Is U.S. climate getting more extreme?

By: Dr. Jeff Masters , 1:54 PM GMT on March 13, 2009

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Is the climate in the U.S. getting more extreme? The answer to this question depends upon how one defines "extreme". For example, the number of extreme tornadoes (violent EF-4 and EF-5 twisters) has not increased in recent years. We lack the data to judge whether there has been an increase in severe thunderstorms and hail. There has been a marked increase in Atlantic hurricane activity since 1995 (though the possible contribution of human-caused global warming to this increase is not something hurricane scientists agree upon). Since it is difficult to quantify how severe storms like tornadoes and hurricanes are changing, a better measure of how climate extremes are changing is to look at temperature and precipitation, which are well-measured. NOAA's National Climatic Data Center (NCDC) has developed a Climate Extremes Index to attempt to quantify whether or not the U.S. climate is getting more extreme. The Climate Extremes Index (CEI) is based upon three parameters:

1) Monthly maximum and minimum temperature
2) Daily precipitation
3) Monthly Palmer Drought Severity Index (PDSI)

The temperature data is taken from 1100 stations in the U.S. Historical Climatology Network (USHCN), a network of stations that have a long period of record, with little missing data. The temperature data is corrected for the Urban Heat Island effect, as well as for station and instrument changes. The precipitation data is taken from 1300 National Weather Service Cooperative stations. The Climate Extremes Index defines "much above normal" as the highest 10% of data, "much below normal" as the lowest 10%, and is the average of these five quantities:

1) The sum of (a) percentage of the United States with maximum temperatures much below normal and (b) percentage of the United States with maximum temperatures much above normal.

2) The sum of (a) percentage of the United States with minimum temperatures much below normal and (b) percentage of the United States with minimum temperatures much above normal.

3) The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.

4) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.

5) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.


Figure 1. The Annual Climate Extremes Index (CEI), updated through 2008, shows that U.S. climate has been getting more extreme since the early 1970s. Image credit: National Climatic Data Center. On average since 1910, 20% of the U.S. has seen extreme conditions in a given year (thick black line).

As summarized by Gleason et al. (2008), the National Climatic Data Center concludes that based on the Climate Extremes Index, the percentage of the U.S. seeing extreme temperatures and precipitation generally increased since the early 1970s. These increases were most pronounced in the summer. No trend in extremes were noted for winter. The annual CEI index plot averaged for all five temperature and precipitation indices (Figure 1) showed that five of the fifteen most extreme years on record occurred since 1997. Shorter-lived periods with high CEI values occurred in the 1930s and 1950s, in association with widespread extreme drought and above-average temperatures. The most extreme year in U.S. history was 1998, with 1934 a close second. The year 1998 was the hottest year in U.S. history, with a record 78% of the U.S. experiencing minimum temperatures much above normal. That year also had a record 23% of the U.S. with much greater than normal precipitation from extreme 1-day precipitation events. The 1934 extreme in CEI was due in large part because of the most widespread drought of the century--a full 52% of the U.S. was affected by severe or extreme drought conditions. That year also saw a record 64% of the U.S. with much above normal maximum temperatures.

The impact of maximum and minimum temperatures on the Climate Extreme Index
It is very interesting to look at the five separate indices that go into the Climate Extremes Index. Today I'll look at temperature, and next week, I'll focus on drought and precipitation. The portion of the U.S. experiencing month-long maximum temperatures either much above normal or much below normal has been about 10% over the past century (black lines in Figure 2). However, over the past decade, about 20-25% of the U.S. has been experiencing monthly maximum temperatures much above normal, and the portion of the U.S. experiencing much colder than normal high temperatures has been near zero. Minimum temperatures show a similar behavior, but have increased more than the maximums (Figure 3). Over the past decade, minimum temperatures much above normal have affected 25-35% of the U.S. This means that the daily range of temperature (difference between minimum and maximum) has decreased over the past decade, which is what global warming says should be happening if greenhouse gases are primarily to blame for the rise in temperatures.

While there have been a few years (1921, 1934) when the portion of the U.S. experiencing much above normal maximum temperatures was greater than anything observed in the past decade, the sustained lack of maximum temperatures much below normal over the past decade is unique. The behavior of minimum temperatures over the past decade is clearly unprecedented--both in the lack of minimum temperatures much below normal, and in the abnormal portion of the U.S. with much above normal minimum temperatures. Remember that these data ARE corrected for the Urban Heat Island effect, so we cannot blame increased urbanization on the increase in temperatures. Recall that the all-time record maximum and minimum temperature data, which I presented in a post in February, are not corrected for the Urban Heat Island Effect, but look very similar to the CEI maximum and minimum temperature trends presented here.

