Hottest July on record reported nationally; fairly strong cold front about to give summer a punch in gut, trigger storms Friday
The National Oceanic and Atmospheric Administration reported Wednesday that July has set the record for the hottest month on record in the U.S. (dating to 1895) based on average temperature over the contiguous 48 states (that is, all but Alaska and Hawaii), surpassing by two tenths of a degree July 1936. Interestingly, while several states reported a July that was among the 10 hottest on record, Virginia was the only state recording its hottest July on record, according to the National Climatic Data Center. A week ago, I wrote about how July was Roanoke’s hottest July on record, and second hottest month, dating to 1912, primarily driven by warm nighttime temperatures. How much, or how little, man-induced global warming has had an impact on this specific situation is a (pardon the all-too-obvious pun) hot topic in climatological/meteorological circles, with answers ranging from it being the primary cause, to an exacerbating factor, to a minimal component, to no effect at all above natural variation. Various studies in the academic world will be sorting that out over time. The short- term purely meteorological cause of the heat and drought, undoubtedly, has been a persistent area of high pressure primarily over the central U.S., expanding eastward at times. (It is important to note that while Virginia was the only state to have its hottest July on record, that doesn’t mean Virginia’s temperatures were hotter than states to our west that have hotter normal summer temperatures than we do). The question now is how long this “heat dome” will persist, or possibly how often it will return, into the remainder of summer and perhaps fall.
It looks certain that the heat dome will take a major body blow over the next 72 hours as a strong cold front is driven southward and eastward from Canada, almost reaching the Gulf Coast by Sunday. The punch of relatively cool, dry air into hot, humid air will fire thunderstorms, some of which may be severe, with damaging winds as the main threat. Those storms will be more likely in the Ohio Valley on Thursday, and then perhaps in the Appalachians and Mid-Atlantic come Friday. While Saturday will cool off to the 70s/low 80s for highs and 50s/low 60s for lows (perhaps coolest on Sunday morning, actually) across Southwest Virginia, our cool shot may be relatively short-lived, with temperatures beginning to rebound back to more summerlike levels by early next week. But make no mistake that in the bigger picture, this cold front is deflating the heat dome quite a bit, and there may be even more cool air pooling in Canada, perhaps even extending into the Great Lakes region. It’s not really the first hint of fall, but it is an indication that the big, bad heat wave of 2012 is not invincible.
Before the front arrives — Thursday will not really be a “heat wave” kinda day in Southwest Virginia, but it will be rather hot with highs in the mid 80s to low 90s over much of our region, and the typical scattered afternoon thunderstorms boiling up in the humidity.
August 8, 2012 - 11:34 PM
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50′s in August? Puhleese.
How widespread do you think the storms will be on Friday evening – pulse pop-ups or long areas of MCS storms? I’m thinking about camping that evening. The last time I went camping was June 29 :/
What does the 118 mean in Va.? I missed that one somewhere.
They just put us in the dry hole for this cold front Friday, bummer.
http://www.hpc.ncep.noaa.gov/qpf/p120i12.gif
WD: The “118″ means that out of 118 years on record, 1 would be the coldest July and 118 would be the hottest.
Icithus: Definitely will be MCS storms. Afternoon to early evening would be highest risk of storms, likely moving out by late evening. Saturday looks ideal for outdoor activities, though.
Rick: Yep, that’s my suspicion about this. A Blue Ridge jumper, with strongest storms to west overnight and in the Piedmont to coast on Friday. But there is enough of a severe risk to be watchful.
Art: Blacksburg’s normal low for this time in August is 60 degrees — so lows in the 50s aren’t that unusual for areas west of Roanoke. Even Roanoke had 3 lows in the 50s last August, which averaged nearly 3 degrees above normal. But, of course, we tend to see lows that cool more toward late August rather than early August.
Another foggy morning out here in my valley! That makes 4 (I think). It was beautiful this morning though, nice cool breezes coming in the open windows and doors as I made some bread. Looking forward to some temps in the 50s overnight!
Joe – re: comment about the Doppler from yesterday’s blog. Yes, I do remember when they used Volens and I think I remember Robin Reed talking about the “new” Doppler that was going up. One of my former students told me once about the Doppler being near his back yard and that he had walked over to it. I checked the elevation around the Doppler and it is at 2870 ft. Our new name for the Doppler is the Double D or the Doppler Deflector because of all the storms that go around it.
Kevin, had to laugh this morning because when I told the Man of the House that it was going to rain tomorrow, he wanted to know what time it would start. I told him you couldn’t give an exact time. Of course I told him that the rain would go around us anyway and not to worry he could still work in the garden. I like the name for the storms – calling them “Blue Ridge Jumpers”.
