Category 2 Irene Approaches The Bahamas

By: Dr. Jeff Masters , 7:51 AM GMT on August 23, 2011

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As of 2am EDT, Hurricane Irene was located at 20.1N, 69.7W, 135 miles southeast of Grand Turk Island. It was moving west-northwest at 12 mph with maximum sustained winds of 100 mph, making it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 978 mb. Hurricane warnings have been issued for the northern coast of the Dominican Republic from the Haiti board to Cabo Engano, the southeastern and central Bahamas, and the Turks and Caicos islands. Hurricane watches have been posted for the north coast of Haiti from Le Mole, St. Nicholas to the Dominican border and the northwestern Bahamas. Tropical storm warnings are in effect for all of Haiti and the southern coast of the Dominican Republic from Cabo Engano to Santo Domingo.

5AM Update
As of 5am EDT, Hurricane Irene was located at 20.3N, 70.1W, 105 miles southeast of Grand Turk Island. It was moving west-northwest at 12 mph with maximum sustained winds of 100 mph, keeping it a Category 2 storm on the Saffir-Simpson scale. Irene has a minimum central pressure of 978 mb.

Figure 1 shows that Irene is maturing into a vigorous storm, with apparent waves in the western edge of the cirrus outflow.


Figure 1 IR satellite view of Irene taken at 135AM EDT, August 22, 2011

Track Forecast

Irene is forecast to move to the north-northwest, passing over all of the Bahama islands by Thursday evening, at which points it starts curving to the north. Irene is forecast to make landfall in the US near Wilmington, NC Saturday evening. However, it is important to note that this is not a definitive forecast, the average forecast error for day 5 is 250 miles. The timing of Irene's recurvature depends on how quickly several small troughs of low pressure in the Northeastern US move to the east. After Saturday, Irene may pose a threat to the mid-Atlantic coastline and locations further north, but it is too early to make a skillful forecast for those regions.

NHC is forecasting for Irene to become a major hurricane (winds faster than 110 mph), within 24 hours, then reaching peak intensity at 130 mph (Category 4 storm) by 8pm EDT Thursday evening.

Forecast models and adaptive observations
The different forecast models are in rough agreement until Irene nears the Carolinas. The dynamical hurricane forecasting models, GFDL and HWRF, have Irene making landfall near Charleston, SC. NGFDL (a variant of the GFDL that uses NOGAPS for background conditions) has landfall near Morehead City, NC, and the GFS has Irene crossing the Outer Banks. The UKMET forecast track splits the difference, placing Irene near Myrtle Beach, SC at landfall.

To reduce the model spread, and improve the track forecast error, the NOAA Gulfstream IV and an Air Force WC-130J have been flying dropsonde missions north of Irene. A dropsonde is an meteorological instrument package dropped from a plane that can tell you the vertical profile of temperature, pressure, moisture, and winds. By flying these missions, the dropsondes can improve all of the numerical weather prediction models initial picture of the atmospheres, which improves the forecast. Also, NHC has asked NWS offices in the southeastern US that launch weather balloons to do so every 6 hours instead of the normal 12 hour frequency.


Figure 2 Official track forecast of Irene as of 2am.

5AM update
The 00Z ECMWF forecast is available and Figure 3 shows the maximum wind speed over the next week for the eastern coast of the US. Green indicates tropical storm force winds, while yellow and orange are hurricane-force winds. The important thing is not to fixate on the predicted landfall location, but to see that Irene's winds will affect areas far away from landfall. The GFS, not shown, agrees with ECMWF that Irene will have a large area of tropical-storm force winds associated with it.

Figure 3 Maximum wind-speed in mph from the 00Z August 23 ECMWF forecast for the next week.

Impacts

In the immediate future, Irene is expected to have a significant impact on the Bahamas and surrounding islands. Hurricane force winds are forecast to reach the southeastern Bahamas and the Turks and Caicos sometime this afternoon or evening. These locations can also expect 5-10 inches of rain. Three to six inches of rain are forecast over northern Hispaniola, with isolated areas receiving up to 10 inches. This could lead to flash flooding and mudslides in mountaineous terrain. NHC is predicting a storm surge of 9-13 feet above normal tide level for the southeastern Bahamas and the Turks and Caicos.