A lot of people have told me that they believe we are experiencing more wild swings of temperature from hot to cold from day to day in recent years, but the CEI data does not answer this question. To my knowledge, a study of this kind has not been done.


Figure 2. The Annual Climate Extremes Index (CEI) for maximum temperature, updated through 2008, shows that 20-25% of U.S. has had maximum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.


Figure 3. The Annual Climate Extremes Index (CEI) for minimum temperature, updated through 2008, shows that 25-35% of U.S. has had minimum temperatures much above normal over the past decade. Image credit: National Climatic Data Center.

References
Gleason, K.L., J.H. Lawrimore, D.H. Levinson, T.R. Karl, and D.J. Karoly, 2008: "A Revised U.S. Climate Extremes Index", J. Climate, 21, 2124-2137.

Annual WeatherDance contest ready for registration!
Armchair forecasters, now's your chance to shine! WeatherDance, based on teams in the men's and women's NCAA basketball tournaments, allows players to predict which team's city will be hotter or colder on game day in each round of the Big Dance. Beginning today, players can make their forecasts at the Weather Dance Web site at: www.weatherdance.org. The site will be updated with cities promptly after NCAA seeding announcements. First round Weather Dance selections must be entered by 11:59 p.m. EDT Wednesday, March 18.

"Officially, Weather Dance began as a class project to get students involved in weather forecasting, but we kept it around because it got popular. People think they can do better forecasting than the meteorologists. Well, here's their shot!" said Perry Samson, WeatherDance creator, co-founder of the The Weather Underground, Inc., and Professor in the Department of Atmospheric, Oceanic and Space Sciences at the University of Michigan.

This is the fifth year for the game. Last year more than 2,000 people played. Most play merely for the thrill, but many K-12 science teachers involve their classes as part of meteorology units. The winning teacher will receive an expense-paid trip to join the Texas Tech/University of Michigan Storm Chasing team this spring for a day of tornado chasing in Tornado Alley. Other winners will receive a Weather Underground umbrella, "Extreme Weather" mugs, or a copy of the book "Extreme Weather," by Christopher C. Burt.

I'll talk about drought and precipitation trends in my next post, Monday or Tuesday.

Jeff Masters

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The Teams are picked and the Tourney is set.....join the Charity Event for the first annual Portlight Charity March Maddness drive! Details are on my Web site if anyone would like to Play for a small Donation and alot of smack talk....LOL

http://tampaspinsweather.webs.com/index.htm

If anyone has any questions email!

Thanks for the Support as someone will be in need this Summer. You can bet on it!

Tim
Member Since: September 2, 2007 Posts: 179 Comments: 20448
What a sight! Amazing and Beautiful! Godspeed to the 13-day mission.
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Quoting zoomiami:
This is the first time in years that I've been able to see the shuttle from here in Miami - it lit up the sky going up - wish I had been able to take a pic.


Ya here in port st lucie it was a great site but i couldnt find my camera lol
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This is the first time in years that I've been able to see the shuttle from here in Miami - it lit up the sky going up - wish I had been able to take a pic.
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Spectacular!!
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I just watched it from my house. amazing
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All systems go for the 125th shuttle flight. About 5 minutes away.
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Hi Baha - finally on at the same time. How are you?
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Quoting RMM34667:
Skies are so clear we should get an awsome view here in the Tampa Bay area too. Just wish is was taking off about a half hour later. When the fire lights up the dark sky the sight give chills..

Watching the count down clock!!
Reminds me of some Ray Bradbury stuff.
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Skies are so clear we should get an awsome view here in the Tampa Bay area too. Just wish is was taking off about a half hour later. When the fire lights up the dark sky the sight give chills..

Watching the count down clock!!
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Lift off at 7:43 EST. Gonna be cool to be able to see it down here in West Palm.
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Quoting Patrap:
The Spice's must FLow..LOL

The Lake Huron Cyclone 96'


An intense cutoff low developed over the Great Lakes during the period 11-15 September 1996. As the low deepened, height falls in the lower troposphere exceeded those at upper levels, the cold core low evolved into a warm core system, and vertical wind (speed and directional) shear decreased dramatically.



