Leslie headed towards Bermuda; Tropical Storm Michael forms

By: Dr. Jeff Masters , 3:01 PM GMT on September 04, 2012

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Tropical Storm Leslie continues to suffer from moderately high wind shear of 15 - 20 knots, due to strong upper-level winds out of the northwest. The shear is keeping heavy thunderstorms confined to the southeast quadrant of the storm. Satellite loops show that Leslie has almost no heavy thunderstorm activity near its center, and the storm is crawling north at walking pace, 3 mph. Leslie's slow forward speed means that the storm is staying over the cold water stirred up by the storm's winds, inhibiting intensification. According to the latest SHIPS model forecast, the shear is expected to stay moderately high through Tuesday night, then drop to the low category, 5 - 10 knots, by Thursday afternoon. At that time, Leslie will be over warm ocean waters of 29 - 30°C, and the reduction in shear and warm waters should aid intensification. However, Leslie's motion will continue to be slow, keeping the storm over its cool water wake, and keeping any intensification slow. Once Leslie begins moving more quickly on Saturday, this effect will diminish, and Leslie could be at Category 2 strength on Sunday morning, as indicated in the official NHC forecast. Steering currents for Leslie are expected to be weak through Friday, as Leslie is stuck between two upper level lows. The latest guidance from our top computer models continues to show Leslie making a very close pass by Bermuda on Saturday. Leslie is a huge storm, and tropical storm-force winds are expected to extend outward from its center 250 miles by Friday. Bermuda is likely to see a 48-hour period of tropical storm-force winds beginning Friday night that lasts until Sunday night. The official NHC forecast shows Leslie nearly making a direct hit on Bermuda, but the uncertainty in 4-day NHC forecasts is around 200 miles. Thus, the latest 11 am EDT NHC wind probability forecast calls for just a 12% chance of hurricane force winds on Bermuda on Saturday. Nevertheless, Leslie is capable of bringing an extended period of hurricane-force winds lasting six or more hours to Bermuda Saturday night through Sunday morning, should a direct hit materialize.


Figure 1. Morning satellite image of Tropical Storm Leslie. The low-level circulation center has very little in the way of heavy thunderstorms surrounding it, thanks to strong northwest winds creating 15 - 20 knots of wind shear.

Leslie will stay stuck in a weak steering current environment until a strong trough of low pressure approaches the U.S. East Coast on Saturday. This trough should be strong enough to pull Leslie quickly to the north on Saturday and Sunday, and Leslie may be close enough to the coast that the storm will make landfall in Nova Scotia or Newfoundland, Canada on Monday, September 10. None of the reliable models have shown that a direct hit on New England will occur, but we can't rule that possibility out yet. The storm may also miss land entirely, and brush by the coasts of Nova Scotia and Newfoundland. Large swells from Leslie reached Cape Hatteras, North Carolina last night, and will begin pounding the entire Eastern Seaboard today through Sunday. These waves will be capable of causing significant beach erosion and dangerous rip currents. The Hurricane Hunters are scheduled to make their first flight into Leslie on Wednesday afternoon.


Figure 2. Morning satellite image of Tropical Storm Michael.

Tropical Storm Michael forms in the Central Atlantic
Tropical Storm Michael has formed in the Central Atlantic on Monday, but is not destined for fame. Satellite loops show that this is a very small tropical cyclone, and the storm is well away from any land areas. Michael is under moderately high shear of 15 - 20 knots, and this shear is forecast to remain at 15 - 20 knots through Wednesday. Since Michael is such a small storm, just a modest increase in shear could destroy it. But if Michael survives until Thursday, when shear is expected to fall to the low range, it has the opportunity to strengthen.

Michaels's formation on September 4 puts 2012 in third place for earliest formation date of the season's thirteenth storm. The record is held jointly by 2005, which had Hurricane Maria form on September 2, and 2011, which had Tropical Storm Lee form on September 2 (there was an unnamed tropical storm that year before Lee.) None of the models show that Michael will threaten any land areas. Michael is a classic example of the type of storm that likely would have been missed before the advent of satellites, since the storm is small, far from land, and may be short-lived.

