Never-ending severe weather - April 18 and 19

[CrazyC83]

With a possible reprieve in store tomorrow, it seems the severe storms and tornadoes want to keep firing up again like it is a mean conveyor belt. Yet another round of severe weather is expected Tuesday and Wednesday in the Midwest.

Key question - if it forms, should it be a separate outbreak (with the one-day break) or part of the same sequence? The last time there was a one-day break in an outbreak (March 10), I considered it part of the same outbreak sequence. It is also part of the same air mass.

Also, I think this Tuesday and Wednesday will rival April 2 and 7, not the steady, slowly accumulating tornado counts of this weekend.

[Gorky]

If it is a separate low pressure system, I'd clasify it as a separate outbreak. To me an outbreak is 30+ tornados in one day anyway. 10-20 in one day really isn't out of the ordinary when 1800 tornados a year is easily doable... I'd only call 3 of this years events outbreaks to be honest....

[CrazyC83]

I don't take into account events over one day or multiple days. For example, last week (April 6-8) was a 3-day outbreak.

In my view, a major outbreak is 50+ tornadoes, or 25+ with a killer tornado. (The first criteria is seldom reached on its own outside of tropical storms or hurricanes)

[wxmann_91]

I have a definition of an outbreak which I use, but IMO March 9, March 11, March 12-13, April 1-2, and April 6-7 were separate outbreaks. One storm system that spawns two days of svr I would count as one outbreak.

Anyway, with the NAM on crack, Wednesday and Tuesday is an extremely challenging forecast, one in which I will not dive deep into. But unidirectional shear and moisture/instability I believe scream squall line. LLJ is nonexistant as well. All in all I expect little from this upcoming system attm except a major pattern change favoring cold in the east as well as a powerful snowstorm in the Northern Plains.

[conestogo_flood]

In my view, a major outbreak is 50+ tornadoes, or 25+ with a killer tornado. (The first criteria is seldom reached on its own outside of tropical storms or hurricanes)

How come you classify a killer tornado as a tornado outbreak. Any tornado can kill someone. I'd say the number of deaths wouldn't matter, unless it is something significant like over 5. A tornado outbreak generally means a "outbreak" of many tornadoes.

[summer_chick]

I would like some rain, but I don't want any tornadoes thank you very much.

[Gorky]

Another thing about an outbreak is it has to consist of many tornadic supercells in my opinion. If you get a marginal day when one storm goes tornadic, and struggles to hold a decent tornado on the ground for any amount of time, but you end up with 20 reports of the f0-f1 variety, I'd think that was much less impressive than if you had 5 cells all dropping monster long track tornadoes, but only 10 total. For that reason you cannot classify something as an outbreak based purely on numbers. It should be based on strengths of tornados, coverage of tornadoes (how widespread), and the numbers of tornadic cells. It would be great if there was some sort of measure similar to the ACE index for hurricane seasons to compare outbreaks. In fact I could have sworn I'd read a paper about such a thing for tornado outbreaks a few years back but can't find anything with google. The difficulty with this is obviously, we often only get the final maximum intensity of a tornado, and not a breakdown of the tornadoes damage for every inch of its path, so that does not work quite so well....

[wxmann_91]

OK here's my definition:

At least 10-15 tornadoes CONFIRMED in ONE DAY

If it's two day event and one day has 200 tornadoes and the other has 5, only the first day is counted as an outbreak of tornadoes. Svr wx outbreak IMO is at least 100 reports, or if it's a tornado outbreak it automatically counts as a svr wx outbreak.

Doesn't matter if it's from one or 500 supercells, doesn't matter if 0 or 500 people are killed, and doesn't matter whether they're all F0's or F5's.

[CrazyC83]

Moderate Risk issued. 15% and hatched for tornadoes.

