TD 13 intensifying; Katia may pass uncomfortably close to U.S.

By: Dr. Jeff Masters , 3:28 PM GMT on September 02, 2011

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Tropical Depression Thirteen formed last night over the Northern Gulf of Mexico and is slowly intensifying, but isn't in a hurry to go anywhere. What TD 13 will do is dump torrential rains along the northern Gulf Coast over the next three or more days. So far, rain amounts along the coast have mostly been below one inch. At New Orleans Lakefront Airport, just 0.32" inches of rain had fallen from TD 13 as of 10 am CDT. Some coastal regions have received up to two inches, according to radar rainfall estimates. TD 13 is generating a large area of 30 - 35 mph winds over the Gulf of Mexico. At 7:20 am CDT, winds at the Mississippi Canyon 711 oil rig were southeast at 47 mph. This is above tropical storm force, but the wind instrument was 348 feet (106 m) above the ocean surface, and winds near the surface were probably considerably lower, near 35 mph. Latest surface wind observations from an Air Force hurricane hunter aircraft support leaving TD 13 as a tropical depression. Long range radar out of Mobile, Alabama shows heavy rain showers building along the northern Gulf Coast, but these rain showers are not well-organized into spiral bands. Strong upper-level winds out of the west-northwest are creating a moderate 10 - 20 knots of wind shear over TD 13, keeping the storm's heavy thunderstorms disorganized and pushed to the east side of the storm. However, latest satelllite loops show TD 13 is becoming increasingly organized, with a respectable spiral band forming on the southeast side, and an increase and areal coverage of heavy thunderstorm activity. This is very likely to be a tropical storm later today.


Figure 1. Radar-estimated rainfall from TD 13 from the New Orleans radar.


Figure 2. U.S. drought conditions on August 30. The rains from TD 13 have the potential to bring major drought relief to drought-stricken portions of the coast. Note how Eastern North Carolina is no longer in drought, thanks to the rains from Hurricane Irene. These rains also came close to putting out a persistent fire that had been burning in the Great Dismal Swamp near the Virginia/North Carolina border. Image Credit: U.S. Drought Monitor.

Forecast for TD 13
TD 13's large size, ill-formed circulation center, and the presence of dry air on its west side due to an upper-level trough of low pressure argue against rapid intensification of the storm for the next three days. Also tending to slow intensification will be the slow movement of the storm, which will allow cold water from the depths to rise to the surface, thanks to wind and wave action. Tropical cyclones strongly cool the water's surface when they pass over it, as seen in the time vs. depth chart of sea surface temperatures during Hurricane Irene's passage along the New Jersey coast (Figure 3.) However, the Gulf of Mexico has some very warm waters near TD 13 that extend to great depth (Figure 4), so the surface cooling imparted by TD 13 will be less than that seen for Hurricane Irene. As TD 13 moves closer to the coast, more and more of its circulation will be over land, which will also slow intensification. NHC's 11 am EDT wind probability forecast for TD 13 gave the storm a 23% chance of intensifying into a hurricane by Sunday. Assuming TD 13 does not attain hurricane strength, wind damage and storm surge damage will likely not be the main concern--fresh water flooding from heavy rains will be the most dangerous impact. Also of concern is the possibility of tornadoes. NOAA's Storm Prediction Center is currently not highlighting the Gulf Coast in their "slight risk" area for severe weather, due to the lack of enough solar heating to create instability. However, there will be plenty of wind shear in the lower part of the atmosphere that can potentially create spin in the coastal thunderstorms, and it is possible that as TD 13 intensifies, it may be able to generate several dozen tornadoes.

Coastal Louisiana, Mississippi, Alabama, and the extreme western Panhandle of Florida will likely receive very heavy flooding rains that will intensify Saturday and peak on Sunday. These rains should be able to put out the stubborn marsh fire east of New Orleans that has brought several days of air quality alerts to the city, but may cause moderate to severe flooding problems in other areas. The latest rainfall forecast from NOAA Hydrological Prediction Center shows that a large area of 15+ inches of rain is expected over Southeast Louisiana and coastal Mississippi. The region is under moderate drought, so flooding problems will be delayed compared to what we'd normally expect from heavy rains of over a foot. Flash flood watches are posted for New Orleans and surrounding areas, and rainfall amounts of 1 - 3 inches per hour are possible in some of the heavier rain squalls. Ocean temperatures are near record warmth, 88°F (31°C), which will provide plenty of moisture for heavy rains, and plenty of energy to help TD 13 strengthen into a strong tropical storm. Steering currents will be weak in the Gulf this weekend and early next week, which will likely make the motion of TD 13 erratic at times.


