Alex building an eyewall, still not a hurricane

By: Dr. Jeff Masters , 7:34 PM GMT on June 29, 2010

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Tropical Storm Alex is slowly building an eyewall, which is now more than 50% complete, according to recent satellite imagery and microwave images (Figure 1.) Satellite loops show a slot of dry air is spiraling into the center of the storm, and until this dry slot gets closed off, Alex will not be able to intensify significantly. Alex's heavy thunderstorms and low level spiral bands continue to slowly increase, but upper-level outflow is mediocre to the north and east, and absent elsewhere. The Hurricane Hunters are in the storm and have not found any hurricane-force winds at the surface yet.


Figure 1. Microwave "radar in space" image taken at 10:11 am CDT Tuesday June 28, 2010, showing that Alex had built an eyewall a little more than 50% complete. Image credit: Navy Research Lab.

Impacts
Alex is already bringing bands of heavy rain to the coasts of Texas and Mexico, as seen on the Brownsville, Texas radar. Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Since Alex is a large storm, it will have a storm surge that will affect most of the South Texas coast. NHC is giving a 40% - 60% chance of a storm surge of at least 3 feet affecting the Brownsville area, and 10% - 30% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the South Texas coast (Figure 2.) However, Alex is now unlikely to get that strong, and the surge should be less. Flooding damage from the expected 6 - 12 inches of rain from Alex will also be a major concern, as will wind damage. The combined wind, surge, and flooding damage from 2008's Hurricane Dolly, which hit near Brownsville, were about $1.05 billion. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall. I expect Alex will be similar in its impacts to Dolly, though Alex's storm surge damage is likely to be greater. If Alex hits more than 50 miles south of the Texas border, as currently appears likely, the damage will be far less, since this region of the coast is relatively sparsely populated.


Figure 2. Maximum Water Depth (storm tide minus the elevation of the land it is passing over) computed using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. The "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of five feet above mean sea level, and the combined storm surge and tide (the "storm tide") is ten feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide, and thus shows the worst-case inundation scenarios for a mid-strength Category 2 hurricane moving WNW at 5 mph. For more information on storm surge, consult our detailed storm surge pages.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models confirm the faster movement of Alex to the coast, and residents in the affected areas now have 12 hours less to prepare for Alex's arrival than it seemed with yesterday's forecasts. Conditions will begin to deteriorate along the coast late tonight, so today is the day to finish preparations if you live near the Texas/Mexico border! The ridge that is steering Alex to the northwest is expected to strengthen today and Wednesday, which should push Alex on a more west-northwest and then westerly track on Wednesday. A few models even have Alex moving west-southwest by the time it makes landfall. The most northerly landfall location, near Brownsville, is predicted by the HWRF model.

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 4am CDT (9 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 88% chance of tropical storm conditions (winds 39+ mph), 23% 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.

Corpus Christi, TX: 42% tropical storm, 1% hurricane.

La Pesco, MX: 37% tropical storm, 3% hurricane.

Freeport, TX: 18% tropical storm, 0% hurricane.

Tampico, MX: 14% tropical storm, 0% hurricane.

Galveston, TX: 13% tropical storm, 0% hurricane.

Intensity forecast for Alex
Alex is over a region of ocean with a warm, clockwise rotating Loop Current eddy that broke off from the Loop Current in July 2009 and moved west-southwest over the past 11 months. This eddy has moderately high total ocean heat content . Wind shear has fallen to a low 5 knots, and is projected by the SHIPS model to remain in the low range, below 10 knots, this afternoon and Wednesday. The combination of low wind shear and moderately high ocean heat content should allow Alex to intensify into a Category 1 hurricane, but time is running out for it to be a Category 2 hurricane. NHC is giving Alex a 79% chance of being a hurricane on Wednesday morning, and a 4% chance it will be a major hurricane at that time. Water vapor satellite images show the amount of dry air over the western Gulf of Mexico has decreased over the past day, though as I noted above, the dry slot wrapping into Alex's core is currently keeping the storm from closing off an eyewall. Dry air may turn out to be an increasing detriment to Alex on Wednesday as the storm approaches land. 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. I don't expect Alex to stall out again, so slow motion leading to upwelling of cold water will probably not be a problem for Alex. The main issue limiting intensification will be the fact that Alex is so large, and it takes more time for a large storm to organize. Thus, I think Alex has only a 10% chance of intensifying into a major hurricane before landfall.

