northwest flow environment

[Bill Hark]

Does anyone have a idealized picture of a supercell in a northwest flow environment? This is a situation I am not as experienced in chasing, and I have been having trouble finding good info.

Bill Hark
http://www.harkphoto.com

 

[Marcus Opitz]

The only thing I can tell is that it is more common during the summer months. I have seen a few nasty storms occur in June, July in MO.

 

[Michael P. Morris]

IIRC, the large solitary supercell that passed through Central Illinois late last summer (date eludes me) occured in NW flow. That had some amazing structure, both on radar and from the pictures I have seen.

 

[Jeff Snyder]

Originally posted by Bill Hark
Does anyone have a idealized picture of a supercell in a northwest flow environment? This is a situation I am not as experienced in chasing, and I have been having trouble finding good info.

Bill Hark
http://www.harkphoto.com

Bill,

For the most part, a supercell is a supercell is a supercell. You can essentially just "turn" the soutwest-flow supercell 90 degrees clockwise, and you'll get a northwest-flow supercell. The updraft is still on the upwind (aloft) side of the storm, except that is to the northwest of the FFDR / precip core instead of the southwest side of the FFD/precip core for the northwest-flow aloft regime.

 

[joel ewing]

Hi Bill. If I remember right, the June 9th. '03 O'Neill, Nebraska F-3 monster dirty barrel was via northwest flow. As well as the F-2 Stuart, Nebraska prior to it.
There are a lot of wonderful videos of those. I've got 3 or 4 of 'em from different guys. My chase partner and cousin Doren and I were on both of 'em from the gitgo.

 

[Joe Zemek]

Originally posted by Michael P. Morris
IIRC, the large solitary supercell that passed through Central Illinois late last summer (date eludes me) occured in NW flow. That had some amazing structure, both on radar and from the pictures I have seen.

Yeah, this was in July, and hit Roanoke, I think. Did F4 damage to some industrial buildings. I remember watching it on satellite and it was heading around a ridge, moving SE, like a right mover, except that the anvil was also blowing SELY, which has interesting implications for inflow temperature modification.

 

[Michael Auker]

The storm reports map for July 13 is very striking; the map shows the evolution of a lone supercell in NW Illinois to a full--blown derecho stretching down to Alabama and Georgia. I experienced my first derecho that day. What surprised me was that the high winds lasted about 20 to 30 minutes, not at all like an ordinary severe squall-line thunderstorm.

 

[Skip Talbot]

The Plainfield IL F5 of August 1990 also occured under similar northwest upper level flow. At the weather seminar here they did a comparison of how close the Roanoke F4 of last year was to the Plainfield F5. When you have surface Td's of 80 and very cold air streaming in from the northwest you get a huge amount of instability. 5000 JKg in the Roanoke storm and 8000 JKg in the Plainfield storm IIRC.