Figure 3. EPA, in conjunction with Rutgers University and the NJ Department of Environmental Protection, has an Autonomous Underwater Vehicle (AUV, aka the Glider) deployed off the coast of NJ (since early August) continuously monitoring ocean temperature, density, salinity, sound velocity and dissolved oxygen at different depths. The AUV's path and data are displayed at the following website: http://marine.rutgers.edu/cool/auvs/index.php?did =221&view=imagery. The plot of temperature versus time above shows that in the weeks prior to the arrival of Irene, the ocean was heavily stratified, with warm waters of 24 - 26°C (75 - 79°F, red colors) extending from the surface to a depth of 10 - 15 meters. A sharp thermocline existed at a depth of about 15 meters, and ocean temperatures were colder than 14°C (57°F, dark blue colors) below the thermocline. The strong winds and high wave action of Hurricane Irene on August 28 - 29 stirred up cold water from the depths to the surface, cooling the surface waters to 17 - 19°C (63 - 67°F). In the days since the hurricane, surface waters have begun to warm again. Thanks go to Kevin Kubik, Deputy Director of the Division of Environmental Science and Assessment for EPA Region 2, for making me aware of this data.


Figure 4. The total amount of heat energy in the ocean available to fuel a tropical cyclone, in kilojoules per square centimeter of surface area. Tropical cyclones that move over ocean areas with TCHP values in excess of 70 - 90 kJ/cm^2 commonly undergo rapid intensification. Waters that are warm to a great depth have the highest TCHP, and the Loop Current that brings warm water northwards from the Caribbean to the Gulf of Mexico usually has the highest TCHP values in the Atlantic. Currently, we have an eddy that broke off from the Loop Current earlier this summer, now located a few hundred miles south of the Louisiana coast, that also has high TCHP values. Image Credit: NOAA/AOML.

Hurricane Katia
Hurricane Katia is continuing its long trek across the Atlantic Ocean today, and will not pose a danger to any land areas over the next five days. Katia is still struggling with dry air and moderate wind shear of 10 - 20 knots. Latest satellite loops show surface-based arc-shaped clouds racing to the southwest away from Katia's core, a sign that dry air is penetrating into Katia's thunderstorms and creating strong downdrafts that are robbing the storm of heat and moisture. Katia is over warm ocean waters of 28.5°C, and these waters will increase in temperature to 29°C over the next five days. Katia will pass well north of the region of cooler waters stirred up by the passage of Hurricane Irene last week.

The models are split on when the upper-level trough of low pressure bringing the wind shear to Katia will move away, and the storm may spend two more days battling wind shear and dry air before the upper-level trough pulls away to the north and allows Katia to intensify more readily. It is still unclear how much of a threat Katia may pose to the U.S., but it is becoming increasingly clear that Katia will pass uncomfortably close to the U.S. East Coast. The trough of low pressure currently steering Katia to the northwest will lift out early next week, and a ridge of high pressure is expected to build in, forcing Katia more to the west. This decreases the danger to Bermuda, but increases the danger to the U.S. A second trough of low pressure is expected to begin affecting Katia by the middle of next week, and will potentially recurve the storm out to sea before it hits the U.S. However, the models differ widely on the strength and timing of this trough. Meteorologist Grant Elliot of Australia's Bureau of Meteorology in Perth pointed out to me yesterday that the long-range forecast for Katia has more than the usual amount of uncertainty, due to the inability of the computer models to agree on what will happen to Tropical Storm Talas in the Western Pacific. Talas is expected to hit Japan early on Saturday as a strong tropical storm, then race northwestwards into the Bering Sea off the coast of Alaska. Talas is then expected to transition into a powerful extratropical storm in the waters south of Alaska. This storm will create a ripple effect downstream in the jet stream, all the way to North America, by early next week. The timing and amplitude of the trough of low pressure off the U.S. East Coast expected to potentially recurve Katia out to sea next week is highly dependent upon the strength of Tropical Storm Talas during its transition to an extratropical storm. The computer models are not very good at handling these sorts of transitions, leading to more than the usual amount of uncertainty in the long-range outlook for Katia. It will probably be another 2 - 3 days before the models will begin to converge on a solution for the long-term fate of Katia. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have a 17% chance of hitting North Carolina, a 21% chance of hitting Canada, a 13% chance of hitting New England, and a 55% chance of never hitting land. One almost certain impact of Katia on the U.S. will be large waves. Long period swells from Katia will begin affecting the Bahamas on Sunday night, then reach the Southeast U.S. by Monday morning. By Tuesday morning, the entire U.S. East Coast will see high surf from Katia, and these waves will increase in size and power as the storm grows closer. Given the slow movement of Katia as it approaches the coast, plus its expected Category 1 to 3 strength as it approaches, the storm will probably cause extensive beach erosion and dangerous rip tides for many days.

