Irene slightly weaker, but still very dangerous

By: Dr. Jeff Masters , 8:59 PM GMT on August 25, 2011

An Air Force Reserve hurricane hunter aircraft investigating Irene has found a slightly weaker storm. As of 4pm EDT, the strongest surface winds seen by the aircraft with their SFMR instrument were 91 mph in the storm's northeast eyewall. Highest winds measured at their flight level of 10,000 feet were 114 mph. Assuming the aircraft missed sampling the strongest winds of the hurricane, it's a good guess that Irene has fallen to Category 2 strength with 100 - 105 mph winds, even though the official advisory is higher. The aircraft noted that the eyewall was missing a large chunk on it southwest side, but the central pressure was about the same as early this morning, 950 mb. Satellite imagery from late this morning and early this afternoon showed a distinctly lopsided appearance to Irene's cloud pattern, with not much heavy thunderstorm activity on the southwest side. This was due to moderate wind shear of 10 - 20 knots due to upper-level winds out of the southwest. This shear was able to disrupt Irene's circulation while it was attempting to complete an eyewall replacement cycle, resulting in dry air getting wrapped into the core, which can be seen as a streak of darker clouds in this morning's MODIS satellite image (Figure 1.) satellite loops show that Irene is beginning to recover from this adversity, with a respectable amount of heavy thunderstorms beginning to wrap around to the southwest side from the north. An upper-level wind analysis from the University of Wisconsin CIMSS site shows that Irene's upper-level outflow is much more restricted than was the case 24 hours ago. An upper-level outflow channel that was open to the south is gone, and has been replaced by shearing winds from the west and southwest that are ripping into the hurricane. I think it is 30% likely that Irene will have trouble recovering from this setback, and will not reach the peak intensity of 120 mph winds it had earlier. However, it is more likely that the hurricane will be able to re-establish its upper-level outflow and overcome the shear, based on the latest satellite loops, plus forecasts from the various hurricane models such as the GFDL, HWRF, and ECMWF, which all show Irene at Category 3 strength as it approaches North Carolina on Saturday afternoon.


Figure 1. MODIS satellite image of Hurricane Irene taken at 11:50 am EDT Thursday August 25, when Irene was a Category 3 hurricane with 115 mph winds. The eye of the storm was just off the coast of Abaco Island in the Bahamas. Note the rather squashed appearance of the hurricane, with less heavy thunderstorms on its southwest side. Upper level winds of 10 - 20 knots out of the southwest were eating away at the clouds on this side, and you can see that this shear helped drive some dry air into the hurricane, which can be seen as a darker strip of cloud spiraling into the center from the south, around the east side, then into the center along the northwest side of the storm. Image credit: a href=http://rapidfire.sci.gsfc.nasa.gov/gallery/ NASA.

Irene likely to bring destructive fresh water flooding
In this morning's post, I highlighted the threat from storm surge flooding, but flash flooding and river flooding from Irene's torrential rains are also a huge threat. The hurricane is expected to bring rains in excess of 12" to 100-mile swath from Eastern North Carolina northwards along the coast, through New York City. The danger of fresh water flooding is greatest in northern New Jersey, Southeast Pennsylvania, and Southeast New York, where the soils are saturated from heavy August rains that were among the heaviest on record. At Philadelphia, rainfall so far this August has been 13 inches, not far from the record for rainiest month of all-time, the 15.82" that fell in August 1867. This record will almost certainly be broken when Irene's rains arrive. In general, the heaviest rains will fall along the west side of the hurricane's track, and the greatest wind damage will occur on the east side. Right now, it does not appear that tornadoes will be a major concern, but there will probably be a few weak tornadoes. Hurricane Bob of 1991, the last hurricane to affect New England, spawned six tornadoes, most of them weak F-0 and F-1 twisters.


Figure 2. Predicted rainfall for the 5-day period ending at 8 am EDT Tuesday August 30, as issued by NOAA/HPC.

