Alex continues to slowly organize

By: Dr. Jeff Masters , 7:17 PM GMT on June 28, 2010

Share this Blog
2
+

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

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 907 - 857

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65Blog Index

Noticed the weakness in the steering layer as well. This thing definitely has room to slide a little further north than forecast. The GFS, CMC and GFDL definitely accounted for this in previous runs. However, the abrubt shift of these models to the south earlier today left me scratching my head. Still think they were on to something.
Member Since: Posts: Comments:
Guys, maybe it's just me but I see a new center at 91.6W, 20.9N ... Does anybody see this, it's the last frame of the visible. A center fix to the NE?

Member Since: Posts: Comments:
Quoting Tazmanian:



time for some in new i had it with the old one
Ok. Anyways why did you take like 50 pictures of stoplights?
Member Since: September 2, 2009 Posts: 130 Comments: 21091
StormW, Please explain your statement. I don't think some understand.
Nevermind, you already did.
Member Since: Posts: Comments:
Quoting Tazmanian:



time for some in new i had it with the old one
Quoting StormW:


Hanna, take a look out west, north of the four corners, that's a very small ridge...look to the east of ALEX...Strong ridge...look north of, and in between Alex....what do you see?
I see a big gapping hole that isnt good at all.
Member Since: Posts: Comments:
902. xcool
kmanislander SO TRUE.
Member Since: Posts: Comments:
hey all i no whats ues Alex has a yo-yo
Member Since: Posts: Comments:
Ma nature been setting this stage for a week..

And now it just may be showing some flavor..as the Circulation again shows it true size.

Member Since: July 3, 2005 Posts: 420 Comments: 127546
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.
Member Since: August 19, 2006 Posts: 0 Comments: 15725
Quoting MiamiHurricanes09:
Stage 1 of developing a CDO.


again... lol
Member Since: Posts: Comments:
what does that mean storm not good
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Taz why did you change you avatar? The other one was a classic.



time for some in new i had it with the old one
Member Since: Posts: Comments:
Quoting gator23:

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


I'm not sure you mean. Do you mean bloggers from here? If not, WU uses the exact NHC forecast.
Member Since: Posts: Comments:
Quoting TampaSpin:


Exactly StormW....posted that a few minutes ago....JUST SAYIN

details puh-lease
Member Since: Posts: Comments:
Quoting 92Andrew:


Thanks for the video Levi! Very informative. Definitely have a better grip on the situation as a result of watching it. Thanks again!!


You're welcome, and thank you :)
Member Since: Posts: Comments:
888. xcool
TampaSpin KEEP UP GOOD WORK..
Member Since: Posts: Comments:
Quoting Tazmanian:
TS today cat 5 tonight
Taz why did you change you avatar? The other one was a classic.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
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.

As long as he doesn't stay that way and travel up the mississippi river and hit Saint Louis! Hey no one has forecasted that yet!
Member Since: Posts: Comments:
Quoting Weather456:
Blog Update from this morning

LINK
good afternoon weather456.
Member Since: Posts: Comments:
Quoting StormW:
THIS is not good.



Hi Storm, can you explain a bit more about what you mean?
Member Since: Posts: Comments:
Data from the recon coming into Alex's NW quad at the 400mb level indicates that wind shear over the storm associated with the trough over the north gulf coast is lessening. The NW winds associated with the trough switch to NNE on the outskirts of the storm, and this is confirmed on satellite imagery, where upper clouds are no longer moving towards the center of Alex in the NW quad the same pronounced way like they were this morning.

Member Since: Posts: Comments:
Quoting StormW:
THIS is not good.



YIKES when did that come out!
Member Since: May 27, 2009 Posts: 0 Comments: 4436
Quoting StormW:
THIS is not good.



Exactly StormW....posted that a few minutes ago....JUST SAYIN
Member Since: Posts: Comments:
TS today cat 5 tonight
Member Since: Posts: Comments:
861. Lighten up!
Member Since: Posts: Comments:
Blog Update from this morning

LINK
Member Since: Posts: Comments:
876. xcool
StormW .NOPE
Member Since: Posts: Comments:
Quoting CybrTeddy:
-80C cloudtops directly over the COC.
Stage 1 of developing a CDO.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting helove2trac:
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
Its not moving east its moving to the north/nnw right now.
Member Since: Posts: Comments:
Quoting GlobalWarming:


Reported.

why?
Member Since: Posts: Comments:
yup
Member Since: Posts: Comments:
Quoting StormW:


Now that's a weakness!
I didn't see one like that even when Darby was a CAT 2. Pretty crazy stuff there.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
869. xcool
I have to throw it out FORECAST MODELS
Member Since: Posts: Comments:
Quoting oddspeed:
okay this is getting crazy... there are totally two distinct separate centers now!


I dont think so Coop...
Member Since: Posts: Comments:
Quoting StormW:


Now that's a weakness!

Oh wise one, please explain...
Member Since: Posts: Comments:
Quoting oddspeed:
okay this is getting crazy... there are totally two distinct separate centers now!


How do you figure that?
Member Since: Posts: Comments:
863. xcool
StormW YEAH BIG TIME. MEANING MORE NNW
Member Since: Posts: Comments:
Quoting Hurricanes101:


yea cuz tropical systems wait for the NHC to give the go ahead before they intensify lol
Lol, you got a good point though.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Levi32:
From a few hours ago:

Tropical Tidbit for Monday, June 28th, with Video


Thanks for the video Levi! Very informative. Definitely have a better grip on the situation as a result of watching it. Thanks again!!
Member Since: Posts: Comments:
Quoting RecordSeason:
801:

No I got what you were saying.

You were implying that I am a wishcaster or doomcaster.

However, in this instance, I honestly believe I am correct.
I, as a met and long-term poster here, see nothing to support rapid intensification or, ultimately, eastward movement.

What have you seen to support such a notion?
Member Since: August 16, 2007 Posts: 6 Comments: 12461
ALEX aviationweather.gov/adds/satellite
Member Since: July 3, 2005 Posts: 420 Comments: 127546

Viewing: 907 - 857

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
71 °F
Mostly Cloudy