94L
A well-organized low pressure system with a surface circulation but limited heavy thunderstorm activity due to high wind shear is 450 miles south of Halifax, Canada. This disturbance, (94L), is headed northeast out to sea, and is being given a 60% chance of developing into a tropical depression by NHC. 94L is under a high 25 - 30 knots of wind shear, but this shear is expected to fall to the moderate range, 10 - 20 knots, by Saturday morning. However, sea surface temperature will fall from 27°C today to 25°C Saturday morning underneath 94L, and the storm will have a very short window of time to get organized enough to get a name. At this point, it's really a subjective judgement call on whether or not 94L is already a tropical storm.


Figure 5. A Portlight volunteer works to clear storm debris from Hurricane Irene in Hollywood, Maryland.

Portlight disaster relief effort in Maryland
Hurricane Irene heavily damaged the town of Hollywood, Maryland, when a tornado cut off electric power, water, and phone service. Portlight and Team Rubicon volunteers arrived before emergency personnel, after following up on a local tip. What they found was an isolated area whose plight was unknown to the larger community. Most residents were trapped at their homes by heavy debris. Portlight and Team Rubicon worked for two days to clear paths to each address, extract vehicles from debris, and cut down trees that constituted safety hazards. Portlight also instructed local residents how to operate and maintain chainsaws and safely clear debris. No other volunteer organizations or emergency personnel arrived at any time, and Portlight succeeded in meeting the specific needs of the underserved, unserved, and forgotten. Visit the Portlight blog to learn more; donations are always welcome.

I'll have a new post each morning over the coming holiday weekend; wunderground meteorologists Angela Fritz, Rob Carver, and Shaun Tanner will be handling the afternoon and evening posts. Have a great holiday weekend, everyone!

Jeff Masters

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Yes, that is why I lurk here a bunch. Good information, even from those who are just funny, or have opinions...

Like "in the cone" the divergence in the models are a little disturbing. I would watch it, but would say the chances of Katia affecting south florida to be less than 5% (and I might be generous there).

Quoting connie1976:


Thank you for the explanation! I usually get really good answers here... I will find out info here and sure enough it's right a lot of the time...but I know to rely on the nhc....but it's always fun to get the opinions of everyone here!
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Quoting LightningCharmer:
Most insurance companies that I've with which I've dealt will not let you bind a policy during a named storm, at least that's for south Florida.


Ditto in South AL.
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Quoting InTheCone:


That's because I installed a 20k watt generator after Wilma, best shield ever!!!

I knew if spent all that $$ a storm would stay away - just look what it did to Irene - LOL!

Just hope it keeps working!


...it always happens that way! lol I was talking to someone the other day who also got a generator hooked up to their house and spent tons of money and haven't had to use it even once....but I'm sure that it's nice to know that you have it! we don't have a generator, so we definately don't want a storm to come our way! lol
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Quoting Skyepony:
Thanks for the excellent blog update.. explaining how rig obs that are 100s of feet in the air aren't surface winds & the effects of Talas on down the road. Tropics is so tied together around the world.


94L may get declared yet..it's finally detached from it's til now trailing low.


Is 94L remnants of Irene?
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The center still appears to be jumping around some...

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Quoting HoustonTxGal:
Well shoot!  I was really hoping we here in TX would get some rain out of 13 but it seems as though we are out of luck...AGAIN!!