Jeff Masters

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Quoting DocNDswamp:


Perhaps I read that too quickly... as I was gonna ask - Why, was it your deciding vote or missing chad that put him in office in 2000?
;)


It was a hanging chad.
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Quoting keithneese:


LOL. This reminds me of the time my son asked me if the world was still black and white when I was his age.
I remember the huge hype over something new coming out..imagine..color tv?
Member Since: August 6, 2011 Posts: 4 Comments: 33230
Quoting LargoFl:
someone asked about steering currents in the gulf..........

wow
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Quoting leftlink:
Here are the other two slides describing the "Modified Saffir Simpson" idea.





So this is like the current scale except that a "strong tropical storm" category is added (suggested by Aussieweather), a category 6 is added, the categories are more uniformly spaced for wind, and most importantly, CONDITIONS LIKE EXTREMELY HIGH FLIGHT LEVEL WINDS, HIGH OVERALL STORM AREA/KINETIC ENERGY, AND ALSO RAPID PRESSURE DROPS will result in the storm's classification getting "bumped up" to a higher level.


It will take some refinement and work to be able to calculate things like total kinetic energy in real time, but I think it's a good start. BTW, the NHC is not going to like this idea. From Wikipedia:

"In 2009, the NHC made moves to eliminate pressure and storm surge ranges from the categories, transforming it into a pure wind scale, called the Simpson Hurricane Wind Scale (Experimental) [SSHWS].[5] The new scale became operational on May 15, 2010.[6] The scale excludes flood ranges, storm surge estimations, rainfall, and location, which means a Category 2 hurricane which hits a major city will likely do far more cumulative damage than a Category 5 hurricane that hits a rural area.[7] The agency cited various hurricanes as reasons for removing the "scientifically inaccurate" information, including Hurricane Katrina (2005) and Hurricane Ike (2008), which both had stronger than estimated storm surges, and Hurricane Charley (2004), which had weaker than estimated storm surge.[8]"

http://en.wikipedia.org/wiki/Saffir%E2%80%93Simps on_Hurricane_Scale
Member Since: October 2, 2004 Posts: 0 Comments: 9651
Quoting LargoFl:
72 hours we got a Low in the gulf

Is anyone talking about it??? NHC, TWC?
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someone asked about steering currents in the gulf..........
Member Since: August 6, 2011 Posts: 4 Comments: 33230
Quoting jascott1967:


I'm too old to pay attention. I'm so old my memory is in black and white, just like rainbows when you were a kid.


LOL. This reminds me of the time my son asked me if the world was still black and white when I was his age.
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Quoting TropicalAnalystwx13:
BULLETIN
TROPICAL STORM LESLIE ADVISORY NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
500 PM AST TUE SEP 04 2012

...LESLIE BECOMING A LITTLE BETTER ORGANIZED AS IT MOVES SLOWLY
NORTHWARD...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...25.3N 62.6W
ABOUT 500 MI...805 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.35 INCHES

hmmm.....
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Quoting TropicalAnalystwx13:

Katrina was a Category 4 with 145 mph winds (IIRC) at its first landfall. Andrew had winds in excess of 160 mph.

hmmm....
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BULLETIN
TROPICAL STORM LESLIE ADVISORY NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
500 PM AST TUE SEP 04 2012

...LESLIE BECOMING A LITTLE BETTER ORGANIZED AS IT MOVES SLOWLY
NORTHWARD...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...25.3N 62.6W
ABOUT 500 MI...805 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...994 MB...29.35 INCHES
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Quoting TomballTXPride:
I thought AGW initially meant more storms. Then I remember recently it's been changed to reflect fewer storms but stronger ones?? Where have all the majors been this year. Okay now I'm confused!!!!!!!!


It appears that the warmer water may result in storms that would have been sheared to death surviving... as storms with a larger diameter circulation. Anyone else see this pattern?
Member Since: December 28, 2010 Posts: 0 Comments: 134
72 hours we got a Low in the gulf
Member Since: August 6, 2011 Posts: 4 Comments: 33230
Quoting GTcooliebai:
96 hrs. 4 systems:


nadine and oscar?
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Quoting RTSplayer:


Doesn't do enough.

Andrew and Katrina landfalls were nearly identical air pressures, yet it's obvious Katrina was far more powerful over all.