Elsewhere in the tropics
The last few runs of the NOGAPS model have been predicting the formation of a tropical disturbance off the coast of Nicaragua on Friday or Saturday that will move northwestward towards western Cuba. The GFS model, and the two models that use it for starting conditions, the GFDL and HWRF, are indicating the possibility that a weak extratropical storm may form along coastal Alabama this weekend. It is unlikely that such a storm would be over water long enough to transition to a tropical storm.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex's winds will not directly affect the oil slick location. However, because Alex is such a deep low pressure region, strong southeast to south winds of 10 - 20 knots will blow over the oil slick region today through Thursday, 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. Alex is currently bringing swells of 3 - 4 feet to the coastal regions impacted by the oil slick, and these swells will increase to 6 - 8 feet on Wednesday. Wave heights will increase to 5 - 7 feet on Wednesday. Alex is expected to bring a storm surge of 1 - 2 feet along the coast in the oil spill region. The swells and waves that will accompany these high water levels will act to push oil deep into the marshlands in some locations. The long range forecast for the oil slick region is uncertain, due to the possibility a weak area of low pressure might develop late this week along the remains of a cold front draped across the region.

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

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Alex
2) A look ahead at what may happen the rest of hurricane season

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update Wednesday morning by 9:30am CDT. Rob Carver is planning on doing a late-night update tonight.

Jeff Masters

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1893. will45
I tell ya guys it looks like this year weaknesses arnt what they used to be
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1892. Ossqss
Just watch out for the curve balls? just sayin -- Out>>>>>>
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Quoting scott39:
Hypothetically, Just to make sure I understand, If a TC stalls and there is a weakness in the high pressure, it gravitates toward the weakness?
Regardless of stalling a weakness attracts a tropical cyclone or area of low pressure. What stalling does is let other factors (such as troughs, ridges, etc...) happen without having an affect on the system which in turn changes the track greatly.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Orcasystems:
If I had to guess....
I would put landfall at La Pesca or just south of it.


Oh oh.... now all of the models are pointing at them.
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1889. Patrap
Quoting SavannahStorm:


Yea, the G-IV better watch out on its next run. Alex is running out of recon planes to pick on.


Dats a really bad trend.

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Quoting centex:
Correct, but unfortunately we will not know because of recon issues. I was really looking forward to +1 hour fix for several reasons, track, pressure, wind speed. No TS has had this low of pressure, may not see again in our lifetime.


I hope we don't see it again in our lifetime, unless of course its a fish storm.
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1793 Rita Evac: YES!!!! YEs! I see what you are looking at on that Radar. THat is a vortex at the 4:30 - 5:00 way at the edge. Being at the edge it must be way up in the atmo.

The motion does seem SW to SSW. At least she is still moving...

Everyone go look at what Rita found!
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10pm

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Hurricane Alex!

Very informative sentence from the hurricane center:

"ALEX WILL BEGIN TO WEAKEN AFTER ITS
CENTER CROSSES THE COASTLINE."

No really?! Never woulda guessed...
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Link
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NO STATIONARY!
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1882. Patrap
Brownsville best Hope that New Burst dosent become dominate and the older one spin Out and well..




Pfft,ALEX hasnt a History of that does he?



Bueller?

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Quoting Patrap:
Last Night the P3 NOAA went Pfffttt and had to return on 3 Turning instead of 4.

Now tonight the HH AF C-130 returns for Mechanical.

I dont like the Trend.
Alex is a bad seed.

Mean Kid.

Sneakie.


Yea, the G-IV better watch out on its next run. Alex is running out of recon planes to pick on.
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Well no stall but a slower motion.
Member Since: August 19, 2006 Posts: 0 Comments: 15948
the blog is moving too fast for me to keep up
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1878. Delsol
Quoting MiamiHurricanes09:
My funny little image, lol. I'm eager to see if the 03:00 UTC graph shows a larger weakness, which seems more probable.


So the ridge has weakened do you feel this is causing alex to stall? and will he head more north if the weakness is larger?
-
Man there really has been a windsheild wiper feeling to this storm... tracks trends more southernly by day and more north at night.
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
hmmm. wonder if we'll get a back round swell in west Fl.
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Radar failure while flying into a hurricane... they made the right choice by turning back.
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1874. scott39
Quoting kmanislander:


973 mbs, 65 knots
Hypothetically, Just to make sure I understand, If a TC stalls and there is a weakness in the high pressure, it gravitates toward the weakness?
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post 1600- you should have seen it while it was still in Africa. if it s the same one as the other day. it looked like a damn hurricane or strong tropical storm.lol!:)
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1872. centex
Quoting MrstormX:


Pressure is 972.9mb
Correct, but unfortunately we will not know because of recon issues. I was really looking forward to +1 hour fix for several reasons, track, pressure, wind speed. No TS has had this low of pressure, may not see again in our lifetime.
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Quoting NCHurricane2009:
Wow, Alex just won't be upgraded to a hurricane. I think it will at 11 PM because they said at 5 PM the satellite presentation (Dvorak numbers I believe) support a 65-knot (75 mph wind) hurricane, I think they are just waiting to get into the center with a recon plane to confirm winds have increased to 75 mph, which will happens shortly.