Darn it, Patrap... you just had to show me that there are hurricanes on the Great Lakes... here I was thinking MI was pretty safe from those.

Anyone remember me? (Who is not on Rob's blog)
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259. Orcasystems
Stay safe - will be watching your critter/weather cam!
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WIND WARNING: Greater Victoria - Issued at 1:56 PM PDT SUNDAY 15 MARCH 2009

WIND BECOMING SOUTHWEST 60 TO 80 KM/H EARLY THIS EVENING. THIS IS A WARNING THAT POTENTIALLY DAMAGING WINDS ARE EXPECTED OR OCCURRING IN THESE REGIONS. MONITOR WEATHER CONDITIONS..LISTEN FOR UPDATED STATEMENTS.
AN INTENSE LOW PRESSURE SYSTEM WILL TRACK EASTWARD ACROSS VANCOUVER ISLAND EARLY THIS EVENING. IN THE WAKE OF THE LOW STRONG WINDS SOUTHWEST 60 TO 80 KM/H WILL DEVELOP OVER THE ABOVE MENTIONED REGIONS OF THE INNER SOUTH COAST AND PORTIONS OF VANCOUVER ISLAND. WINDS ARE EXPECTED TO EASE OVERNIGHT AS THE LOW PRESSURE SYSTEM TRACKS FURTHER INLAND.
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Shuttle crew is inside the space shuttle!
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ANALYSIS: Possible Rainfall Next Week for South Florida?
Photobucket

Based upon all the computer models, the frontal boundary currently lingering over the SE US will get some push towards the south and move into Southern Florida. Once the front arrives, it will stall out over the area. At ths time, the atmosphere here in South Florida is increasingly becoming more moist and slightly more unstable and will continue to do so as the front comes into the area later Tuesday into Wednesday. By the time the front arrives, there should be a moist and unstable enough atmosphere to sustain showers and even some isolated thunderstorms. If this front does indeed stall, it would serve as a lifting mechanism for the development of showers and storms. But, as always, we will have to wait and see how this entire situation evolves over time and through further model runs.
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only problem being so dry most of what ever falls will run off with ground being compacted so hard unless a 3 or 4 day event with light steady rains occur it may not make much of a difference
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Quoting KEEPEROFTHEGATE:
the only problem cchs is models are meant to be taken as guidance only and do not depict final outcome we know something is possible exactly what remains to be seen hopefully ya get the water most of ya need it anyway


Hence why I made the point in saying "Just hoping this does come true."
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Quoting cchsweatherman:
See that many people have become concerned about the drought situation in Florida, especially Southern Florida. Well, the 12Z GFS paints a nice picture for Southern Florida showing decent rainfall this coming week. Just hoping this does come true since we need the relief.


Figure 1 12Z GFS Forecast Rainfall Next Five Days (Source: Raleigh Weather)

EDIT: Just checked all the other models and it seems they're all in agreement that all South Florida will receive some needed rainfall come Wednesday through Saturday.
the only problem cchs is models are meant to be taken as guidance only and do not depict final outcome we know something is possible exactly what remains to be seen hopefully ya get the water most of ya need it anyway
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Quoting hahaguy:
cchs but the thing is will the front dry up or not by the time that it gets to all of us in south florida.


Based upon all the computer models, the frontal boundary currently lingering over the SE US will get some push towards the south and move into Southern Florida. Once the front arrives, it will stall out over the area. At ths time, the atmosphere here in South Florida is increasingly becoming more moist and slightly more unstable and will continue to do so as the front comes into the area later Tuesday into Wednesday. By the time the front arrives, there should be a moist and unstable enough atmosphere to sustain showers and even some isolated thunderstorms. If this front does indeed stall, it would serve as a lifting mechanism for the development of showers and storms. But, as always, we will have to wait and see how this entire situation evolves over time and through further model runs.
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252. beell
NWS Hurricane Ike Wind Analysis Jan 16th, 2009
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cchs but the thing is will the front dry up or not by the time that it gets to all of us in south florida.
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When ever I have discussions about this winter just about ending--there is consistent agreement that this has been a tough winter in the northwest of Washington.