NO FAIR!


No kidding. Looks like we may get some outer bands at best but the track is away from Houston. Maybe a bucket brigade from NOLA?
Member Since: August 30, 2008 Posts: 0 Comments: 173
Quoting InTheCone:


That's because I installed a 20k watt generator after Wilma, best shield ever!!!

I knew if spent all that $$ a storm would stay away - just look what it did to Irene - LOL!

Just hope it keeps working!
Want it to rain, wash your car...
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129. jpsb
Quoting lowerbamagirl:


It is very important when it comes to insurance. If we get damage from a TD (unnamed) we pay a $250 deductible. If we get damage from a "named" storm, we pay a $19,000 deductible. Big difference!
Wow, that is a big difference, thanks, so if NHC is slow to upgrade a system they are in effect helping folks save $$$$$. In that case I can understand a reluctance to upgrade if they is a reasonable doubt.
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Quoting connie1976:
divdog, u seem to be a cranky jerk.


Perhaps, keep in mind, I'm more of a rambunctious jerk, there is a difference.
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Quoting jpsb:
Not understanding the seemingly great concern over the official status of some tropical system. Is there a reason, other then ego, that the official status comes to play in? Like insurance monies, or FEMA help? tia.
Most insurance companies that I've with which I've dealt will not let you bind a policy during a named storm, at least that's for south Florida.
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From the MIT site.

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Good thing college football is on tomorrow. Good excuse to stay in and not feel like I should be doing something outside.
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Quoting connie1976:


awww... thank you! I moved to South Florida from Orlando 5 years ago and was told that the hurricanes will get me here.....haven't had one yet!! lol


That's because I installed a 20k watt generator after Wilma, best shield ever!!!

I knew if spent all that $$ a storm would stay away - just look what it did to Irene - LOL!

Just hope it keeps working!
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Quoting Patrap:
Seen a lotta IR images,, but never one with two Lobes like diz un.





Warthog!
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Quoting scott39:
So does that mean it could be farther down in the GOM?


I don't believe so.
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Quoting Bootsie1:
What is the difference between a TD and a TS? I live in south central MS, about an hour NW from Hattiesburg and an hour and a half SE from Jackson, and need to know if I should start getting my hurricane supplies ready?


A tropical depression has winds of less than 39mph. A tropical storm has winds from 39mph to 73mph. It is possible that TD13 could become a hurricane before making landfall. However, because of its slow movement, it is unlikely to be a hurricane in Mississippi if it ever becomes one at all. You should be prepared for extremely heavy rainfall and possibly gusty winds up to 50mph.
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Quoting MississippiWx:


Refresh it. Should say 1500UTC September 2.


I can't :-(

It's cached at the proxy server.

It does this sometimes. It's good to know that I was at least reading the map right. I was just not seeing the right map!
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Quoting firematt255:
Quoting thesituation:
...and giving updates about snooki sightings...
Just awoke from a nap, and we're up to the "S" storm already.

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118. Skyepony (Mod)
Thanks for the excellent blog update.. explaining how rig obs that are 100s of feet in the air aren't surface winds & the effects of Talas on down the road. Tropics is so tied together around the world.


94L may get declared yet..it's finally detached from it's til now trailing low.
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WE NEED RAIN IN TEXAS, PLEASE COME THIS WAY MR. STORM!
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Quoting Goldenblack:
Its okay Connie. It is just that people other than you have been ruining questions such as "is it coming to my area" with their actions during Irene. Some people on here have become a little short about it. It is the effect of what has already been a very tiring hurricane season.



Thank you for the explanation! I usually get really good answers here... I will find out info here and sure enough it's right a lot of the time...but I know to rely on the nhc....but it's always fun to get the opinions of everyone here!
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there probably will be constant recon flights occuring in the near future. at least they don't have very far to fly.
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Quoting GetReal:


Very impressive outflow in all the quads, except for on the west side. And as was just pointed out, it does appear that the COC may now be under the convection (barely).
So does that mean it could be farther down in the GOM?
Member Since: June 13, 2009 Posts: 0 Comments: 6706
Quoting Patrap:



where are the Ark plans ?, you had them last


I think Pat has the ark plans and I'm looking for him.
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ESL by LSU TD-13 Low Cloud Loop

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What is the difference between a TD and a TS? I live in south central MS, about an hour NW from Hattiesburg and an hour and a half SE from Jackson, and need to know if I should start getting my hurricane supplies ready?
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Quoting lowerbamagirl:


Slip and Slide? Who needs one of those, we just use our blue FEMA tarps from storms of yesteryear!
Nice .. at least they will be out of your hair for a while which should help keep your insanity levels down.
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Quoting FSUCOOPman:


Just realized my office must be showing a cached version of the map because the time and date stamp on what I'm seeing says 1, September 2011...or yesterday.


