Irene's rains heaviest on record in Vermont; Tropical Storm Katia forms

By: Dr. Jeff Masters , 3:40 PM GMT on August 30, 2011

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Record flooding continues in the Northeast from Irene's torrential rains. Hardest hit was Vermont, where heavy rains in the weeks prior to Irene's arrival had left soils in the top 20% for moisture, historically. Irene dumped 5 - 8 inches of rain over large sections of Vermont, with a peak of 11.23" at Mendo. The reading from Mendo was the greatest single-day rainfall in Vermont's history, according to wunderground's weather historian Christopher C. Burt, beating the 9.92" that fell at Mt. Mansfield on 9/17/1999 during the passage of Tropical Storm Floyd. The 13.30" that fell on East Durham, NY during Irene was just shy of New York State's all-time 1-day rainfall record: 13.70" at Brewster on 9/16/1999, from Tropical Storm Floyd.


Figure 1. Wunderphotographer 43BJAGER recorded this image of a house in Sharon, Vermont, that started out the week on the other side of this underpass.

According to the final Hurricane Irene summary from the NWS, the storm dropped 20" of rain in two locations, one in North Carolina and one in Virginia. Here are the highest rain amounts from the hurricane for each state:

Virginia Beach, VA: 20.40"
Jacksonville, NC: 20.00"
East Durham, NY: 13.30"
Freehold Twp, NJ: 11.27"
Mendon, VT: 11.23"
Ellendale, DE: 10.43"
New Hartford, CT 10.15"
Baxter St. Park, ME: 9.91"
Savoy, MA: 9.10"
Lafayette, PA: 8.82"
Pinkham North, NH: 7.33"
Warren, RI: 5.37"

Tropical Storm Katia forms
Tropical Storm Katia formed this morning in the far Eastern Atlantic off the coast of Africa. Katia will be in a moist, low wind shear environment with ocean temperature 1 - 2°C above the threshold needed to support a hurricane, and should be able to intensify to major hurricane strength when it passes to the north of the Lesser Antilles Islands 5 - 6 days from now. It is possible that some of the outer spiral bands of the storm might bring heavy rain squalls to the northern Lesser Antilles, but it would be a surprise if the core of the storm passed through the islands. The long term fate of Katia is unknown. Dr. Bob Hart's Historical Tropical Cyclone Probability web page suggests shows that tropical storms in Katia's current position have a 19% chance of hitting North Carolina, a 16% chance of hitting Canada, an 11% chance of hitting Florida, and a 47% chance of never hitting land.


Figure 2. The morning run of the GFS Ensemble prediction. The ensemble prediction was done by taking a lower-resolution version of the GFS model and changing the initial distributions of temperature, pressure, and humidity randomly by a few percent to generate an ensemble of 20 different computer projections of where Katia might go. The operational (highest-resolution) version of the GFS model (white line) is usually more accurate, but the ensemble runs give one an idea of the uncertainty in the forecast.

Katia is the 11th named storm this year, and comes a full twelve days before the half-way point of the Atlantic hurricane season. Climatologically, September 10 marks the half-way point. A typical hurricane season has just 10 - 11 named storms, so we've already had a whole season's worth of storms before reaching the half-way point. At this rate, 2011 will see 25 named storms, making it the 2nd busiest season on record, behind 2005. Katia's formation date of August 30 puts 2011 in 5th place for earliest date of arrival of the season's 11th storm. Only 2005, 1995, 1936, and 1933 had an earlier 11th storm.

Gulf of Mexico development possible late this week
Several of our best computer models for predicting formation of tropical cyclones, the GFS and ECMWF, are predicting that an upper level pressure interacting with a tropical wave now over the the Western Caribbean could combine to spawn a tropical depression in the Gulf of Mexico late this week or early next week. The formation location is likely to be off the coast of Louisiana or Texas, but the track of the system is hard to predict at this point.


Figure 3. Portlight volunteer Thomas Hudson clears a driveway yesterday 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 on Wednesday discussing if the evacuations and media hype surrounding Irene were excessive.

Jeff Masters

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Quoting ncstorm:


NOGAPS..
Link



Thank you! :)
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114. JLPR2
GFS 300hrs(fantasy)
Has a system east of the Lesser Antilles after Katia's exit.

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great update levi. thanks for keeping us informed. two quick questions if I may. First, looking at the upper air pattern in the coming days and Katia's forward speed, do you see the possbility that she misses the trough all together?

