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Severe weather thread number ...I think X ?


Typhoon Tip

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The term has been tossed around quite a bit since the DC event, and the East Coast public is really just starting to hear and recognize the word because of it. I think part of why he may be saying it is because people understand that it means big wind is possible tomorrow.

The definition really is that it is producing nearly continuous wind or wind damage for over 240 miles. Not scattered severe wind, or taking a brief break before reorganizing.

It's odd though..If he mentioned it was possible in the afternoon/evening..that would make much more sense..but for a derecho to occur on the cool side of the warm front initially seems almost impossible

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The term has been tossed around quite a bit since the DC event, and the East Coast public is really just starting to hear and recognize the word because of it. I think part of why he may be saying it is because people understand that it means big wind is possible tomorrow.

The definition really is that it is producing nearly continuous wind or wind damage for over 240 miles. Not scattered severe wind, or taking a brief break before reorganizing.

Yeah I think something afternoon/evening is possible... but down here I'm not expecting severe convection prior to 18z.

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It's odd though..If he mentioned it was possible in the afternoon/evening..that would make much more sense..but for a derecho to occur on the cool side of the warm front initially seems almost impossible

Right, without the environment already in place, the only way parts of the Northeast get in on a derecho tomorrow morning is a couple wind reports on the dying end of a Midwestern event.

A long lived decaying MCS does not equal derecho, but it's fun to say.

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18z NAM bumped the WF a little northeast. Tongue of high surface theta-e punching into western CT. But the strongest SRH is now displaced further east/north with the front. Instability and shear seem a little more out of phase

Looks to me like the same areas in CT are looking at problems on teh 18z NAM. Expecting locally backed winds to enhance SRH across a portion of the Hudson Valley east toward HFD.

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BOX disco not quite as good as ALB's breakdown was

SINCE MODELS KEEP PUSHING THE SYSTEM

NORTHWARD...REGIONS DOWN SOUTH INCLUDING CT/RI AND WESTERN MASS

WILL SIT IN A HIGHLY UNSTABLE AIRMASS. MLCAPES ARE BETWEEN

1500-2500 J/KG AND 0-6KM BULK SHEAR RANGES FROM 40-50 KTS...GOOD

INSTABILITY AND DEEP LAYER SHEAR WILL ALLOW FOR STRONG TO SEVERE

STORMS TO DEVELOP. AS WARM FRONT LIFTS NORTHWARD IN THE LATE

AFTERNOON EXPECT STORMS TO DEVELOP...AROUND 3-5PM. THESE STORMS

MAY BE ISOLATED IN NATURE AT FIRST PRODUCING LARGE HAIL AND

DAMAGING WINDS...EVEN AN ISOLATED TORNADO CAN NOT BE RULED OUT.

AGAIN THE BEST REGIONS WILL BE ACROSS CT/WESTERN RI AND WESTERN

MASS...SOUTH OF THE PIKE...WHERE THE BEST CLEARING WILL OCCUR. STORMS

WILL CONTINUE THROUGH THE LATE AFTERNOON AND INTO THE EVENING

HOURS. AS THE DAY GOES BY EXPECT A FEW BOWING SEGMENTS AS WELL

WITH DAMAGING WINDS BEING THE MAIN THREAT. LAST THREAT IS FLASH

FLOODING AS PWAT VALUES DO REACH ABOVE 2 INCHES. DUE TO NUMEROUS

NATURE...CANNOT RULE OUT TRAINING ALONG STORMS.

OVERNIGHT THURSDAY...

CONVECTION WILL CONTINUE INTO THE EVENING AND OVERNIGHT HOURS AS

LLJ INCREASES ACROSS THE AREA COMBINED WITH THE HIGHLY UNSTABLE

ENVIRONMENT. EXPECT THE THREAT WILL TRANSITION TO STRONG DAMAGING

WINDS DURING THE OVERNIGHT HOURS. STILL UNCERTAIN ON EXACT

LOCATION BUT BELIEVE STORMS WILL BE WIDE SPREAD AND QUITE

NUMEROUS ACROSS THE REGION...ESP SOUTH OF THE PIKE. FLASH FLOODING

THREAT WILL REMAIN INTO THE OVERNIGHT HOURS AS WELL

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mod risk... 45% hatched from CT Valley points west.

You need to include a northern border on your description as the river heads up to Canada. :)

Wow mod risk for all. This is what we live for. Wx extremes

Risk for all; fun for some.

I guess if the greatest Severe Threat is CT River valley west, then what can we expect east of the river??

Blizz will double his .04" from this week.

Seriously though--looks like some good times for folks in the SW zones! Not sold on anything further north. If nothing else, some more rain will be nice.

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Just want to clarify something... With a mid/u/a speed max rolling through the flow along and N of the warm boundary overnight there could just a likely evolve a general zone of isentropic lift related rains with embedded elevated convection. That would much less related to derechio kinematics. Derechios tend to develop and then cross into warm sectors to the right. Typically the day preceding them is hot/torrid already. This different than that.

When I reached that part in bold...I knew it was a Tip post...

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You have no idea. AccuCrap Pro had their newsfeed spammed with all sorts of 'derecho' garbage.

Sent from my 4G 2

it sorta seems there is no super hard definition but accepted papers also have 3 reports of 75 mph+ as a requirement over some fairly large distance. today accu had a tweetfest showing off they don't know what one is.

it seems they and twc have made at least a semi calculated decision that "warning" is worth overstating. in a number of cases you probably need somewhat extensive post-event analysis to declare it one.. others are obviously apparent.

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re: AccuWx / TWC throwing the D word around again, let's not forget this call, July 7:

Dr. Greg Forbes@DrGregForbes

A derecho (widespread thunderstorm damaging wind event) could drive from north-central to southeast PA, NJ, MD, DE thie afternoon, evening.

Threshold for calling derecho is lower with increased public awareness/excitement after DC.

On the other hand, BUF did also mention threat of derecho early Thurs AM for western NY:

As the warm front presses northward expect a complex of

thunderstorms over lower Ontario Canada to reach wny around or just

past midnight. There is a chance that damaging wind gusts may

accompany the complex of thunderstorms. As a result...Storm Prediction Center has wny

and portions of central New York outlined within a slight chance

for severe thunderstorms. Spc's mean derecho parameter...which is

a product of dcape...MUCAPE and the 0-6 km shear continues to

place the highest potential for a derecho over southern Ontario

Canada and then advancing into portions of western New York later

overnight.

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