Jake Stehli from Menomonee Falls, Wisconsin asked:
I wonder, if it is atmospherically possible to have a such a strong storm (way stronger than even the strongest synoptic system like a 1,000 year storm) that if convective snow can grow tall enough to support thunder, could it be possible t...hat given enough shear (probably would have to be very near the low pressure and 850 just cold enough to support snow all the way down) that the low topped convection spins up a land spout or very weak tornado. Now this would not be a traditional super cell with 60,000 foot tops because the troposphere in winter is not as robust. However tornado formation would essentially occur from a very low topped rotating convective thunderstorm. The only way I think, if it is possible that the tornado would form solely on extreme super upper air dynamics and not surface dew points or temperatures (around 32-33 degrees). I know it sounds absurd, but it's fun to think of the possible upper limits of atmospheric dynamics in Earths Atmosphere. I know it's the same.
Here is the answer from Dr Tim Coleman from UAH in Huntsville:
Convection in these events occurs slantwise (parcels can't rise straight up or close to it like in warm core storms), because buoyancy is what drives convection. Parcels have to move along a slant, starting south, and flow north, with just the right momentum, to stay warmer than their environment. Also, the convection is elevated (not surface based), so updrafts and downdrafts can't tilt/stretch/advect vorticity in the boundary layer (near the surface). So, a classic tornado would be difficult to get. Even a landspout, because of no vertical instability.
However, in horizontal wind shear zones (friction/topo boundaries), in a very strong surface low with high wind, you could get vorticity that would occasionally spin off a rotating column of air. We observed this one night near HSV with the ARMOR radar. A gravity wave with wind behind it crossed an isolated mountain, and a vortex spun up and moved several miles. I am working on a short paper about this event for Monthly Weather Review.
Tim C.
Dr. Timothy A. Coleman
Research Scientist
Atmospheric Science Department
The University of Alabama in Huntsville
Tel. (205) 612-4229 or (205) 661-1649
Email: coleman@nsstc.uah.edu
Web: vortex.nsstc.uah.edu/~coleman
Cool...thanks...some rather "out there" questions foster understanding real life meteorology easier. To understand how it cannot really happen, allows deeper understanding of the correct reasoning. I had a hunch that slantwise and elevated convection were the biggest culprits that would not support twisters very well. Possibly in extremely heavy snow, lightning might even be more of the result of extreme friction with ice and water vapor even with storm clouds having enough updrafts and downdrafts despite being a "True" thunderstorm. However, the real reason I came up with this left field question is that a few times in recent years, I have seen thunder snow showers that formed along a cold front in more than a typical synoptic winter storm fashion (eg slantwise). I have a few years ago encountered a marginally severe squall line on radar screaming towards southern WI. The squall line had all the characteristics of your typical spring time storms. The formation of the squall line in IL occurred in a region that was marginally conducive for vertical parcel thunderstorm development. Severe thunderstorm warnings were issued as far north as Rockford and the counties in IL that hugs the WI border. Since the squall was racing at 50 mph to the northeast, it seemed to cross into SE Wisconsin faster than it could lose all its characteristics. As the storm reached my house, the temperature was 35 degrees and you could hear the approaching thunderstorm like a spring time one opposed to a text book definition of a thunder snow event. Frequent lightning shot across the sky and it started to rain; Lots of cloud to cloud magenta bolts. As the storm was right over ahead, dynamic cooling allowed the snow in the storm to reach the ground. Even the radar had a hard time believing the storms were producing snow over head that was making it to the surface. Thunder was crashing and lightning was flashing although more muffled now because of the snow, However way more frequent than typical thunderstorm. (Remember this was the same squall line that triggered warnings for hail and wind 50 miles SW of me.) We received 2 inches of the heaviest wettest snow I have ever seen! After melting a core sample of those 2 inches, nearly 3/4" of water made up just two inches. It was like snowing slush. Perhaps the thunderstorms intensity pushed the snow down to the surface with the remaining downdrafts before it could melt? And of course did not have a camera to document this....Sincerely, Jake Stehli
ReplyDeleteCool...thanks...some rather "out there" questions foster understanding real life meteorology easier. To understand how it cannot really happen, allows deeper understanding of the correct reasoning. I had a hunch that slantwise and elevated convection were the biggest culprits that would not support twisters very well. Possibly in extremely heavy snow, lightning might even be more of the result of extreme friction with ice and water vapor even with storm clouds having enough updrafts and downdrafts despite being a "True" thunderstorm. However, the real reason I came up with this left field question is that a few times in recent years, I have seen thunder snow showers that formed along a cold front in more than a typical synoptic winter storm fashion (eg slantwise). I have a few years ago encountered a marginally severe squall line on radar screaming towards southern WI. The squall line had all the characteristics of your typical spring time storms. The formation of the squall line in IL occurred in a region that was marginally conducive for vertical parcel thunderstorm development. Severe thunderstorm warnings were issued as far north as Rockford and the counties in IL that hugs the WI border. Since the squall was racing at 50 mph to the northeast, it seemed to cross into SE Wisconsin faster than it could lose all its characteristics. As the storm reached my house, the temperature was 35 degrees and you could hear the approaching thunderstorm like a spring time one opposed to a text book definition of a thunder snow event. Frequent lightning shot across the sky and it started to rain; Lots of cloud to cloud magenta bolts. As the storm was right over ahead, dynamic cooling allowed the snow in the storm to reach the ground. Even the radar had a hard time believing the storms were producing snow over head that was making it to the surface. Thunder was crashing and lightning was flashing although more muffled now because of the snow, However way more frequent than typical thunderstorm. (Remember this was the same squall line that triggered warnings for hail and wind 50 miles SW of me.) We received 2 inches of the heaviest wettest snow I have ever seen! After melting a core sample of those 2 inches, nearly 3/4" of water made up just two inches. It was like snowing slush. Perhaps the thunderstorms intensity pushed the snow down to the surface with the remaining downdrafts before it could melt?
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