Second, remember the upper air pattern you were speaking off a week or so ago (strong high setting up along the eastern seaboard)? Has this changed? Or coming soon? thanks!
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Check it out - 850mb vorticity already on the increase in the NW Caribbean along the wave axis:

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and player number 3 enters the game-300 hours

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Our tropical wave in the NW Caribbean is going to have all of the available energy to itself due to the monsoon trough being pretty far north over central America, meaning that the East Pacific will be giving no competition to the Gulf of Mexico anytime soon. This gives an ideal setup for home-grown tropical mischief that could have days to try to gradually wind up, likely not amounting to anything significant until this weekend.
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Quoting GetReal:



IMO Katia COC is near 11.7N and 33.3W on this loop. So far Katia seems to be favoring the southern outskirts of the cone.


i totally agree , right now katia is moving around 275-280 degrees or just a tad n of due west, jmo though
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Quoting CCravey01:
Sorry, but I am asking for this link one more time...The NOGAPS link...I got it off here yesterday and now I can't get back to it. Pretty, pretty please, will someone post that (or any other link to a model that they really trust) ? I'm at work and don't have access to my stuff at home. Thanks, ya'll!


NOGAPS..
Link
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New official coordinates will be interesting... and how models react with them as well..
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Quoting RitaEvac:
Gonna have to have a large system from the gulf and a front stalled out over TX and have the tropical system stall as well. Giving TX a soaking and nothing but a continuous flow from the tropics pouring into the state.


One could only hope.. but then again I'm not for another Allison. Unfortunately should something develop, it look like more SE Texas and up into LA.
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In relation to Katia I heard someone say that they are anticipating for a cold front that would keep Katia to the west. What would that mean for the GOM?

Also, what are the chances that the GOM storm developing?
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216 Hours


240 Hours
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IMO Katia COC is near 11.7N and 33.4W on this loop. So far Katia seems to be favoring the southern outskirts of the cone.
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186 Hours 12z GFS

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Although I don't hope for a storm here, I hope for some good rain soon. I'm sick of smelling like a barbeque pit thanks to this marsh fire. It's killing my respiratory system too. Whole office here reeks and the smell stays in my hair. Can't get away from it.
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Have to go now. Back later today.
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Sorry, but I am asking for this link one more time...The NOGAPS link...I got it off here yesterday and now I can't get back to it. Pretty, pretty please, will someone post that (or any other link to a model that they really trust) ? I'm at work and don't have access to my stuff at home. Thanks, ya'll!
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On an Al Jazeera English Blog there is an article about Hurricane Irene. It must be explained to their general readership,

"It's worth noting that in the US there's a history of city mayors losing office or popularity because of bad decisions about weather."

When it is put into plain words it does sound rather ridiculous, doesn't it?
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Quoting ncstorm:
GOM storm slowly moves toward Texas..
153 Hours 12Z GFS


Wonder what the record is for the longest-lasting Gulf storm.
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Quoting kshipre1:
wow! thanks for the detailed explanation Kman. the thing is that Henry thinks that no trough will be present... that is the scary part

what are your thoughts?


Too far out in time to draw any conclusions at this time. When Katia nears 60 W we will have a better idea of the trough will be.
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If it does develop it will develop rapidly and likely become a hurricane in the NW gulf...water temps are through the roof, 86-88F!


However, after seeing the upper-level 200 mb from the GFS, it forms from an upper-level low, so upper-level shear could inhibit it. So may not form as fast as it appears...we will see.
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Quoting kmanislander:


Too far out in time to say. A lot depends on multiple factors including whether the current coordinates are correct and the forward speed of Katia, which right now is fairly brisk and a testament to the strength of the steering ridge to its North. Think of it this way. Two cars are on separate roads that lead to a common intersection. Whether they will both arrive there at the same time is a function of may variables.

The models forecast how the variable features evolve over time in the atmosphere. If you change one parameter it affects all the others and that is why the models shift up and down and back and forth so often. In the example of the cars, if one driver makes a last minute decision to stop for 10 minutes to get gas and the other driver does not stop, this could mean that they miss each other entirely at the intersection.

We have to wait for Katia to get closer to 60 W before the forecast track will begin to firm up.
Thanks, Good analogy.
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Quoting ncstorm:
storm in the GOM sits over LA for a long time..
132 Hours 12Z GFS



I do not like this arrangement. Based on what is here, that "Whatever" going ashore on the northern GOM will end up on the east coast in a few days. Meanwhile, Katia will be able to drift north to catch it's tail and follow behind.

I do not like that show, can we schedule something else to play at that time?
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Good morning.