Latest forecast for Irene
The latest set of model runs don't show any major changes to Irene's track or intensity. Irene will bring damaging winds, torrential rains, and an extremely dangerous storm surge to the coast, affecting a huge area of the mid-Atlantic and New England. Take this storm seriously! Expect widespread disruptions to electric power, transportation, and water systems. Be prepared for many days without power, as utility crews will be overwhelmed with the damage. Irene is capable of inundating portions of the coast under 10 - 15 feet of water, to the highest storm surge depths ever recorded. I strongly recommend that all residents of the mid-Atlantic and New England coast familiarize themselves with their storm surge risk. The best source of that information is the National Hurricane Center's Interactive Storm Surge Risk Map, which allows one to pick a particular Category hurricane and zoom in to see the height above ground level a worst-case storm surge may go. If you prefer static images, use wunderground's Storm Surge Inundation Maps. If these tools indicate you may be at risk, consult your local or state emergency management office to determine if you are in a hurricane evacuation zone. Mass evacuations of low-lying areas along the entire coast of New Jersey, Delaware, Maryland, and Virginia are at least 50% likely to be ordered by Saturday. The threat to the coasts of New York, Connecticut, Rhode Island, Massachusetts, New Hampshire, and Maine is less certain, but evacuations may be ordered in those states, as well. Irene is a very dangerous storm for an area that has no experience with hurricanes, and I strongly urge you to evacuate from the coast if an evacuation is ordered by local officials. My area of greatest concern is the coast from Ocean City, Maryland, to Atlantic City, New Jersey. It is possible that this stretch of coast will receive a direct hit from a slow-moving Category 2 hurricane hitting during the highest tide of the month, bringing a 10 - 15 foot storm surge.

Links
For those of you wanting to know your odds of receiving hurricane force or tropical storm force winds, I recommend the NHC wind probability product.

Wunderground has detailed storm surge maps for the U.S. coast.

The National Hurricane Center's Interactive Storm Surge RIsk Map, which allows one to pick a particular Category hurricane and zoom in, is a good source of storm surge risk information.

Wunderblogger Mike Theiss is in Nassau, documenting the storm's impact on the Bahamas.

Jeff Masters

Irene Rainband from downtown Ft. Lauderdale (pho)
8/25/11 0910 local time.
Irene Rainband from downtown Ft. Lauderdale
HurricaneIreneIsOutThere! (trigirl)
Early at the beach to snap the waves from Hurricane Irene east of our coast, the wind was unreal with thunderclouds rolling in with lots of rain for the day.
HurricaneIreneIsOutThere!

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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Quoting Seawall:


LOL, I'm a woman, I guess you can ask me about my unit... too funny.


I'm married so i will have to pass.
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Quoting Seawall:


I've not fried mine with a generator, with a surge protector in between, but I've heard recommendations not to do so... so do at your own risk... :)


Surge protector definitely wouldn't do it ... you would need a good battery UPS with power conditioning ... if that would work :) ... I guess the question is really can you run a good UPS off a generator?
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looking at all these track models the nhc forecast and the others just to the east seem to be the worst case scenario,clipping NC and then over water all the way to NYC or just east of there, it doesnt appear it will go any further west,so it eases a bit the damage for the I-95 corridor dc,philly,but NYC and east..........OUCH!
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Quoting bwat:
Really dude? I'll take time zones for $1,000 Alex.


I'll take Sarcasm for 2,000
Member Since: December 31, 1969 Posts: Comments:
ACE is the wind speed in knots, squared, then divided by 10,000. For a storm, you sum it for each advisory.

35 kts = .1225
40 kts = .16
45 kts = .2025
50 kts = .25
55 kts = .3025
60 kts = .36
65 kts = .4225
70 kts = .49
75 kts = .5625
80 kts = .64
85 kts = .7225
90 kts = .81
95 kts = .9025
100 kts = 1
105 kts = 1.1025
110 kts = 1.21
115 kts = 1.3225
120 kts = 1.44
125 kts = 1.5625
130 kts = 1.69
135 kts = 1.8225
140 kts = 1.96
145 kts = 2.1025
150 kts = 2.25
155 kts = 2.4025
160 kts = 2.56
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2286. Seawall
Quoting WatchingThisOne:


Can you run a computer off a generator if you have a good UPS unit between them?