Outside of the islands immediately impacted by Irene, it is my judgement that everybody living on the eastern coast of the US should monitor Irene and review their hurricane preparations over the next few days.

Dr. Masters will have a new blog entry this morning, and Angela Fritz will be covering the afternoon. I'll be back on third shift tonight.

Thanks for reading,

Dr. Rob Carver

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Quoting biff4ugo:
How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you know something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?

Does the cone include the width of the storm or just uncertainty about the path of the eye?


Wide shallow continental shelf offshore.The surge is directly proportional to the width of the shallow water, and inversely proportional to the depth. Essentially, hurricane force winds blowing onshore across tens of kilometers of shallow water pile up water along coasts. The stronger the wind, the shallower the water, and the greater the extent of shallow water, the higher the pile of water. In some cases it can exceed 2-5 meters. In Galveston, Isaac Cline, the chief meteorologist, measured a rise of sea level greater than 16 feet above mean sea level.
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Quoting MIsland321:
did it jut wobble west? looks like interaction with land may have caused it to?

That's what i saw.......
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1180. Drakoen
Quoting presslord:


Ok dude...this time I'm not jokin'....Ya think we're good?


You're still in the cone so no.
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Quoting stillwaiting:
that blob off jax looks like its starting to orgaize,man that would be a HUGE fly in the ôntment and if it develops throw all the models out and start over,it would be unpresidented,it sure looks highly suspect on high res loop from cod


It sure would be quite the wildcard. I saw it earlier today... will be interesting to see how they interact... provided it's still there in a couple days time.
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Quoting MyrtleCanes:


Is anyone considering that that higher terrain of the dominican may temporarily weaken her a hair and cause a westward drift today influencing the long term track a little westward. I think the east shifts may have plateaued or stopped and west tweaks may start, we'll see.

I still favor a Hazel/Bertha hybrid track and approach to NC/SC


Well the current longwave trough over the east coast is ejecting northeastward, so some rebuilding of the ridge to the north of Irene is currently occurring.

However, it's the second larger trough and how deep that digs that will determine the final track. I still don't think we can say much definitively at this time other than eastern NC is the best guess we have.

I will point to the refusal of the Texas ridge to break down as a positive for the eastern US, though it's going to be close no matter what.
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ok time to consider this

It looks like Irene is jogging a bit to the West and the forecast is for her to turn more northward. Now who is in agreement with me that this storm might move WNW right above Eastern Cuba and towards the Western Bahamas? This is what I think she will do and so I am now on the "Westward" boat track for the short term. I still am thinking of a landfall in South Carolina since she is so far south.

Link
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW YORK NY
1050 AM EDT TUE AUG 23 2011

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
THE FOCUS OF ATTENTION WILL BE THIS WEEKEND AS THE TRI-STATE AREA
MAY BE IMPACTED FROM TROPICAL CYCLONE IRENE. LATEST MODEL AND
FORECAST GUIDANCE CONTINUE TO SHOW THE AREA TO BE IN A REGION OF
CONCERN. THE KEY TO REMEMBER HERE IS TO NOT FOCUS ON THE EXACT STORM
TRACK...AS IMPACTS FROM A TROPICAL SYSTEM CAN BE FELT SEVERAL
HUNDRED MILES FROM THE CENTER...EVEN IF LANDFALL DOES NOT OCCUR
ACROSS THE FORECAST AREA. PLEASE REFER TO THE NATIONAL HURRICANE
CENTER FOR THE LATEST OFFICIAL FORECASTS AND ADVISORIES REGARDING
THIS SYSTEM.