Tina – foggy up here on the ridge this am too. Was nice to look out and see the fog in the valleys with the tops of some of the mountains sticking up through the fog.
Up on that mountain back in those trees
is the magic white orb WSR-88D.
Since Roanoke records only go back to 1912, where does the “118 years on record” come from?
lots of good rain from Atlanta
to west of Knoxville,,,
NWS so far doesnt have it getting
as far as GSO or ROA…
only a mention briefly in Bristol Forecast..
one 35000 footer near Boone,,
I think its gonna get a bit closer than NWS
shows so far…im thinking at least thunder vicinity.
Its a slow system so far for sure.
WD: Not just Roanoke, but state of Virginia as a whole. Records for some sites like Richmond and Lynchburg do go back that far or even farther. NOAA considers 1895 the first year with reasonably reliable records to calculate state averages. Certainly the data set is far from perfect.
That Boone cell is sneaking across the Grayson line..
topping ou tnow at 40k feet
I got a rare, WONDERFUL surprise this morning. Reported for work a bit before 7 AM (today was supposed to be my “non-scheduled” day, but I was told to report because we are SO short-handed), and the boss said, “I have great news for you, Doug. Another branch sent us one of their letter carriers, so we don’t need you now. Enjoy your day off.” Which I did. DVGC, of course. Some isolated fog in spots, one near (west of) C-burg, and another just west of the New River, but not at the Claytor Lake area, surprisingly. Nice weather.
I just checked on TWC’s hourly forecast for Roanoke, and got a big surprise. A pleasant one, too, IF IT VERIFIES. 3PM and 4 PM .. 10% chance of rain (POP). 5 PM: 50%!! 6 PM: 95%!! 7PM and 8PM: 100%!!! Frankly, my dears, I think this is “Beautiful Dreamer” stuff, but I would love it if we got a big t-storm here. I rolled the dice and the lawn just got mowed this AM, so I am really counting on getting 1/2 inch of rain by tomorrow night. With luck our yard could look some semblance of normal by the weekend. Today was only the 2nd time the lawn has been mowed since June 30.
The POP pops back and forth between 30% and 40% from 9 PM tonight through noon Friday, then starts jumping higher again to 50% and 60%. If I get missed completely or only get 2/10ths or less, be forewarned. You folks are going to need several mops and perhaps even hip boots, because I am going to do a lot of crying …… :>) :>)
I’m interested to see how much of that Tennessee/eastern Kentucky rain/storms area works in here later.
NWS has no mention of rain till noon tomorrow for ROA.
TAF KROA 091740Z 0918/1018 20005KT P6SM FEW040 BKN250
FM100000 19005KT P6SM OVC250
FM100900 17003KT 5SM BR BKN080
FM101300 21004KT P6SM FEW040 OVC250
FM101700 26005KT P6SM VCTS OVC050CB=
Is radar showing an outbreak of supercells in Tennessee?
Not supercells. A big area or heavy rain and storms. A couple of severe thunderstorm warnings out, no watches, mostly heavy rain.
Dew point has actually dropped 2F in the last hour Roanoke..
as has Blacksburg,,,
Drawing in fairly dry air.
actually dropped 4F for BCB
SHEESH,,,make that 6F drop for the Burg.
Have been outside most of the day and just came in and looked at the radar – Oh My Goodness! Looking back towards Kentucky and Tennessee – I think it will be here tonight. All ready for my “0.03″ inches that generally comes with this type of storm. Hopefully we will get some of that moisture up here on the ridge.
I agree with Kevin’s comment at 3:04 this afternoon.
I hope that big cluster on the radar makes it here. We’re going to lose heating of the day and it has mountains to cross and several miles to travel. I’m skeptical at best.
Terrible storm in max meadows! Heavy downpours and it hailed for over five minutes with hail the size of ping pong balls. Kinda cool to see when your safely inside but I’m glad I wasn’t on the road.
Thanks for answering my sack full of questions. You know it’s going somewhere, just not where yet.
Kevin,
Will the line of storms heading NE through SW Va. tonight have any impact on tomorrow’s storms?
Definitely. How, though, is uncertain. It can leave behind outflow boundaries and more surface moisture that enhance storms. Or it could leave behind debris cloudiness that limit warming and instability. This is why storms remain such a “mesoscale” thing to forecast, only in a limited area within a few hours, because we can’t know til tomorrow sometime exactly how the factors will line up.