I've not fried mine with a generator, with a surge protector in between, but I've heard recommendations not to do so... so do at your own risk... :)
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Just as a frame of reference, 943 mbar is about the same as being 2200 feet above mean sea level. That's kinda interesting if you think about it that way.
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2284. bwat
Quoting PrivateIdaho:


The hours are longer in Alaska?....who knew?
Really dude? I'll take time zones for $1,000 Alex.
Member Since: December 31, 1969 Posts: Comments:
TS force winds out to 290. Well if TS winds extend that far on BOTH side (Unlikely I guess) but that would make the storm almost 600 miles wide. That is Astonishing!
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2282. Seawall
Quoting PrivateIdaho:


don't ask a man about his unit in here

Re ported.


LOL, I'm a woman, I guess you can ask me about my unit... too funny.
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Quoting Seawall:


Mine is a 5500, a small one, but it will work if you rotate the appliances out. I think the starting power is 7500 on it, but it is 5500 watts to maintain the power. You don't have to have the refrig plugged in all the time, if it's efficient, you can choose to unplug it. Not recommending this during normal operation, but in an emergency, you can sure save a lot of things and be a tad more confortable. Just a tad, it's not a luxury. I was able to plug in the washing machine during Rita.. it helped.
thank you
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Quoting Seawall:


Mine is a 5500, a small one, but it will work if you rotate the appliances out. I think the starting power is 7500 on it, but it is 5500 watts to maintain the power. You don't have to have the refrig plugged in all the time, if it's efficient, you can choose to unplug it. Not recommending this during normal operation, but in an emergency, you can sure save a lot of things and be a tad more confortable. Just a tad, it's not a luxury. I was able to plug in the washing machine during Rita.. it helped.


Can you run a computer off a generator if you have a good UPS unit between them?
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Pretty substantial difference between the western and eastern sides of Irene.
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2278. NJ2S
Quoting mojofearless:

I had some really good times in Weehawken. My thoughts will be with you guys in Jersey. Really concerned about Asbury Park - I just discovered how shab-u-lous it is about a month ago, and fell head over heels for the architecture of the Paramount and Convention Hall, and the people too of course.
Good luck and wishing you the best from NOLA


thanks! we def need it....if she nudges east thats better for us worse for long island and new enegland
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Quoting Ryuujin:
He lives in 'laska. That's plenty of sleep.


The hours are longer in Alaska?....who knew?
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2276. Seawall
Quoting HurricaneHunterJoe:
what size unit are you talking?


Mine is a 5500, a small one, but it will work if you rotate the appliances out. I think the starting power is 7500 on it, but it is 5500 watts to maintain the power. You don't have to have the refrig plugged in all the time, if it's efficient, you can choose to unplug it. Not recommending this during normal operation, but in an emergency, you can sure save a lot of things and be a tad more confortable. Just a tad, it's not a luxury. I was able to plug in the washing machine during Rita.. it helped.
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2275. nigel20
Quoting trHUrrIXC5MMX:


you can calculate ACE by yourself using a table...

35 kt = 0.1225
40 kt = 0.16
45kt = 0.2025
50 kt = 0.25
55 kt = 0.36

65 kt = 0.7225
100 kt = 1.00

and so on...

Thanks, very useful info.
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Oh good, the models are still consistently saying Boston's not going to have fun. I'm half-tempted to leave tomorrow night.
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Night Miami, night Levi thanks for your always valued input :)
Member Since: December 31, 1969 Posts: Comments:
Quoting victoriahurricane:


The TCHP (Tropical Cyclone Heat Potential) supports a storm that has 140 to 160 kt winds, essentially it can support a Cat 5.


oh got yah! oh by the way no change in the 2 am adv.
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My other prediction is that if Irene goes anywhere close to Jacksonville NC the Marines will kick her @ss.
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2270. Ryuujin
Quoting PrivateIdaho:


Enjoy your less than 4 hours of sleep....(yikes!!)
He lives in 'laska. That's plenty of sleep.
Member Since: December 31, 1969 Posts: Comments:
...IRENE MOVING NORTHWARD AWAY FROM THE BAHAMAS TOWARDS THE NORTH CAROLINA COAST...