Mid December--Artic outflow and lots of snow, frozen ground,soils, river and creeks. Followed very quickly with a Pineapple Express--copious amount of warm rain and elevated freezing level. Combined with snow melt below 8,000 feet flooding occurred. Then over 20 days of fog. More snow is late Feb and and again a smattering of snow last Monday.

This has been a tough winter and I am heartily glad it is just about over.

This was not a typical winter though elements of it are not uncommon. Just too much of the combined event. It may be a piece of the changing weather scenario. However I am aware that forecast models consistently show my area to be at normal weather events--whatever normal may be!

Puddled in the pacfic northwest
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See that many people have become concerned about the drought situation in Florida, especially Southern Florida. Well, the 12Z GFS paints a nice picture for Southern Florida showing decent rainfall this coming week. Just hoping this does come true since we need the relief.


Figure 1 12Z GFS Forecast Rainfall Next Five Days (Source: Raleigh Weather)

EDIT: Just checked all the other models and it seems they're all in agreement that all South Florida will receive some needed rainfall come Wednesday through Saturday.
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NASA YOUtube page
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246. hahaguy 3:07 PM EDT on March 15, 2009

What I find interesting about that graphic is that so many of the pink counties are ones that used to be almost completely underwater 100 years ago (I mean Everglades type swamp, lots of streams, FL style rivers, and shallow lakes).
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A few more counties are gonna start turning pink soon.
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Building a blog is hard work. Thing I'm gonna work a little more on it for today. Surf mom, you get my comment about lady in red yesterday? Hope that front holds together we could use some of that rain.
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GO SPACE SHUTTLE DISCOVERY!
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Much Needed Showers



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Come see my Blog! I need sugestions on how to improve it... ;D

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hurricane season is rapidly approaching - many of us are on her map for target practice, or Hurricane pinball - as my son likes to call it--

By supporting Portlight.org you are assisting an effective grassroots organization (by the people for the people) that directs aid directly to those in need. Be part of making a difference.

If you can not attend an event - pick a blog buddy and support their efforts, no blog buddy pick a city you like and send a donation.

Are you a surfer that gets rides from Hurricane created waves? -- pay up...cause most always our pleasure has has caused havoc somewhere else...... help makes those waves guilt free
Destin Dog Walk April 26th - Check SUGARSAND,PORTLIGHT OR CODE1 Blog for details & pictures

ALSO - any folks from Houston on the blog today--check out SMMCDAVID's blog for information regarding the Portlight.org walk there.

Hurricane season approaches -- part of being prepared is supporting this WU grassroots organization that may be offering YOU hurricane aid this season.

Yikes.... and how could forget Portlight Relief Walk in New Orleans!!!!! Check out Patraps blog for details!
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Surfmom
Fantastic - glad you enjoyed the tea and hope Mother-From-The-North enjoys hers. If I remember right, tea plants are related to camelias, which do right well here as our winter flora.
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When Siesta was evac'd for Charlie... the surfers and kayakers paddled across the intracoastal from the mainland.........
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oh so that is Tony - new one for me!!
KEH - I got the tea from your local Tea Plantation in Charleston OMG -- there is nothing like it..... it's going to make Mother-from-the-North very happy. Never realized that your weather was appropriate for growing tea.
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I'm ready for this shuttle, provided my two & four leggeds at home cooperate... never really made an effort to check it out.... then I stumbled on LowerCals blog and I looking at all kinds of things up there.....

Thankfully MenInDresses are not something that will come into sight. PressLord, Orca's so horrified at the thought of a repeat performance he's whaleing (pun intended) on his blog.

Pangean - Lighten UP
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234. lhwhelk
Thanks, I am liking my 'hurricane shelf' quite a bit more now. Dr. Masters blog is great for sharing ideas, is it not? I am truly glad that I brought up my disgust of canned veggies to the blog.

235. SevereHurricane - Yep same problem here on some of the islands after Hugo. Folks had to sneak back in by boat. And during the next evacuation, folks were not so willing to leave their properties. A real problem.
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What worries me is the amount of peoeple that might stay this time in JP. After Gustav everyone was Pi$$ed at our Parish Dictator Aaron Broussard(again) because he kept everyone out of his kingdom of Jeffersonainium too long. Even the Governor Bobby Jindal was annoyed with him becuase of what he did this time.Alot more people are going to want to stay this time around.
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PROVENDER PREPARATION

Some simple things to do:
Open a can of cream-style corn. Sprinkle Bac-os. Eat.
Combine one can french-cut green beans and one can cream-style corn. Sprinkle with canned French-fried onion rings.
Any canned pasta mixed with canned zucchini and tomatoes. Sprinkle with Parmesan.
And if you want to know why you should really evacuate, read this from the Houston Chronicle, 6 months after Ike: http://www.chron.com/disp/story.mpl/metropolitan/6311751.html
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Quoting KEHCharleston:
229. SevereHurricane
What sort of preparations for your boat, do you think will be necessary?