THE UPPER TROF ASSOCIATED WITH THE COLD FRONT WILL MOVE OFF THE
EASTERN SEABOARD BY FRI MORNING WITH HIGH PRESSURE TO BRIEFLY FOLLOW
AT THE SURFACE. IT APPEARS THAT THE UPPER TROF WILL BE FAR ENOUGH
NORTH OF THE TROPICAL SYSTEM TO NOT KICK IT OUT TO SEA...BUT YET
PROVIDE ENOUGH OF A WEAKNESS IN THE UPPER RIDGE TO THE SOUTH TO
ALLOW THE SYSTEM TO TRACK NORTH. AT THIS POINT IN TIME...THERE IS
SUFFICIENT UNCERTAINTY IN THE FORECAST TRACK.
ONCE AGAIN...PLEASE
REFER TO THE NATIONAL HURRICANE CENTER FOR OFFICIAL FORECASTS AND
ADVISORIES.

POTENTIAL IMPACTS OVER THE WEEKEND...MAINLY SUN INTO MON...WOULD BE
HEAVY RAINFALL...COASTAL FLOODING...AND HIGH WINDS. ADDITIONAL
IMPACTS FROM THIS SYSTEM COULD BE SIGNIFICANT BEACH EROSION AND
DANGEROUS RIP CURRENTS.
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Florida officially out of the cone of confusion.

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Quoting presslord:
That is hilarious, but a sad telling commentary on our times, LOL.
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Quoting biff4ugo:
How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?

Forgive me if i am wrong but i was thinking storm surge would just go around the island, as there is no big land masses to back up the surge. The surge would only get to a certain level which might only be a few feet above the normal tidal level. I am happy to be corrected.
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Quoting synthvol:
For anyone who is NOT prepared or ready to evacuate in the cone. Hurricane Ike ('08) was "only" a Cat II storm, but had a large windfield like Irene.



Good luck and God bless anyone in the path of this one, and we are praying it curves straight back out into the Atlantic (and misses Bermuda!!!)
This guy was prepared!! See it didn't affect him at all! Must be one of the "smart" ones.
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The reason why Irene is moving so slow is she is fighting between the weakness to the NW and the deep layer low level flow it's currently in right now. Opposing steering currents= slow movement. Either the high to the north will take over or the shortwave approaching will be of significant amplitude to start exerting a NWward pull on her. Only two options I see right now. Couple that with model support, we're more than likely to start seeing more and more of a NW motion as opposed to WNW. But as many on here have said, nothing in weather is written in stone. It's watch and see now.
Member Since: December 18, 2006 Posts: 7 Comments: 2685
Quoting Drakoen:
Good morning everyone. I see that the models have converged onto a solution taking Irene east of Florida and possibly have her impacting the Carolinas. Water vapor imagery shows a strong trough of low pressure off the eastern seaboard that should help pull Irene more towards the northwest with time. Water vapor imagery also shows a shortwave trough over the northern Plains region and this will be the first of the series of shortwaves to help keep the weakness alive for Irene to follow through. 12z upper air data shows that the 500mb heights have dropped from 594dm over Bermuda to 589dm a sure sign that the ridge to the north is weakening. The key to where Irene will eventually end up in the Mid-Atlantic will initially be where it decides to make the turn to the northwest as the trough to the west and the ridge to the east will buckle her in possibly along the eastern seaboard from the Mid-Alantic towards New England.