Katrina was a Category 4 with 145 mph winds (IIRC) at its first landfall. Andrew had winds in excess of 160 mph.
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Quoting RitaEvac:
swirly thing in central gulf has hot air around it, notice the black around it




hmmm....
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96 hrs. 4 systems:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
swirly thing in central gulf has hot air around it, notice the black around it



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Quoting RTSplayer:


Doesn't do enough.

Andrew and Katrina landfalls were nearly identical air pressures, yet it's obvious Katrina was far more powerful over all.


Did you just say that Katrina was more powerful than Andrew?? You can't be serious..
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Quoting RTSplayer:


Doesn't do enough.

Andrew and Katrina landfalls were nearly identical air pressures, yet it's obvious Katrina was far more powerful over all.


Not only that, but Andrew was a relatively small, fast mover, and Katrina was a huge, slow mover. Central pressure is just one small part of the puzzle.
Member Since: October 2, 2004 Posts: 0 Comments: 9651
368. auburn (Mod)
Quoting mcluvincane:
Euro developing isaac remnants at 72 Hrs in central gulf lol


Isaac Jr...
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Quoting MahFL:


That picture could have been taken years ago.


No, it was taken today.
http://www.fox10tv.com/dpp/news/local_news/baldwi n_county/crews-cleaning-organic-masses

It appears that the substance is not oil but "organic" matter. There's a lot of kelp and seaweed in the Gulf that gets formed into mats by storms. It looks nasty when it gets washed up (I've seen it before) but it's just part of the normal flora in the Gulf.

Edit: BTW, BP crews are out there cleaning up the seaweed now. BP will be cleaning up anything that looks remotely like oil for about the next 30 years. Should help the unemployment rate down this way. :)
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Quoting ILwthrfan:


What would be the draw back of just re-adjusting the Saffron Simpson Hurricane scale based on air pressure rather than average wind speed?


Doesn't do enough.

Andrew and Katrina landfalls were nearly identical air pressures, yet it's obvious Katrina was far more powerful over all.
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Here are the other two slides describing the "Modified Saffir Simpson" idea.





So this is like the current scale except that a "strong tropical storm" category is added (suggested by Aussieweather), a category 6 is added, the categories are more uniformly spaced for wind, and most importantly, CONDITIONS LIKE EXTREMELY HIGH FLIGHT LEVEL WINDS, HIGH OVERALL STORM AREA/KINETIC ENERGY, AND ALSO RAPID PRESSURE DROPS will result in the storm's classification getting "bumped up" to a higher level.

Note that the "figure 3" I posted earlier is not needed to do the calculation -- it just shows example intensity values.
Member Since: December 28, 2010 Posts: 0 Comments: 134
Euro developing isaac remnants at 72 Hrs in central gulf lol
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Quoting Grothar:


Pre-blob! Pay attention.


I'm too old to pay attention. I'm so old my memory is in black and white, just like rainbows when you were a kid.
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Quoting GTcooliebai:
What is that in the south central gulf?
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Quoting wxchaser97:

The consistency in forecasting a storm is there and we wouldn't know a final landfall until a storm even formed.


That's nice. Using my stock market analogy, with no expensive models, I can confidently predict the market close will be different 16 days from now than what it is today. That gives me absolutely no useful information, but I know my model is going to be right. The GFS at 384 hours can tells us a storm (might) form (somewhere) and then (may) take (one of many paths) to someplace. It's about as good as my stock market model. :)
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215 MississippiWx:
Bad news. (Possible) Oil has resurfaced thanks to Isaac. This picture is from an Alabama beach

Could be "better" news than one might imagine.
Those in the know were saying that sufficiently strong hurricane surges could flush the DeepwaterHorizon non-volatile (kerosene and heavier) oil-remnants out of the bayous.
Not so nice for beach goers, but better for the wildlife and fisheries in the long run.
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359. MahFL
Quoting MississippiWx:
Bad news. (Possible) Oil has resurfaced thanks to Isaac. This picture is from an Alabama beach.



That picture could have been taken years ago.
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Quoting RTSplayer:
Here's an easy system.

1, Start with 1015mb.

2, Find the approximate area covered by each full Millibar of pressure in square kilometers, but not overlapping stronger(lower) pressure values. i.e. the area of each amorphous "donut" of pressure lines around the CoC.

