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: 57 - 7

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

Quoting Crawls:
Wow, blog has really slowed down! Where did everyone go?


I think everyone is getting tired of all the waiting....
Member Since: July 2, 2009 Posts: 0 Comments: 2811
I'm here, just don't have anything to add... :)
Member Since: Posts: Comments:
Everyone went to mexico.
Member Since: Posts: Comments:
Quoting scottsvb:
actually the longer it sits in the BOC the further south Alex will go. Ridging start digging down late Tuesday into Weds that will turn Alex west. 23N 24N or 25N before the turn? Probably be about 200 miles south of the Tx border.


I agree as soon as the weakness fills back in he wont go north
Member Since: Posts: Comments:
actually the longer it sits in the BOC the further south Alex will go. Ridging start digging down late Tuesday into Weds that will turn Alex west. 23N 24N or 25N before the turn? Probably be about 150-200 miles south of the Tx border.
Member Since: January 22, 2006 Posts: 0 Comments: 1689
I wish it would just hurry and decide what it is going to do. All this back and forth and it just sitting there is just frustrating......
Member Since: July 2, 2009 Posts: 0 Comments: 2811
Wow, blog has really slowed down! Where did everyone go?
Member Since: Posts: Comments:
Link
Member Since: Posts: Comments:
actually the longer it sits in the BOC the further south Alex will go. Ridging start digging down late Tuesday into Weds that will turn Alex west. 23N 24N or 25N before the turn? Probably be about 150-200 miles south of the Tx border.
Member Since: January 22, 2006 Posts: 0 Comments: 1689
Quoting help4u:
Alex sounds like it is toast.


And why would you say that? I think it is quite the opposite.
Member Since: Posts: Comments:
Quoting NRAamy:
thanks for tehs econd update, doc

bud sir....


hee hee *giggle*
Member Since: Posts: Comments:
GFDL 12Z RUN:
http://moe.met.fsu.edu/cgi-bin/gfdltc2.cgi?time=2010062812-alex01l&field=Sea+Level+Pressure&hour=An imation
Member Since: Posts: Comments:
35mph gust east of Corpus Christi/South of Louisiana, way out there
Member Since: Posts: Comments:
Quoting NRAamy:
thanks for tehs econd update, doc

bud sir....


He sure cant hide it can he Amy lol?
Member Since: Posts: Comments:
Thank-you very much...I appreciate your input and expertise!


Quoting Levi32:


I found it odd but the pattern is actually favoring a possible trough-split off the SE US coast so I wouldn't rule out the possibility of some mischief in that area in 5-8 days, but we'll have to see if the models remain consistent on lowering pressures in the area.
Member Since: Posts: Comments:
What do the yellow arrows in the ascat designate
Member Since: Posts: Comments:
thanks for tehs econd update, doc

bud sir....
Member Since: Posts: Comments:
Quoting Skyepony:
Very well defined tight circulation.
Member Since: Posts: Comments:




Member Since: Posts: Comments:
33. Asta
Thanks Dr. Masters!
Member Since: Posts: Comments:
32. Skyepony (Mod)
Member Since: Posts: Comments:
Quoting portcharlotte:
Levi32, possibly you have already addressed this but I missed it if you did..What do you make of the GFDL run showing low pressure developing over the East Gulf in 5 days?


I found it odd but the pattern is actually favoring a possible trough-split off the SE US coast so I wouldn't rule out the possibility of some mischief in that area in 5-8 days, but we'll have to see if the models remain consistent on lowering pressures in the area.
Member Since: November 24, 2005 Posts: 635 Comments: 26652
Alex sounds like it is toast.
Member Since: Posts: Comments:
I was thinking the same thing, bassis, "Unfortunately?" What does GlobalWarming want this thing to do?
Member Since: Posts: Comments:
" 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."

Yeah well....big 200mb ridge = good thing for Alex, not bad. High temperatures at that height indicate a big heat buildup due to release of latent heat which pumps the upper anticyclone over the system. Hurricanes are not necessarily more apt to intensify when the very upper levels of the troposphere are cold....in fact most of the time it is the opposite, especially for mature storms.
Member Since: November 24, 2005 Posts: 635 Comments: 26652
Celia refuses to die! Drifting east now
Member Since: Posts: Comments:
Quoting GlobalWarming:


nothing to worry about, unfortunately.
Why unfortunatly? thats good its nothing to worry about.
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:
Quoting GlobalWarming:


nothing to worry about, unfortunately.


Unfortunately??
Member Since: Posts: Comments:
Quoting alexhurricane1991:
Yep should be a steady heading now and a turn to the northwest later today.


I was about to correct that to a drift. Took another look at another loop and there is not much in it at this time.
Member Since: Posts: Comments:
Thank you Dr. Masters so what it sounds like to me its stalling/ slowly drifting due to its starting to feel the trof that will take it north alittle. So im assuming by later tonight he should pick up foward speed and head NNW again? Someone wanna help me out with this lol
Member Since: Posts: Comments:
Quoting kmanislander:
Alex appears to have resumed a slow motion to the NNW.
Yep should be a steady heading now and a turn to the northwest later today.
Member Since: Posts: Comments:
Alex is gonna do what he wants to. I am afraid he is going to hit that warm water and just explode.
Member Since: Posts: Comments:
Thank you doc., Afternoon all
Member Since: Posts: Comments:
Quoting Hurricane1956:
Hello everybody,what is that big swirl to the East of South Florida is that the remanants of invest 94L?,or a upper level low trying to develop?,is moving very fast toward Florida straight west bound and picking up some clouds,any comments about this feature?.Thanks!!!

Not 94L but the upper low that was to it's west. Not the slightest hint of surface rotation and you can see that on the visible. Also to me it looks like it's turning NW then N.
Member Since: Posts: Comments:
12z NAEFS, just south of the border.

Member Since: November 24, 2005 Posts: 635 Comments: 26652
.
Member Since: Posts: Comments:
Thanks for the update, Dr. M!
Member Since: Posts: Comments:
REPOST

Quoting winter123:

GFS trying to develop the wave coming off now. As a fish


Betcha that same trough that's trying to get Alex will get that one, or maybe the next trough in line on the west coast.

Member Since: Posts: Comments:
10. WAHA

According to 850 millibar vorticity maps, it looks like a piece broke off Alex and is rotating. If you can't see the image, click here.
Member Since: Posts: Comments:
Basically the stronger it gets the more poleward it will go... meaning the ridge would have to be stronger to push it to the west.
Member Since: Posts: Comments:
Thanks Dr. Masters! :)
Member Since: Posts: Comments:
Yeah stay tuned! The harder it is to pinpoint where it goes, at least that is my line of thinking.
Member Since: Posts: Comments:

Viewing: 57 - 7

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.