Refresh it. Should say 1500UTC September 2.
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Quoting jpsb:
Not understanding the seemingly great concern over the official status of some tropical system. Is there a reason, other then ego, that the official status comes to play in? Like insurance monies, of FEMA help? tia.


It is very important when it comes to insurance. If we get damage from a TD (unnamed) we pay a $250 deductible. If we get damage from a "named" storm, we pay a $19,000 deductible. Big difference!
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Quoting InTheCone:


He certainly wasn't nice to you, and since no one will respond to your question, I will at least throw in my 2 cents.

Keep and eye on Katia for the next few days just to make sure it does eventually turn.


awww... thank you! I moved to South Florida from Orlando 5 years ago and was told that the hurricanes will get me here.....haven't had one yet!! lol
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Its okay Connie. It is just that people other than you have been ruining questions such as "is it coming to my area" with their actions during Irene. Some people on here have become a little short about it. It is the effect of what has already been a very tiring hurricane season.

Quoting connie1976:
divdog, u seem to be a cranky jerk.
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Very impressive outflow in all the quads, except for on the west side. And as was just pointed out, it does appear that the COC may now be under the convection (barely).
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Quoting MississippiWx:


The dashed lines are directly over the center and show a shear tendency of -5 to -10kts.


Just realized my office must be showing a cached version of the map because the time and date stamp on what I'm seeing says 1, September 2011...or yesterday.
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Quoting connie1976:
divdog, u seem to be a cranky jerk.


He certainly wasn't nice to you, and since no one will respond to your question, I will at least throw in my 2 cents.

Keep and eye on Katia for the next few days just to make sure it does eventually turn.
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2km Storm Relative IR Imagery with BD Enhancement Curve

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Quoting Patrap:
Seen a lotta IR images,, but never one with two Lobes like diz un.



What do you mean?
Member Since: June 13, 2009 Posts: 0 Comments: 6706
Seen a lotta IR images,, but never one with two Lobes like diz un.



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97. jpsb
Not understanding the seemingly great concern over the official status of some tropical system. Is there a reason, other then ego, that the official status comes to play in? Like insurance monies, or FEMA help? tia.
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divdog, u seem to be a cranky jerk.
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Quoting Patrap:
TD-13 has no plans for Travel any time soon,,its on Wu-cation in the Central GOM



Where are they saying the center is exactly?
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Quoting divdog:
Come on ... break out the slip and slide and let the kids have a ball. Gotta be creative


Slip and Slide? Who needs one of those, we just use our blue FEMA tarps from storms of yesteryear!
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I don't care what they say about it going to Louisiana. I live a few miles northwest of Galveston, TX and this morning I was out in my garden and the stinkbugs and ants are finding higher ground. The wind is really picking up.
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TD-13 has no plans for Travel any time soon,,its on Wu-cation in the Central GOM

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Quoting FSUCOOPman:


Doesn't that map show shear increasing over TD13? It says the white lines are increasing and the outline of the white lined area covers where TD13 is located.

sorry, if I'm not reading it right...


The dashed lines are directly over the center and show a shear tendency of -5 to -10kts.
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It looks like the COC on TD 13 is now underneath all that convection, definite sign that shear is lessening.
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Lee, Nobody has a problem with that...right??Lol He is starting to pump his chest and get ready for at least a Cat 1 hurricane. IMmostHO.
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Quoting Patrap:

Ooh! doughnut candy! (chomp!) (lifesaving donut or float or whatever flattens and air escapes thru the holes left by the bite)
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PI Your saying 45% chance for Katia to make land fall between North Carolina and Canada, so does this mean there's a 55% chance she makes land fall between South Carolina and the F state?
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About

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