Ok dude...this time I'm not jokin'....Ya think we're good?
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This storm look like it's 80-90 mph hurricane for now...
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1167. Skyepony (Mod)
Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 23rd day of the month at 15:06Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Storm Number & Year: 09L in 2011
Storm Name: Irene (flight in the North Atlantic basin)
Mission Number: 8
Observation Number: 05
A. Time of Center Fix: 23rd day of the month at 14:38:20Z
B. Center Fix Coordinates: 20°31'N 70°57'W (20.5167N 70.95W)
B. Center Fix Location: 66 miles (107 km) to the S (170°) from Cockburn Town, Turks and Caicos Islands (GBR).
C. Minimum Height at Standard Level: 2,918m (9,573ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 62kts (~ 71.3mph)
E. Location of the Estimated Maximum Surface Wind: 11 nautical miles (13 statute miles) to the E (92°) of center fix
F. Maximum Flight Level Wind Inbound: From 193° at 67kts (From the SSW at ~ 77.1mph)
G. Location of Maximum Flight Level Wind Inbound: 13 nautical miles (15 statute miles) to the E (98°) of center fix
H. Minimum Sea Level Pressure: 980mb (28.94 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 9°C (48°F) at a pressure alt. of 3,040m (9,974ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 14°C (57°F) at a pressure alt. of 3,107m (10,194ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 11°C (52°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Open in the southwest
M. Eye Shape & Diameter: Circular with a diameter of 25 nautical miles (29 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 2 nautical miles
Remarks Section - Remarks That Were Decoded...
Maximum Flight Level Wind: 67kts (~ 77.1mph) in the east quadrant at 14:34:30Z
Maximum Flight Level Wind Outbound: 68kts (~ 78.3mph) in the northwest quadrant at 14:44:00Z
Remarks Section - Additional Remarks...
SFC CTR NOT VISIBLE
BKN CLOUDS BLO

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Quoting rkay1:
When people say FISH STORM, I believe they are referring to it missing CONUS.  Stop acting all moral and get off your high horses.  Go pray for the kids in Haiti.  BTW, it is looking more and more like it will miss the CONUS.

It's already been established that Irene is not a fish. So far, it has already impacted Puerto Rico, Dominican Republic, and Haiti.

From what I can deduce from the wealth of informative bloggers is that CONUS is NOT out of the woods, YET.

You have every right to your opinion, just don't get your knickers in a wad when someone disagrees with you.
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1165. 7544
Quoting Nolehead:
looks like it might hit just a tad to the south of the next nhc mark...just dont see that big turn happening anytime soon...but it's just me..


agree espeacialy if the dry air and now some shear getting close to her will bring a down a notch things could change fast as u see now no cat 4 for bahamas down to a 3 wait for the next 12 hours to see what happens
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Quoting 7544:
dry air getting to her now may go down to 90mph soon imo


Yep that island is a good thing. And luckily Haiti was spared mostly this time.

Will take a while to reestablish the core.
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that blob off jax looks like its starting to orgaize,man that would be a HUGE fly in the ôntment and if it develops throw all the models out and start over,it would be unpresidented,it sure looks highly suspect on high res loop from cod
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Quoting SPLbeater:


Hispaniola is disrupting her southenr outflow, some dry air is being sucked into Irene, and therefore she isnt strengthening any atm


I know, my comment was sarcastic lol. It won't strengthen until it gets away from Hispaniola.
Member Since: August 10, 2010 Posts: 2 Comments: 1970
Quoting MyrtleCanes:


Is anyone considering that that higher terrain of the dominican may temporarily weaken her a hair and cause a westward drift today influencing the long term track a little westward. I think the east shifts may have plateaued or stopped and west tweaks may start, we'll see.

I still favor a Hazel/Bertha hybrid track and approach to NC/SC
thats why nhc has not discounted the gfdl until just recently
Member Since: September 11, 2010 Posts: 0 Comments: 4015
My only moderately educated guess is that the collapsing thunderstorms is being caused by dry air coming in that is being brought in from the south, which has to come down the mountains of Hispanola and drys out as it does.
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Quoting biff4ugo:
How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you know something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?

Does the cone include the width of the storm or just uncertainty about the path of the eye?

Go to the kitchen and get a plate and a bowl.

Fill them with water.

Blow on them.

Which one is easier to displace the water out of??

There you go.
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1158. BA
Quoting Patrap:
Storm Relative 1km Geostationary Visible Imagery




looks like a real hurricane (unlike other storms this year so far) :)
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Quoting biff4ugo:
How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?


The slope of the continental shelf allows for the water to pile up as the storm approaches land.
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11am advisory = big relief for S. Florida
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Quoting NICycloneChaser:


Because it hasn't strengthened? I'm just guessing...


Hispaniola is disrupting her southenr outflow, some dry air is being sucked into Irene, and therefore she isnt strengthening any atm
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Quoting interstatelover7165:
Why isn't the NHC upgrading Irene's strength at all?


