Wednesday, February 21, 2007
FORECAST: 2/23/07
As far as chasers are concerned, I believe Friday will be the main event. The timing of the main wave is a bit faster than previously progged. Though this will have little impact on what happens (i.e., tornadoes), it will have a large impact on where it happens. With the faster timing of the system, forcing for convection will occur sooner and wind fields will increase sooner which will increase the potential for daylight tornadoes in the Sooner state.
A few thoughts about this potential event:
First, I think the timing of the wave is particularly good, according to the latest model runs. Most significant tornado outbreaks occur when increasing flow (at all levels) is coincident with peak heating/thunderstorm initiation. This will likely be the case Friday as mid and upper level flow increases dramatically during the afternoon and evening hours.
Also, the 12Z NAM shows a narrow instability axis in place by 00z Sat (6 p.m. Fri). The maximum in CAPE is progged to be in NW OK (~1500 j/kg). On the other hand, the NAM forecasts the greatest low-level shear (0-1 km) south of I-40. Thus, the best juxtaposition of favorable parameters appears to be close to I-40. This far out, it's pointless to banter about model output on such a small scale, but it is interesting to discuss possible scenarios (based upon experience and climatology).
I think the most likely scenario (see 3/27/04) is that several storms will form along the dryline (all potentially tornadic), but the greatest threat of tornadoes will exist on the northern end of the line. Temperatures will be slightly lesser in NW OK, but this could be beneficial in lowering the LCL heights. Otherwise, the environment should be relatively homogeneous down the dryline.
Furthermore, tornado outbreaks in Oklahoma during the month of February are not unprecedented. On February 17, 1961, 9 significant tornadoes (8 F3 s, 1 F2) impacted C/E Oklahoma including a large tornado in Oklahoma County. See the following 500 mb plot: http://bangladeshtornadoes.org/UScas...2186100zh5.gif
Finally, CAPE is forecast to increase through the overnight hours as the 500 mb low approaches and cools temperatures aloft. Friday night could be very long for Oklahoma forecasters.
Gabe
A few thoughts about this potential event:
First, I think the timing of the wave is particularly good, according to the latest model runs. Most significant tornado outbreaks occur when increasing flow (at all levels) is coincident with peak heating/thunderstorm initiation. This will likely be the case Friday as mid and upper level flow increases dramatically during the afternoon and evening hours.
Also, the 12Z NAM shows a narrow instability axis in place by 00z Sat (6 p.m. Fri). The maximum in CAPE is progged to be in NW OK (~1500 j/kg). On the other hand, the NAM forecasts the greatest low-level shear (0-1 km) south of I-40. Thus, the best juxtaposition of favorable parameters appears to be close to I-40. This far out, it's pointless to banter about model output on such a small scale, but it is interesting to discuss possible scenarios (based upon experience and climatology).
I think the most likely scenario (see 3/27/04) is that several storms will form along the dryline (all potentially tornadic), but the greatest threat of tornadoes will exist on the northern end of the line. Temperatures will be slightly lesser in NW OK, but this could be beneficial in lowering the LCL heights. Otherwise, the environment should be relatively homogeneous down the dryline.
Furthermore, tornado outbreaks in Oklahoma during the month of February are not unprecedented. On February 17, 1961, 9 significant tornadoes (8 F3 s, 1 F2) impacted C/E Oklahoma including a large tornado in Oklahoma County. See the following 500 mb plot: http://bangladeshtornadoes.org/UScas...2186100zh5.gif
Finally, CAPE is forecast to increase through the overnight hours as the 500 mb low approaches and cools temperatures aloft. Friday night could be very long for Oklahoma forecasters.
Gabe
# posted by Gabe Garfield @ 12:30 PM 