3, For each partition, subtract forecasted landfall intensity in pressure from 1015.

4, Square the result of the pressure subtraction for each partition and multiply by that partition's size.

5, Add all of the partitions.


I like the concept here... you are calculating the "summation" of the pressure differential from normal, right? Only concern I have is that it might take quite a bit of work to do the calculation just for one storm... though I guess that it could be automated by a computer, right?

I have been trying to approximate hurricane strength with a really simple calculation, thinking that the simpler the better because if locals can perform the calculation on their own they are more likely to trust the NHC. Here is a draft of a table for "Size and Wind Field Power Factor":



The number here is just the radius of trop. storm winds added to the radius of hurricane winds, and then you take that and multiply by the max wind speed. I am calling this the SWPF (Size and Wind Field Power Factor).

It would be interesting to see how the SWPF measurement stacks up in recent storms as compared to your scheme... whether it captures the essence of the storms overall danger for surge, duration, etc. or whether the two schemes are way off.

Take a look:

Link



Member Since: December 28, 2010 Posts: 0 Comments: 134
Note the difference in the distances travelled by Leslie on its 4th and 5th day as a TropicalStorm.
4th day: 204miles(329kilometres) @ ~8.5mph(13.7km/h)
5th day : 88miles (141kilometres) @ ~3.7mph ( 5.9km/h)
All times in GMT
Derived from NHC_ATCF data for TropicalStormLeslie at 2Sept.6pm
KXFL-PalmCoast :: BDA-Bermuda

The longer kinked line traces Leslie's path on its 4th day as a TropicalStorm
The shorter kinked line traces Leslie's path on its 5th day as a TropicalStorm
The southernmost dot on the longest straight line is TS.Leslie's most recently reported position

The longest line is a straightline projection through TS.Leslie's 2 most recent positions to it's closest approach to Bermuda
3Sept.12pm: TS.Leslie had been headed for passage over OrmondBeach (right,KXFLblob)
3Sept.06pm: TS.Leslie had been headed for passage 133miles(214kilometres)WSWest of Bermuda
4Sept.12am: TS.Leslie had been headed for passage 276miles(443kilometres)ESEast of Bermuda
4Sept.06am: TS.Leslie had been headed for passage 340miles(548kilometres)ESEast of Bermuda
4Sept.12pm: TS.Leslie was heading for passage 126miles(202kilometres)East of Bermuda
4Sept.06pm: TS.Leslie had been headed for passage16miles(26kilometres)WSWest of Bermuda

Copy&paste kxfl-29.404n81.094w, 31.431n66.919w, 31.196n60.17w, 30.299n59.418w, 32.387n62.5w, 32.281n64.887w-bda-32.368n64.647w, 21.3n60.9w- 22.1n61.4w- 22.8n61.6w- 23.4n62.2w- 23.6n62.7w, 23.6n62.7w- 23.8n62.8w- 24.1n62.7w- 24.5n62.5w- 24.8n62.5w, 24.8n62.5w-25.1n62.6w, 24.8n62.5w-32.209n65.147w, 32.281n64.887w-32.209n65.147w into the GreatCircleMapper for a larger map and other information
The previous mapping for comparison
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<
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Quoting Grothar:


You're too young to remember that one.


Actually the 1967 in my name isn't Anno Domini, rather BC.
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Quoting Skyepony:


I went back & inserted a two day movie so everyone can see it come down from IL/IN. Judging by that & watching the evolution in the models it's only going to be about 1/3 of Isaac the trough that is beginning to interact with it.

Hope you dry out a little.


Thank you, Skye. It does look like what I've been saying for the last three days. Something that's not obvious tore the Isaac remnant low in two and intensified the part over southern IL/IN and sent it south with enough energy to cause heavy rains, flash floods, and a few isolated tornadoes. The jet stream looks like it should have picked the whole thing up and sent it east. It's pretty clear we don't even understand micro level meteorology too well yet.
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48 hrs.

