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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what's the deal with the convection smack dab in the middle of the gulf. it doesn't seem to be part of Alex.
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Quoting cg2916:


Only 22 mph at the surface?


Yup, its a long way from the center and winds can drop very dramatic from the center of the storm.
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Quoting DestinJeff:
I remember commenting that 18Z XTRP would be toward Galveston Bay ... there you go:

Link

I know that XTRP "is not a model". I get it, trust me. The thing that interests me is the gap between XTRP and model consensus, and the point at which it ensues. In this case, you can see gap starts immediately. To me that indicates some funky model solutions, especially given Alex's propensity to drift more North than West during his near-stall.

Soon enough you will see the need for a "hard left turn" for Alex to meet forecast estimated landfall if he doesn't take on more of a weterly component.

That's just it, GFDL, and others have been calling for the stall and northerly drift for days, now. And, yes, a later hard left turn.

Have since relaxed that solution, somewhat.
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154. Daveg
I know I'm still learning, but watching all the data that is being posted.

It would seem to be that the models will probably go back north again to where they were, and the one cycle of hard left turning models will be an anomaly.

Again, just a noob thinking out loud (probably dangerous!!). :-)
Member Since: September 23, 2005 Posts: 0 Comments: 426
Quoting cg2916:
Models starting to separate again:

Early Statistical:



Early Dynamical:



Late Dynamical:



hmmmmm...I think even the models are confused...:)
Member Since: July 2, 2009 Posts: 0 Comments: 2811
The ridge over the GOM is pretty steady. Fluctuations in BP are normal but are meaningless in the long run. Alex is heading N. Mex., S Texas. Face it.
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Quoting cg2916:


Only 22 mph at the surface?


Notice the location of that data: 25.9N 88W. That's not near the center of the storm, it's in the outer band.
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18z Early Cycle NHC model tracks
Alex
Statistical/Simple Models (CLIPER,BAMs,LBAR,other Statistical Models)
Dynamic Models (More sophisticated models)




Dynamic Models (More sophisticated models)


Early Model Wind Forecasts

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Quoting cg2916:
Models starting to separate again:

Early Statistical:



Early Dynamical:



Late Dynamical:

Favoring the red one on the "early dynamical" run.
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Gotcha. Same here. Been watching these for a long time, but still no Met.
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Besides the "little sister" showing up on the GFDL plot, also interesting is that the GFDL carries Alex's remnants all the way over to the Cali/AZ border in the vortex following nest. Whacky. (right?)

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Models starting to separate again:

Early Statistical:



Early Dynamical:



Late Dynamical:

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Quoting Levi32:


Like I said, the SSE winds between 700mb and 400mb indicate that the ridge over the Gulf of Mexico is weakening and the mid-level steering currents are aligned in a way that would take Alex NNW right now, which he is trying to do but very slowly.

The new data from these planes should hopefully be put into the 0z model runs tonight, making them more accurate.


Thank you for your answer Levi...:)
Member Since: June 16, 2008 Posts: 0 Comments: 507
Quoting Patrap:
That older CoC is Toast as we see a newer overall center beginning to consolidate.




Where is the new center forming? I was wondering if it would do this...

When is this thing forecast to start moving again?
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Quoting Levi32:
Alex is not reforming his center....it is still very well-defined with a central pressure of a borderline hurricane. That kind of a center will not relocate somewhere else unless Alex completely falls apart and degrades to a tropical depression with no defined center. This is not that kind of a situation.
Exactly. I think it is highly unlikely to near impossible for a COC of that strength to relocate.
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Conditions are only suportive for slow development for now.However,on Tuesday,Wensday,and mabye even Thursday,heat content will be very high,wind shear will be even lower,and the air will be very moist and unstable.Rapid intensification could easily occur during this time.This could allow Alex to become at least a Cat 2 hurricane.I hope you this this is reasonable:)
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Quoting hurricaster:
Pat, what are you estimated coordinates of the new COC. Been watching this as well.


I dont dare do that in this jungle..