I mean, 980 mb is such a low pressure for a tropical storm, even for a broad circulation.


LOL, just as I said that in comment 1823, I see the pressure dropped to 972 mb, and Alex is now a hurricane. Comments are blowing up on the blog at the hurricane upgrade, LOL.
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1870. will45
another shift to the left
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So I guess it's super-official now.
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1868. Patrap
Last Night the P3 NOAA went Pfffttt and had to return on 3 Turning instead of 4.

Now tonight the HH AF C-130 returns for Mechanical.

I dont like the Trend.
Alex is a bad seed.

Mean Kid.

Sneakie.
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Pat, my skylight fix I spent all weekend on the roof, in 98 degree heat, didn't work. It rained today and my roof leaked more today than it did last time it rained. I laugh but it ain't frikkin' funny....LOL
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000
WTNT41 KNHC 300233
TCDAT1
HURRICANE ALEX DISCUSSION NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010
1000 PM CDT TUE JUN 29 2010

ALEX HAS GRADUALLY BECOME BETTER ORGANIZED ON SATELLITE IMAGES AND
DVORAK CLASSIFICATIONS FROM BOTH TAFB AND SAB CONTINUE TO SUPPORT A
CURRENT INTENSITY OF 65 KT. AN AIR FORCE RESERVE UNIT HURRICANE
HUNTER AIRCRAFT PASSED THROUGH THE CENTER ON A NORTHWEST TO
SOUTHEAST LEG AND MEASURED A CENTRAL PRESSURE OF 973 MB BY
DROPSONDE. THE SFMR ABOARD THE PLANE MEASURED A SURFACE WIND OF 62
KT JUST TO THE SOUTHEAST OF THE CENTER. SOON THEREAFTER...THE
AIRCRAFT HAD TO DEPART THE AREA DUE TO RADAR FAILURE. BASED ON THE
SUBSTANTIAL DROP IN CENTRAL PRESSURE SINCE EARLIER TODAY AND THE
FACT THAT HIGHER SURFACE WINDS ARE LIKELY OCCURRING IN THE
NORTHEAST QUADRANT...ALEX IS BEING UPGRADED TO A 65-KT HURRICANE
FOR THIS ADVISORY. VERTICAL SHEAR IS FORECAST TO REMAIN BELOW 10
KT FOR THE NEXT 24-48 HOURS SO THE HURRICANE SHOULD REMAIN IN AN
ENVIRONMENT CONDUCIVE FOR INTENSIFICATION UP TO LANDFALL. THE
SHIPS RAPID INTENSIFICATION INDEX SHOWS A 33 PERCENT PROBABILITY OF
RAPID INTENSIFICATION...I.E. A 30-KT INCREASE OVER 24 HOURS.
HOWEVER...NONE OF THE OTHER NUMERICAL INTENSITY GUIDANCE SHOWS ALEX
STRENGTHENING BEYOND CATEGORY ONE STATUS PRIOR TO LANDFALL. THE
OFFICIAL INTENSITY IS VERY CLOSE TO THE LGEM GUIDANCE AND ABOUT THE
SAME AS THAT FROM THE PREVIOUS PACKAGE.

ALEX WOBBLED WESTWARD OVER THE PAST SEVERAL HOURS. AFTER SOME
SMOOTHING...THE INITIAL MOTION ESTIMATE IS 280/8. SHORT-TERM
FORECASTS FROM DYNAMICAL MODELS SUCH AS THE GFDL AND GFS SUGGEST
THAT THE WESTWARD MOTION IS TEMPORARY AND THAT A WEST-NORTHWESTWARD
TRACK SHOULD RESUME SOON. THE FLOW TO THE SOUTH OF A MID-
TROPOSPHERIC RIDGE SHOULD STEER THE HURRICANE ON A GENERALLY
WEST-NORTHWESTWARD COURSE ACROSS THE WESTERN GULF OF MEXICO...WITH
ALEX REACHING THE COAST IN ABOUT 24 HOURS. BECAUSE OF THE JOG TO
THE LEFT...THE NEW NHC FORECAST TRACK HAS BEEN SHIFTED SLIGHTLY TO
THE SOUTH OF THE PREVIOUS ONE. IT SHOULD BE REPEATED THAT ONE
SHOULD NOT FOCUS ON THE EXACT PREDICTED LANDFALL POINT BECAUSE OF
TRACK FORECAST UNCERTAINTIES...AND ALSO BECAUSE THIS IS A LARGE
TROPICAL CYCLONE.

