Derecho - June 29 (more later?) - large areas

[CrazyC83]

2.4 million or so without power now. This is going to be historic.

I'd make a Wikipedia article, but I don't know where to begin...

[vbhoutex]

This is a copy of an SPC photo of the Derecho as it progressed SW.

[CrazyC83]

We might do this all over again tomorrow. No change in the setup.

[Cyclenall]

2.4 million or so without power now. This is going to be historic.

I'd make a Wikipedia article, but I don't know where to begin...

Quoting someone from the April 27, 2011 Tornado Outbreak Thread, hurricane-like numbers. I would also guess this is the most amount of people in America without power since perhaps Hurricane Irene or even April 27, 2011? That derecho is probably one of the worst I've ever tracked if not the worst.

Your problem with Wikipedia is my problem as well regarding some of these heatwave events that have and will be unfolding...

At least one person has died from the event, which sadly is not surprising to me.

[tomboudreau]

I'm not sure how juiced the atmosphere is this morning but from what I'm feeling, sitting on the back porch, is that there is some energy in the atmosphere. Its not as oppressively humid as it was yesterday, but there is this sense that things could turn ugly today. There are more higher clouds today then yesterday. There is a light breeze blowing. The first thing I did notice this morning, stepping out of the door, is the smell of smoke however. We could smell smoke two nights ago, but we attributed to a pretty big fire closer to Pittsburgh. I know of no such fire today, so I am going to guess the smell we have today is from the fires out west.

[WeatherGuesser]

This is a copy of an SPC photo of the Derecho as it progressed SW.

Original source page?

[tomboudreau]

This is a copy of an SPC photo of the Derecho as it progressed SW.

Original source page?

It was on the SPC Facebook page.

[RL3AO]

Derechos are such fascinating weather systems. I will also argue that the overuse of severe thunderstorm warnings for weak supercells/multicells causes too many people to ignore SVRs when they are really needed for derechos.

[CrazyC83]

For high-end events, they should issue Extreme Wind Warnings - perhaps if the wind gusts are 90 or 100 mph or higher.

[Stephanie]

That derecho that was approaching Baltimore and DC late last night at around 10:30 got to me at around midnight. Second night of severe weather. I have a friend in the next town that was without power for at least 7 hours.

It looks like OH really was sucker punched though. They said for yesterday in the morning just a chance for a thunderstorm and the bigger chance would be today and I'd hate to see what today may bring! Wow!

[CrazyC83]

That derecho that was approaching Baltimore and DC late last night at around 10:30 got to me at around midnight. Second night of severe weather. I have a friend in the next town that was without power for at least 7 hours.

It looks like OH really was sucker punched though. They said for yesterday in the morning just a chance for a thunderstorm and the bigger chance would be today and I'd hate to see what today may bring! Wow!

It seems the hardest hit areas were central-western Ohio and the Baltimore-DC region. It seemed to weaken a bit over the mountains but reintensify over the Piedmont.

Yes, the threat is there again...best to hope it doesn't happen. A repeat on the same track would mean double misery and more damage, while a different track would double the number of people in trouble.

[tomboudreau]

Sitting at 11:38 AM - the temp is only at 77.9 outside compared to well into the 90's yesterday. We have a lot of cloud cover right now, so I'm really hoping that the action today doesn't get going. The clouds have helped greatly today.

[CrazyC83]

The SPC had only a See Text at 06Z in most of the area hard hit yesterday.

In their defence, however, derechos are notoriously hard to predict, and I would have been conservative too. They almost always require playing catchup. The Moderate Risk at 20Z and 01Z were well-forecast (a High Risk would have verified, but that is too bold for most).

Had I been the SPC, I would have gone 15-hatched initially (low confidence but high impact potential), and worked from there. I would have done the same today; I believe 30% might be too much for an initial forecast.

[CrazyC83]

AccuWeather calling it a Super Derecho...

Not sure if that is a good term here. This was just an ordinary classic derecho, hitting heavily populated areas. They are ALWAYS going to be extremely dangerous. There are many other cases of long-lived derechos, mainly in the Midwest.

[CrazyC83]

http://en.wikipedia.org/wiki/June_2012_ ... st_derecho

Starting it up now.

[CrazyC83]

Article now published

[somethingfunny]

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Based on current temperature and satellite observations, I put together this map showing where I think a derecho would track if one develops today.





As for the official forecast...

[CrazyC83]

I'm in agreement - if it forms, it would be in the central Appalachians, and tracking roughly along I-64. Major cities at risk: Louisville, Cincinnati, Lexington, Knoxville, Tri-Cities TN-VA, Charleston WV, Washington, Richmond, Roanoke, Hampton Roads, Greensboro-Winston Salem, Raleigh-Durham.

[CrazyC83]

Still, I wouldn't put up a Moderate Risk yet - maybe at 0100Z.

[CrazyC83]

Down to 15%, no longer hatched. Derecho unlikely? I'd have at least kept it hatched in the corridor mentioned. Agreed the area that was pounded last night should be lowered, but south of there in the unaffected air mass...

SPC AC 301950

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT SAT JUN 30 2012

VALID 302000Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL IL/IND EWD INTO THE
NC/VA COAST....

...THERE IS A SLGT RISK OF SVR TSTMS FROM NRN KS INTO THE DAKOTAS...

...OH VALLEY INTO THE MID ATLANTIC...
REDUCED SEVERE PROBABILITIES TO A BROAD 15% MINIMAL SLIGHT FOR THE
REGION. THE AIR MASS OVER MUCH OF THE AREA FROM PA INTO ERN VA...MD
AND DE HAS NOT YET RECOVERED FROM THE PREVIOUS MCS. THE 18Z IAD
SOUNDING HAD VERY LITTLE INSTABILITY...ALTHOUGH MIDLEVEL FLOW WAS
STRONG. STRONGER HEATING WAS OCCURRING JUST SW OF THE AREA OVER
CNTRL VA...AND CU WAS INCREASING NEAR AN OLD BOUNDARY FROM ERN KY
INTO WRN VA. IF STORMS FORM HERE...THEY COULD GROW UPSCALE ACROSS
SRN VA...ERN TN AND NRN/WRN NC.

OTHER STORMS WERE LINGERING OVER CNTRL IL INTO IND...AND MAY
EVENTUALLY GROW UPSCALE AS STRONG INSTABILITY REMAINS OVER THE
REGION.

...SRN APPALACHIANS...
EXTREMELY HOT TEMPERATURES HAVE MIXED MOISTURE VERTICALLY AND ALSO
REDUCED CAPPING. VISIBLE IMAGERY SHOWS CU ALONG AND S OF THE OLD
OUTFLOW BOUNDARY FROM ERN KY INTO WRN VA...AND ALSO SWD ACROSS ERN
TN...WRN NC...AND NRN GA. WITH CONTINUED HEATING...ISOLATED STORMS
WILL BE POSSIBLE. LOW TO MIDLEVEL LAPSE RATES ARE VERY STEEP...AND
WITH WEAK WINDS ALOFT...THIS WOULD SUPPORT VERY STRONG BUT LIKELY
SHORT LIVED UPDRAFTS CAPABLE OF DAMAGING DOWNBURSTS AND MARGINAL
HAIL.

...WRN NEB/NERN CO...
SHUNTED WRN EDGE OF SLIGHT RISK EWD TO ACCOUNT FOR DRYING FROM THE
W.

..JEWELL.. 06/30/2012