Idk all the details, my father sure knows.
He had things that would not allow it to flip and im sure we would have some water/food of somesort in the boat. We used to have a camp in the marsh just SW of Venice,La that was built the winter right after Betsy in 1965 and Katrina completly destroyed it in 2005.But he knows lots about boats(I don't lol).

Look all we have to do is get to the JP/ST.C. line by the interstate and were out of the water.
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231. bappit
Thanks
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You can try Sazon Goya on your veggies, too. Essential ingredient to many CASI chili recipes.
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229. SevereHurricane
What sort of preparations for your boat, do you think will be necessary?
Member Since: August 19, 2008 Posts: 6 Comments: 2490
Quoting atmoaggie:


That guy lives west of NOLA...in Kenner. He will not get a 30 foot fast surge like a true coastal area, but could get a 10 foot slow surge from Lake Pontchartrain...much like parts of NOLA after Katrina.

Addendum: I have to agree with Pat, though. If under a mandatory evac...

Although, my family went into the mandatory evac zone for St Tammany to ride out Gustav in my office. But that was a special. The place is hardened like a cold-war bunker (because it was) and we were providing weather updates to the National Guard in St Bernard.


Exactly!
Its somewhat different here. The water does not come up 30 feet and then drop back into the ocean. Here were are flat and the only 2 ways we would have catastrophic flooding is...

LakeView Scenario for Metairie/Kenner: Another powerful Hurricane passes to our east and the St.Charles/Jefferson Parish levee breaches and we have a slow water rise to 10-15 ft.

Worst Case Scenario(IMO): A slow moving Catagory 4 or 5 passes just to the west of JP putting us in the RFQ and piling up a massive surge in L.P. meanwhile there is a 30 ft. Storm Surge in the WB that crosses over the MS River into the Eastbank and ultimatly causes a complete levee failure of about all levees surrounding the area while the Cat4/5 winds are occuring. Thats my worst Case Scenario.
(There are many other things that could go wrong)

Im not sure if I would ride the next bad one out at my Dads house in Metairie or Moms House in Kenner.

The point is I have put lots and lots of thought into what could happen. The most imortant thing is to BE PREPARED for the worst. I can't stress that enough!
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The only thing close to Huron that I could find -- Link

I cant imagine this was the only time it happened.
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The Spice's must FLow..LOL

The Lake Huron Cyclone 96'


An intense cutoff low developed over the Great Lakes during the period 11-15 September 1996. As the low deepened, height falls in the lower troposphere exceeded those at upper levels, the cold core low evolved into a warm core system, and vertical wind (speed and directional) shear decreased dramatically.

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Quoting Patrap:







Another essential for the kit on my end is the below. It can make dirt taste good.

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Quoting atmoaggie:


LOL...on a couple of levels...


Yep, keepin the day job.

On another note:

I was asked by someone doing a paper on Hurrican Huron if that had ever happened before. I did not know the answer.

So I ask, did we ever see anything like Hurricane Huron happen anywhere else in the world? ยง
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Quoting KEHCharleston:
atmoaggie

201. What's a Tony??
.





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atmoaggie

201. What's a Tony??

221. Since I am a bit height challenged, I have to admit, that I am uncomfortable with anything more than about 4 feet of water. ;)

There are always some exceptions and it sounds as if your circumstances was a bit different, atmoaggie.

For the rest of us, I know that it is tempting to stay, thinking you might minimize damage to your property and since authorities are sometimes slow in allowing folks back to their property.

However, Mandatory Evacuation means just like that. You do not want to hear what I think of folks who do not heed that warning. At the very least they have caused great concern and worry to their families and possibly impaired relief efforts. Worse is when they put others at risk. And of course there is that death factor - what a stupid way to die.
Member Since: August 19, 2008 Posts: 6 Comments: 2490
Wow. We hit 3"/hour rainfall rate at one point yesterday (that will well kill any lingering forest fire chances):

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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.