2:00 AM EDT Fri Aug 26
Location: 28.7°N 77.3°W
Max sustained: 115 mph
Moving: N at 14 mph
Min pressure: 942 mb
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2268. Ryuujin
All the eastcasters. It was less than 30 NM off the forecast point. This does not mean a sudden huge leap to the Right on the models. I want this thing to go out to sea harmlessly as much as the next guy, but sticking your head in the ground like an Ostrich and going "lalalalalalalala" and pretending that a bit of a E wobble is going to make that much of a difference is just.. mind numbingly ignorant.
Member Since: December 31, 1969 Posts: Comments:
Quoting nigel20:
Current Accumulated Cyclone Energy (ACE) 27.3
Irene's ACE 14.1
via wiki


I would think that ACE is not the best measure here, as it is based on maximum sustained wind speed. It would be artificially low in a storm like this where a lot of the energy is going to be in the surge and waves as opposed to the wind.

IKE is a different matter. That's what we should be looking at.

Or am I wrong?
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Quoting MiamiHurricanes09:
Why thank you sir, lol.

I'm out for the night, gotta wake up early like usual. Good night everyone.


JFV has been among us all along =O j/k couldn't resist.
Member Since: December 31, 1969 Posts: Comments:
942 MB and still at 115 MPH

I dont remember any storm with a pressure that low that kept getting lower and didn't upgrade it's wind field.
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2264. nigel20
IRENE IS A LARGE TROPICAL CYCLONE. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 80 MILES...130 KM...FROM THE CENTER...AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 290 MILES...465 KM. NOAA
BUOY 41010 LOCATED ABOUT 140 MILES...220 KM EAST OF CAPE CANAVERAL
FLORIDA RECENTLY REPORTED A SUSTAINED WIND OF 51 MPH...83 KM/H...
AND A WIND GUST OF 67 MPH...108 KM/H.
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Quoting nigel20:
Current Accumulated Cyclone Energy (ACE) 27.3
Irene's ACE 14.1
via wiki


you can calculate ACE by yourself using a table...

35 kt = 0.1225
40 kt = 0.16
45kt = 0.2025
50 kt = 0.25
55 kt = 0.36

65 kt = 0.7225
100 kt = 1.00

and so on...
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Quoting Levi32:
I don't think I'll stay up for the 0z Euro tonight. Gotta get up at 3:30am tomorrow. Goodnight all.


Enjoy your less than 4 hours of sleep....(yikes!!)
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Quoting trHUrrIXC5MMX:


what?


The TCHP (Tropical Cyclone Heat Potential) supports a storm that has 140 to 160 kt winds, essentially it can support a Cat 5.
Member Since: December 31, 1969 Posts: Comments:
Quoting MiamiHurricanes09:
Why thank you sir, lol.

I'm out for the night, gotta wake up early like usual. Good night everyone.


Night MH09!
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Quoting Levi32:
I don't think I'll stay up for the 0z Euro tonight. Gotta get up at 3:30am tomorrow. Goodnight all.


Have an excellent evening!
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Quoting Levi32:
I don't think I'll stay up for the 0z Euro tonight. Gotta get up at 3:30am tomorrow. Goodnight all.


Night Levi catch some good rest!
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Quoting trHUrrIXC5MMX:


what?


Sorry...

sst's = Sea Surface Temperatures

Wisc.edu has a chart that ranks the max potential a storm could get up to in wind knots based on the temperature of the sea that the center of the storm passes over. So, if its really really hot water, the storm could get as high as 160 kts. If its just hot/warm, maybe 140 knots max. Etc.. The hotter the water, the more potential energy exists and the stronger the storm COULD become. Now, other factors play into the equation (shear, eyewall replacement, etc.) But, the potential is there due to the heat content of the ocean.

Get it?
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Track will likely need to be shifted slightly eastward at 5:00am:

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Quoting NJ2S:
Im a long time lurker(for about 5 years) once in a while i comment....i will say I have always been fascinated by the power and some would say beauty of mother nature....i have followed hurricanes closely since i was a kid with Gloria being my first experience....I was always curious(sympathetic) about how it felt and what it took to come to the realization that a monster storm was headed your way endangering yourself loved ones and property...I always assumed that living here in NJ i was at a low risk for such event...this situation is becoming so serious and scary....my heart goes out to everyone who has ever had to face a hurricane(esp the gulf)....not knowing what monday will look like is a scary and uncomfortable feeling....i hope things turn out for the best yet i hope my fellow east coasters are prepared for the worst...