FORECAST POSITIONS AND MAX WINDS

INITIAL 30/0300Z 23.1N 94.8W 65 KT
12HR VT 30/1200Z 23.7N 96.0W 75 KT
24HR VT 01/0000Z 24.2N 97.6W 80 KT
36HR VT 01/1200Z 24.6N 99.2W 55 KT...INLAND
48HR VT 02/0000Z 24.5N 101.0W 30 KT...INLAND
72HR VT 03/0000Z...DISSIPATED INLAND

$$
FORECASTER PASCH


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Quoting Patrap:
Evening to yas ms..
Welcome to the Premiere of the 2010 Season.

Pass the Napkins and theres a seat down up front nearer the screen.

The Previews are bout over.


LOL! they sure are.

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Quoting mobilebayal:


Interesting facts about Hurricane Tip, 1900Hurricane. An amazing storm with an 870 sea level pressure and peak winds of 190mph. Thanks for sharing. I sure hope I never see anything like Tip in the Gulf!

Yeah, no problem! Glad you enjoyed it. :)
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1862. angiest
Movement West 9.
Member Since: August 26, 2006 Posts: 16 Comments: 4766
Quoting kmanislander:


973 mbs, 65 knots
Impressive pressure for a minimum category 1.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1859. Patrap
With a sigh of Heavy Optimism

The Atlantic Spits Out a CV Like Thing in late June that can only lead to one easy conclusion

Hurricane ALEX is her.

Strap in and enjoy a Cold Fresca.

The Season of Hyperactivity has begun



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we officially have a hurricane kids!
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Now a Hurricane.
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Lotsa fish storms in 1995.
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Quoting MiamiHurricanes09:
And so we beat 2005.

...ALEX BECOMES THE FIRST HURRICANE OF THE 2010 SEASON AND THE FIRST JUNE ATLANTIC HURRICANE SINCE 1995...


973 mbs, 65 knots
Member Since: August 19, 2006 Posts: 0 Comments: 15948
dang the blog didn't blow up. hurricane alex
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1852. will45
looks like NHC showing hurricane Alex now
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And so we beat 2005.

...ALEX BECOMES THE FIRST HURRICANE OF THE 2010 SEASON AND THE FIRST JUNE ATLANTIC HURRICANE SINCE 1995...
Member Since: September 2, 2009 Posts: 130 Comments: 21194
I beat all of you too it mwuah ha ha
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1848. Hhunter
hurricane....breaking news
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Quoting Patrap:


Wow, that radar made me check some of the buoy readings, some of them just off the LA coast are already getting TS strength gusts...

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Alex is now officially a Hurricane.

...ALEX BECOMES THE FIRST HURRICANE OF THE 2010 SEASON AND THE FIRST JUNE ATLANTIC HURRICANE SINCE 1995...
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Quoting JLPR2:

Just looking pretty, that's all


More and more like a butterfly.

Quoting Xyrus2000:
Well super typhoon tip was around 1380 miles in diameter while Alex is probably around 700 miles in diameter depending on how you measure it.


By this, it looks like it's 25 degrees wide by latitude, or about 1,700 miles. But that's only if you count the outer bands.



CIMSS shows Alex as a hurricane.
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Confirmed by NHC
000
WTNT31 KNHC 300231
TCPAT1
BULLETIN
HURRICANE ALEX ADVISORY NUMBER 18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012010
1000 PM CDT TUE JUN 29 2010

...ALEX BECOMES THE FIRST HURRICANE OF THE 2010 SEASON AND THE FIRST
JUNE ATLANTIC HURRICANE SINCE 1995...

SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...23.1N 94.8W
ABOUT 195 MI...315 KM ESE OF LA PESCA MEXICO
ABOUT 255 MI...415 KM SE OF BROWNSVILLE TEXAS
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/HR
PRESENT MOVEMENT...W OR 280 DEGREES AT 9 MPH...15 KM/HR
MINIMUM CENTRAL PRESSURE...973 MB...28.73 INCHES


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Quoting scott39:
What does that mean in reference to Alex?
Weaknesses tend to attract areas of low pressure. I'm sure Kman can explain better, I'm just stating the basics. :)
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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