Member Since: August 31, 2009 Posts: 0 Comments: 5628



Tropical Storm MICHAEL
...TROPICAL STORM MICHAEL FORMS IN THE EASTERN ATLANTIC... ...MICHAEL POSES NO THREAT TO LAND...
11:00 AM AST Tue Sep 4
Location: 27.0N 43.5W
Moving: NNW at 5 mph
Min pressure: 1006 mb
Max sustained: 40 mph
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Quoting MAweatherboy1:

The GFS has been consistently showing this storm, but it's been all over the place with possible landfall locations.

18z yesterday had South Florida:



0z last night had a western Gulf (probably Mexico) storm:



6z this morning had a Bermuda storm:



12z had twins, with one hugging the East Coast:


The consistency in forecasting a storm is there and we wouldn't know a final landfall until a storm even formed.
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Quoting jascott1967:


An African blob?


Pre-blob! Pay attention.
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Quoting Doppler22:

Do u have an expanded view that includes Michael?


sorry..that version only has north america
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Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting jascott1967:


Spin you right around.

Caught between two spins, feelin' like a fool.

Two can be as bad as one
it's the lonliest number since the number one


You're too young to remember that one.
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Quoting GetReal:


Get Real! :)
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Tropical Cyclone Information Statements

WOCN31 CWHX 041745
Tropical cyclone information statement issued by the Canadian
Hurricane Centre of Environment Canada at 1:01 PM ADT Tuesday
4 September 2012.
------------------------------------------------- --------------------
Tropical cyclone information statement for:
=new= Atlantic provinces.

For tropical storm Leslie.

The next statement will be issued by 3:00 PM ADT Wednesday.

Early discussion regarding tropical storm Leslie and possible
Influence in Eastern Canada.

------------------------------------------------- --------------------
==discussion==
The Canadian Hurricane Centre will be monitoring the development of
tropical storm Leslie this week. The storm is expected to move very
slowly and intensify gradually over the next several days.
Computer models are predicting Leslie to only travel 500 kilometres
in 4 days which is basically a person's average speed of walking.
With such a slow speed of travel and the fact that the storm is still
in its organizing stage, there is much (more than usual) uncertainty
in the predicted path/intensity over the next week.

Computer models indicate that Leslie could eventually push through
the large 'Bermuda high' and acellerate toward Eastern Canada with a
range of track scenarios from Maine to offshore Newfoundland.
The middle of these track forecasts is over Newfoundland - but even
that 'average' will likely shift by hundreds of kilometers over time
with each new run of simulations. If Leslie makes it to Eastern
Canada, it would not likely do so until early next week.

We will update this bulletin throughout the week if Leslie continues
to develop and will provide interpretation of the possible scenarios
and degree of predictability.

Visit WWW.WEATHEROFFICE.GC.CA/HURRICANE/TRACK_E.HTML (all in lower
case) for the latest hurricane track map.

END/FOGARTY


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Quoting Tropicsweatherpr:


Hi Gro. Is raining in parts of the Saharan Dessert and those two are going to be the next Cyclones in North Atlantic.


I think so. I wrote it in my blog early this morning. Below average season, HUH. LOL
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Quoting LargoFl:
geez im caught between two spins lol


Spin you right around.

Caught between two spins, feelin' like a fool.

Two can be as bad as one
it's the lonliest number since the number one
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The models bounce all over the place until there is something to latch on to. They sense them upcoming activity now. Leslie is still the big story.
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Good afternoon everyone, school was really good today. Anyway I see Micheal has formed and not much is going on with Leslie. I just saws the 12z GFS, that wouldn't be good for the US. The Wxchaser97 Forecast Model is running right now.
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Quoting sar2401:


Yeah, I know, but I'm just slightly younger than Gro. I think I'll be pushing up daisies long before we get a reliable 384 hour model.


slightly younger?

So how was the Big Bang?
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337. VR46L
Quoting MAweatherboy1:

The GFS has been consistently showing this storm, but it's been all over the place with possible landfall locations.

18z yesterday had South Florida:



0z last night had a western Gulf (probably Mexico) storm:



6z this morning had a Bermuda storm:



12z had twins, with one hugging the East Coast:



Remind you of a certain storm called Isaac, first couple of days ,It appeared it was the north east storm of DOOM ,then it was Florida wipe out DOOM for a few days, then it was Houston DOOM ,then it switched back to Florida DOOM ,until it finally moved west to DOOM Panhandle a couple of days, and finally it was NOLA.
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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.