JR in Weehawken, NJ

I had some really good times in Weehawken. My thoughts will be with you guys in Jersey. Really concerned about Asbury Park - I just discovered how shab-u-lous it is about a month ago, and fell head over heels for the architecture of the Paramount and Convention Hall, and the people too of course.
Good luck and wishing you the best from NOLA
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Quoting PrivateIdaho:


Hey I predicted that it would move due West through the Bahamas for days.
LOL
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Quoting Johnhopefan:


I'm willing to bet the '38 Hurricane, which had cat 4 pressure and a cat 3 surge, probably would have only been rated a cat 2 by today's standards if the technology had been available back then to monitor it. That is why I am so worried about Irene, could have cat 4 pressure and a cat 3 surge with a cat 1 or 2 rating so people don't evacuate, and then you have another '38.


Exactly, the whole system needs to be redone or changed.
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2252. Levi32
I don't think I'll stay up for the 0z Euro tonight. Gotta get up at 3:30am tomorrow. Goodnight all.
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Go east, young Irene.
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Quoting HurricaneHunterJoe:
what size unit are you talking?


don't ask a man about his unit in here

Re ported.
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Quoting victoriahurricane:
Have the 0z model runs started/finished yet? Haven't seen any models posted in a long time.
Quoting drg0dOwnCountry:
Could someone post the latest model runs?


Link



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Quoting PrivateIdaho:


Such a polite young man!...Well done!
Why thank you sir, lol.

I'm out for the night, gotta wake up early like usual. Good night everyone.
Member Since: December 31, 1969 Posts: Comments:
Quoting Seawall:
A few new tips.... for those staying....

Have your generator staged before it hits. You will most likely know when you will lose power, or electricity as they call it. Have your extension cords run, with a strong pig tail coming right out of the generator. Don't wire the generator up to your house hold breaker box unless you know what you are doing.. it's lethal to the power workers trying to restore your power, or electricity, later.
Have your generator full, and have at least two five gallon gas cans full close, but not adjacent to it. You don't want to have to search for them later, or if the ground is wet, you don't want to walk on it, dragging those heavy cans. Have the duct tape ready to tape down your cords, unless you have carpet...
Run a big extension cord down the main of your house, then put a six way outlet on it; then run another cord down that outlet. Run another large cord to your frig, then another smaller one to the tv, fan, etc. On the other cord, run a small AC unit in the bedroom. Just use common sense, you can also use the cord for the frig for making coffee, and a microwave, but not the same time. It's not easy, but it is doable. Good luck to all on the East Coast. Also, it is NOT recommended to run a computer off of a generator; power surges might fry it. I've done it with luck, but not sure I would try it again.
what size unit are you talking?
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2246. nigel20
Current Accumulated Cyclone Energy (ACE) 27.3
Irene's ACE 14.1
via wiki
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My last post was projected wave heights. I don't know why the legend did not show.
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Quoting dracko19:
FYI: SST's are at 140kts to 160kts max potential in Irene's path until she gets beyond NC. Plenty of fuel for that fire.



what?
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FYI: SST's are at 140kts to 160kts max potential in Irene's path until she gets beyond NC. Plenty of fuel for that fire.

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Quoting victoriahurricane:


I've been thinking about this for a long time and I agree. Most people now only pay attention to the category of the storm and thus you go up to anyone on whether they'll evacuate and they say Cat 3 or higher. One of the costliest storms to ever hit the U.S. wasn't even a hurricane. They don't take into consideration the size, rainfall or surge of the storm, which IMO are more important then wind speed. The whole scale desperately needs a revamping, otherwise complacency among the population will continue to grow.


I'm willing to bet the '38 Hurricane, which had cat 4 pressure and a cat 3 surge, probably would have only been rated a cat 2 by today's standards if the technology had been available back then to monitor it. That is why I am so worried about Irene, could have cat 4 pressure and a cat 3 surge with a cat 1 or 2 rating so people don't evacuate, and then you have another '38.
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2241. bwat
Went to sleep at 9:30pm with nnw movement. Woke up, decided to look at the situation before going back to sleep to find Irene moved slightly east of the forecast track. Now I can't go back to sleep. Does anyone think this slight eastward movement will keep irene from comming as far inland in NC? Current track brings the eye of her right over me in NE NC. Maybe I need to just go back to sleep, made her go eastward slightly last time. Lol.
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather

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