Im tough..but I aint Clint Eastwood.

Somewhere in the Middle of the Mean Convective Blow ups..


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What is Pat smoking??
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Agree, feel like the entire system is drifting NNW. This is a weird one. Gotta love June.
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Lots of "you know who" talk on the blog. What happened? Please don't answer on the blog just send me a Wu-mail. Thanks.
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Alex is not reforming his center....it is still very well-defined with a central pressure of a borderline hurricane. That kind of a center will not relocate somewhere else unless Alex completely falls apart and degrades to a tropical depression with no defined center. This is not that kind of a situation.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting truecajun:
forgive me if this is a stupid question, but is that blob of convection NE of Alex anything to worry about spinning up in the future?


North of rather than NE, sorry.
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Quoting Patrap:
That old Coc is Toast as we see a newer overall center beginning to consolidate
If that's the case, the models will really be thrown for a loop lol
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From the "old" blog...

Just a quick question for those in the know. Alex took a while trying to decide if it wanted to develop and has slowly wandered more than once. Is there reason to believe, whether it's MX or TX, that it will speed up once it gets a bit north? Because it's so slow and so big, the amount of rain could be large, widespread and devastating.
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Pat, what are you estimated coordinates of the new COC. Been watching this as well.
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There is no sign at all that the COC is changing. And you wouldn't expect that in a storm like this anyways. The storm is behaving exactly as expected. And is starting to build back up, piling on some serious convection and drawing it closer to the center (despite the moderately dry air to the NW)
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Quoting StormSurgeon:


NW at 5, you think?


The envelope is maybe drifting nnw,..the next few Hours a new Motion and speed should shake out as well.

As per da Plane
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Quoting Joanie38:


What does that mean EXACTLY Levi??? Sorry trying to learn..:)


Like I said, the SSE winds between 700mb and 400mb indicate that the ridge over the Gulf of Mexico is weakening and the mid-level steering currents are aligned in a way that would take Alex NNW right now, which he is trying to do but very slowly.

The new data from these planes should hopefully be put into the 0z model runs tonight, making them more accurate.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Still no sightings of Cantore? ;)
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Quoting Hurricanes101:


This is not a recon plane, this is the plane that lets us know what kind of steering is in place


Oh.

Quoting help4u:
Only one dynamic model takes it into texas now.


Did they move south or north?
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forgive me if this is a stupid question, but is that blob of convection NE of Alex anything to worry about spinning up in the future?
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Why is the page loading so big? never happened before?
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Quoting cg2916:


Only 22 mph at the surface?


Look at my picture and observe how far away that dropsonde is from Alex. It's out in the central gulf....this is an investigation of conditions aloft not a mission into Alex.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting will45:


Looks slim now but if i lived anywhere on the Gulf Coast i would keep an eye on the progress.Weird things have happened with these storms.
We could really use it here, as long as it isn't too strong. We really need the rain.
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Quoting Patrap:
That old Coc is Toast as we see a newer overall center beginning to consolidate


This is almost making as many new centers as 90L! LOL
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Quoting cg2916:


Only 22 mph at the surface?


This is not a recon plane, this is the plane that lets us know what kind of steering is in place
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Quoting Patrap:
Floater - Rainbow Color Infrared Loop


NW at 5, you think?
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Only one dynamic model takes it into texas now.
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Link to friendly local neighbourhood buoy 42005.
Steady tendency ...slowly dropping p and slowly rising wind.



Link
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Quoting Levi32:
Hurray! G-IV NOAA 49 in the air dropping loads of dropsondes over the gulf. 0z runs should hopefully have this new data in them.

Latest drop at 25.9N 88W is showing SSE winds from the 700mb level upward until they turn SW in Alex's outflow. This is indicating the weakness in the ridge and mid-level steering currents that are trying to take the storm NNW.