[CentralMO-TVwx]

This event, although very localized has me very concerned. Many different things coming together for the possibility of some strong tornadoes here in central MO. NAM forecast soundings have some incredible instability (up to 4000 CAPE), shear (90 kts), a perfect hodograph, high helicity values (near 400), and a couple of other good indices. Moisture is streaming northward very quickly (mid 60 dewpoints across southern Missouri) as well so that should not be a problem.

If we don't warm up to our full potential today, that WILL limit the instability some, BUT it would also allow for dewpoint depressions to be less creating a somewhat favorable environment for tornadoes.

With the warm front and low nearby, I think we're setting the stage for some intense weather here in central MO.

[CrazyC83]

This event, although very localized has me very concerned. Many different things coming together for the possibility of some strong tornadoes here in central MO. NAM forecast soundings have some incredible instability (up to 4000 CAPE), shear (90 kts), a perfect hodograph, high helicity values (near 400), and a couple of other good indices. Moisture is streaming northward very quickly (mid 60 dewpoints across southern Missouri) as well so that should not be a problem.

If we don't warm up to our full potential today, that WILL limit the instability some, BUT it would also allow for dewpoint depressions to be less creating a somewhat favorable environment for tornadoes.

With the warm front and low nearby, I think we're setting the stage for some intense weather here in central MO.

That's my thought. This won't be a tornado swarm like March 12 or April 2 or 7, but it could be locally severe. Strong and even violent tornadoes are possible if everything falls in place.

[CrazyC83]

Here is my prediction map for today. NOT AN OFFICIAL FORECAST.

[jkt21787]

The hatching for tornades was removed. Good move by SPC. Deep layer shear and mid level flow is lacking. Instability and some higher low level shear/favorable hodographs should compensate a bit, but I think there won't be more than one or two strong tornadoes should any occur, thus making hatching unnecessary.

[dean]

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 199
NWS STORM PREDICTION CENTER NORMAN OK
335 PM CDT TUE APR 18 2006

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

NORTHERN AND CENTRAL MISSOURI

EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 335 PM UNTIL
1100 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES NORTH OF CHILLICOTHE
MISSOURI TO 20 MILES SOUTHWEST OF FORT LEONARD WOOD MISSOURI.
FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH
OUTLINE UPDATE (WOUS64 KWNS WOU9).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...THUNDERSTORMS ARE EXPECTED TO DEVELOP DURING THE NEXT
1-2 HOURS NEAR A SURFACE LOW CURRENTLY OVER MCI AND ALONG A DRY LINE
EXTENDING SWD ACROSS WRN MO. AIR MASS IS VERY UNSTABLE...ESPECIALLY
INTO CENTRAL MO SOUTH OF A WARM FRONT NOW EXTENDING FROM NEAR STL TO
MCI. BOTH SHEAR AND LARGE SCALE ASCENT WILL INCREASE THROUGH THE
EVENING AND ENHANCE THE RISK OF SEVERE THUNDERSTORMS...INCLUDING
TORNADIC SUPERCELLS...WITH DEVELOPMENT SPREADING ENEWD THIS EVENING.
TORNADO THREAT WILL BE HIGHEST NEAR THE LOW CENTER AND WARM FRONT
WHERE LOW LEVEL SHEAR WILL BE MAXIMIZED. VERY LARGE HAIL AND
DAMAGING WINDS WILL BE ADDITIONAL HAZARDS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 24020.


...EVANS

[CrazyC83]

Looks like we are going nocturnal once again...is it just me or are most of these tornadoes this year all happening at night???

[simplykristi]

Funnel cloud about 5 miles west of Chillicothe MO. Baseball-sized hail reported with this storm.

Kristi

[simplykristi]

Tornado on the ground... According to a ham operator report, there is damage in Chillicothe MO.

Kristi

[CrazyC83]

Yep, they seem to have fired up abruptly...

[breeze]

Aw, crikies - here we go, again!

[CrazyC83]

3 tornadoes (plus 1 possible one in the wind section)