Blog update:

Tropical Tidbit for Tuesday, August 30th, with Video
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177 Hours 12Z GFS
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I am located near 13.1 North 61.1 west on the island of St Vincent 90 miles West of barbados , we had an experience with TOMAS last year ( October 30th) , any chance of this having a significant impact on our weather?
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Quoting scott39:
Thanks for this explanation, How strong do you think the trough will be coming off the E Coast, in relation to breaking down the High in the Atlantic? In reference to Katia and possible developement in the GOM tracks?


Too far out in time to say. A lot depends on multiple factors including whether the current coordinates are correct and the forward speed of Katia, which right now is fairly brisk and a testament to the strength of the steering ridge to its North. Think of it this way. Two cars are on separate roads that lead to a common intersection. Whether they will both arrive there at the same time is a function of may variables.

The models forecast how the variable features evolve over time in the atmosphere. If you change one parameter it affects all the others and that is why the models shift up and down and back and forth so often. In the example of the cars, if one driver makes a last minute decision to stop for 10 minutes to get gas and the other driver does not stop, this could mean that they miss each other entirely at the intersection.

We have to wait for Katia to get closer to 60 W before the forecast track will begin to firm up.
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165 Hours 12Z GFS

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wow! thanks for the detailed explanation Kman. the thing is that Henry thinks that no trough will be present... that is the scary part

what are your thoughts?
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GOM storm slowly moves toward Texas..
153 Hours 12Z GFS
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Quoting TexasHurricane:
It seems they they are still hinting at something in the western GOM coming up but I will still believe it when I see it.

We need it to come into TX and go through TX. Not edge up to us ,hang at the coast and go north to LA.

Not trying to take away from LA if they need the rain to, just saying in order for most of TX to benefit that is what it needs to do.

sigh...


We just to wait and see what happens! I agree that we need it to take a hit right into central TX coast and just slowly move northward, but since the storm is not even an "invest" yet we have no idea what will happen.
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81. Oxon
Quoting Dakster:
Actually, if you are in the NE you should be happy the LONG, LONG range models predict a hit. They are very rarely correct that far out. Look at Irene...

Irene was going to be a Gulf Storm this far out. As usual, we need to just sit back and watch and anything can happen.


While I would be delighted to think anything showing Katia making landfall on the East Coast (whether in the US or Canada) was inaccurate, the analogy to Irene doesn't work. GFS early on showed Irene coming up the coast (I remember, because I discussed it with people I know in the NY area) -- then shifted it to the Gulf and then came back to the coast.
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Quoting Seastep:
29. Speeky

Way too early to tell. As of now, everything suggests Bermuda would be the only worry.

As is always said (same as "too early"), things can and do change.

I agree 100%
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Quoting angiest:


That would be a leftmost outlier...


Agreed.
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144 hours..its stalling both systems

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Quoting kmanislander:


The two oceans are interconnected at the atmospheric level.



Yes, I agree, well explained
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Quoting goldenpixie1:


Thanks Dak. Was just wondering odds-wise if it was more or less accurate.


YW. I hope that his odds play out and that Katia misses land... Only time will tell!

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Quoting ncstorm:
114 Hours 12Z GFS


The 12Z run was initialised using coordinates that may now have been too far North. Because Katia is sheared it is difficult to tell where the center is based upon satellite imagery but from what I can see of the cloud movements 12.3 seems to be at least half a degree too far N IMO. I looked at the ADT center fix position and it shows it in the area of convection located at the far NE of the circulation but I am not convinced of that.
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storm in the GOM sits over LA for a long time..
132 Hours 12Z GFS

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Quoting Dakster:


Looks like a 1% chance of hitting Texas....

Thanks for bringing that map in!


That would be a leftmost outlier...
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Quoting Dakster:


Funny thing about statistics.... If you say something has a 1% chance of doing something and it does it - you are still technically "correct".

The higher odds are that this will go out to sea and not affect land - however, there are still chances that it could affect anywhere from Florida to Maine... And he wouldn't be "wrong". Now if it goes into Texas -- his odds didn't address that possibility so I can only "assume" (and we know what happens when we do that) that this scenario has never happened.


Thanks Dak. Was just wondering odds-wise if it was more or less accurate.
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How for sure are you guys that this storm will go out to sea? What would prevent it from going out to sea?
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Quoting ncstorm:
114 Hours 12Z GFS
That looks like more rain for La. Miss. and Al. than Texas.
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Quoting P451:
In case they were missed: Both were 6z's.


GFS Runs:







ECMWF Runs:





What's the link to the website for these model runs? I would really like to use it in the future
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Kman, thank you for taking the time to explain that.
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Quoting angiest:


FWIW, 1900 or 1915 started out there:



Looks like a 1% chance of hitting Texas....

Thanks for bringing that map in!
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Check out the Tropical Storm Katia FanPage on Facebook
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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