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1011mb (29.85 inHg) Sea Level (Surface) 26.0°C (78.8°F) 25.6°C (78.1°F) 65° (from the ENE) 19 knots (22 mph)
1000mb 96m (315 ft) 25.2°C (77.4°F) 24.9°C (76.8°F) 70° (from the ENE) 20 knots (23 mph)
925mb 781m (2,562 ft) 21.8°C (71.2°F) 20.3°C (68.5°F) 95° (from the E) 20 knots (23 mph)
850mb 1,514m (4,967 ft) 18.0°C (64.4°F) 16.3°C (61.3°F) 115° (from the ESE) 17 knots (20 mph)
700mb 3,154m (10,348 ft) 9.0°C (48.2°F) 8.2°C (46.8°F) 155° (from the SSE) 22 knots (25 mph)
500mb 5,880m (19,291 ft) -4.3°C (24.3°F) -5.3°C (22.5°F) 155° (from the SSE) 26 knots (30 mph)
400mb 7,610m (24,967 ft) -13.5°C (7.7°F) -15.4°C (4.3°F) 160° (from the SSE) 25 knots (29 mph)

300mb 9,740m (31,955 ft) -27.5°C (-17.5°F) -30.6°C (-23.1°F) 195° (from the SSW) 13 knots (15 mph)
250mb 11,030m (36,188 ft) -37.5°C (-35.5°F) -41.0°C (-41.8°F) 225° (from the SW) 15 knots (17 mph)
200mb 12,520m (41,076 ft) -50.3°C (-58.5°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 240° (from the WSW) 15 knots (17 mph)
150mb 14,350m (47,080 ft) Height extrapolated since sonde was released within 25mbs below this level.




What does that mean EXACTLY Levi??? Sorry trying to learn..:)
Member Since: June 16, 2008 Posts: 0 Comments: 507
So are we in the clear here in Houston/Galveston?? Looks like it, right??
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Quoting Levi32:
Hurray! G-IV NOAA 49 in the air dropping loads of dropsondes over the gulf. 0z runs should hopefully have this new data in them.

Latest drop at 25.9N 88W is showing SSE winds from the 700mb level upward until they turn SW in Alex's outflow. This is indicating the weakness in the ridge and mid-level steering currents that are trying to take the storm NNW.

Level Geo. Height Air Temp. Dew Point Wind Direction Wind Speed
1011mb (29.85 inHg) Sea Level (Surface) 26.0°C (78.8°F) 25.6°C (78.1°F) 65° (from the ENE) 19 knots (22 mph)
1000mb 96m (315 ft) 25.2°C (77.4°F) 24.9°C (76.8°F) 70° (from the ENE) 20 knots (23 mph)
925mb 781m (2,562 ft) 21.8°C (71.2°F) 20.3°C (68.5°F) 95° (from the E) 20 knots (23 mph)
850mb 1,514m (4,967 ft) 18.0°C (64.4°F) 16.3°C (61.3°F) 115° (from the ESE) 17 knots (20 mph)
700mb 3,154m (10,348 ft) 9.0°C (48.2°F) 8.2°C (46.8°F) 155° (from the SSE) 22 knots (25 mph)
500mb 5,880m (19,291 ft) -4.3°C (24.3°F) -5.3°C (22.5°F) 155° (from the SSE) 26 knots (30 mph)
400mb 7,610m (24,967 ft) -13.5°C (7.7°F) -15.4°C (4.3°F) 160° (from the SSE) 25 knots (29 mph)

300mb 9,740m (31,955 ft) -27.5°C (-17.5°F) -30.6°C (-23.1°F) 195° (from the SSW) 13 knots (15 mph)
250mb 11,030m (36,188 ft) -37.5°C (-35.5°F) -41.0°C (-41.8°F) 225° (from the SW) 15 knots (17 mph)
200mb 12,520m (41,076 ft) -50.3°C (-58.5°F) Reading usually unavailable when air temperature is below -40°C (-40°F) 240° (from the WSW) 15 knots (17 mph)
150mb 14,350m (47,080 ft) Height extrapolated since sonde was released within 25mbs below this level.




Only 22 mph at the surface?
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That older CoC is Toast as we see a newer overall center beginning to consolidate.


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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.