They didn't because it isn't. They would if it was, but it's not, so they won't... at this time.

Probably will. Later. If it does.
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Hope this is turning into a fish storm
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I do not know about you all but 98L is taking forever to move anywhere. I think I have seen this system in this area for about a week now.

Link
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1150. Drakoen
Good morning everyone. I see that the models have converged onto a solution taking Irene east of Florida and possibly have her impacting the Carolinas. Water vapor imagery shows a strong trough of low pressure off the eastern seaboard that should help pull Irene more towards the northwest with time. Water vapor imagery also shows a shortwave trough over the northern Plains region and this will be the first of the series of shortwaves to help keep the weakness alive for Irene to follow through. 12z upper air data shows that the 500mb heights have dropped from 594dm over Bermuda to 589dm a sure sign that the ridge to the north is weakening. The key to where Irene will eventually end up in the Mid-Atlantic will initially be where it decides to make the turn to the northwest as the trough to the west and the ridge to the east will buckle her in possibly along the eastern seaboard from the Mid-Alantic towards New England.
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Quoting osuwxguynew:
Looks like Irene just sucked in another gulp of warm, dry air descending from the higher terrain of the Dominican Republic. Inner core will suffer for a bit, but she should RI later this afternoon or evening as she finally pulls away DRs influence.


Is anyone considering that that higher terrain of the dominican may temporarily weaken her a hair and cause a westward drift today influencing the long term track a little westward. I think the east shifts may have plateaued or stopped and west tweaks may start, we'll see.

I still favor a Hazel/Bertha hybrid track and approach to NC/SC
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Quoting biff4ugo:
How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?


Pretty good link on storm surge:

Link
Member Since: December 18, 2006 Posts: 7 Comments: 2685
looks like it might hit just a tad to the south of the next nhc mark...just dont see that big turn happening anytime soon...but it's just me..
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1145. 7544
dry air getting to her now may go down to 90mph soon imo
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How does shallow water allow for larger storm surges?
Shallow water moves less due to increased bottom friction, unless you know something I am missing.
It may be more damaging in shallow areas because the coast isn't prepared for waves of any size.
Yes?

Does the cone include the width of the storm or just uncertainty about the path of the eye?
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Quoting CaneHunter031472:
My prayers are with all the people in the Bahamas and North Carolina. Be Ready because unfortunately this is almost for sure going to hit you. Florida count your blessings we are not in the peak of this season yet.


I don't think its going to hit them... everything is slowly shirting it east... It may run close up the coast.. but not a direct hit.
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1141. scCane
Quoting Patrap:
I count 7 outflow boundaries racing NW and west.

Hispaniola must be doing a number on it and it's slow speed isn't helping.
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Quoting Waltanater:
Why do you keep posting the same image over and over? Once is enough, unless it changes drastically.


Just because you are reading all of the posts does not mean that others who can only check in once and a while can go back hundreds of posts to see whats going on.

Especially for those of us who sometimes can only use our phones to see what is going on.

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1138. maeko
Quoting charlottefl:


If she weakened a lot, it would only drive her slightly further west..


hmmm, Do Not Want
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Quoting NSgirl:
Good morning folks, my name is Connie, I live in Nova Scotia, Canada......wondering what's the likelyhood we'll get some effects from Irene up here????




good morning to you. too early to tell. just keep checking in or your local weather service should keep you updated. how is the weather now? fall already arriving?
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did it jut wobble west? looks like interaction with land may have caused it to?
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back to the discussion:

ok so the latest models are trending eastward which would be good news for South Carolina and much of North Carolina too. However, I take this light since it raises the flag for me and some here already said they trend eastward during the mourning and the westward in the evening. So I wait till evening to see what happens.

Here is a look over nearly the past 24 hours

11 AM Monday AUG 22

Photobucket

11 PM Monday AUG 22
Photobucket

8 AM Tuesday AUG 23
Photobucket
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About JeffMasters

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