwelling just about anywhere. The S. Texas coast, for example, has upwelling during the mid to late summer every year, with south winds being responsible.
It happens everywhere from time to time, just not on the scales, in time or space, as those others you list.
Better get used to saying it again and again this season because it's one of those statements that never seems to sink in...
Hey, can we get a radar station in Cozumel? Not only would it give us a more advanced look at GOM cyclogenisis across the Yucatan and over to Cuba BUT I would be happy to work there, even in the summer!
Nope.
Not expanding here....
Thank you kindly.
You need to stop, few can understand thet....
No use, he never learned to paddle.
Cancun has a functioning radar...range just doesn't reach Alex.
Hence why I said this and all other blogs are opinions. I'm not sure why some type "IMO" or "IMHO". Obviously all are opinions. However, thanks for affirming!
I've experienced plenty of upwelling in the GOM first hand, especially in 2004 and 2005.
LOL!
And I did say a couple of days back that we don't really know how Alex would handle the lesser OHC on this side of the Yucatan.
Structure remains excellent. We just need uniformed convection and Alex will be on its way when Alex taps into that deeper TCHP and SST's to its north.
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