Wednesday, February 28, 2007
FCST: 2/23/07
Today, supercells and tornadoes will be possible across eastern Oklahoma, southwest Missouri and eastern Arkansas. Concerns for today include: WSW 850 mb winds, a strong cap, moisture depth, and timing of the vorticity maximum. Conversely, favorable factors are: reasonably high magnitude of moisture return (Tds ~60 F), powerful upper-system (wind max of 150 kts), strong shear at all levels and low LCL heights.
The RUC now is very bullish in developing storms down the length of the dryline by 00z with initial development occurring by 21Z (3 pm CST). Hopefully, this indicates that the capping inversion will not be as significant as previously advertised. Even so, I plan on taking this a bit more cautiously since 1.) Cap busts are not fun, and 2.) The target area is reasonably close to my starting location.
My initial thought is to go northeast on I-44 and target the corridor between Tulsa and Bartlesville. Perhaps, it will be best to hedge southward initially since moisture return has already occurred in SE Oklahoma and will have undoubtedly reached EC Oklahoma by 00Z. I'm slightly concerned that moisture return further north will not happen, owing to the strongly veered winds that exist at 850 mb now.
TARGET: Bristow, OK
Gabe
The RUC now is very bullish in developing storms down the length of the dryline by 00z with initial development occurring by 21Z (3 pm CST). Hopefully, this indicates that the capping inversion will not be as significant as previously advertised. Even so, I plan on taking this a bit more cautiously since 1.) Cap busts are not fun, and 2.) The target area is reasonably close to my starting location.
My initial thought is to go northeast on I-44 and target the corridor between Tulsa and Bartlesville. Perhaps, it will be best to hedge southward initially since moisture return has already occurred in SE Oklahoma and will have undoubtedly reached EC Oklahoma by 00Z. I'm slightly concerned that moisture return further north will not happen, owing to the strongly veered winds that exist at 850 mb now.
TARGET: Bristow, OK
Gabe
CHASE: 2/23/07
On Friday, February 23rd, the SPC issued a moderate risk for severe thunderstorms and tornadoes (15% hatched tor). Moisture depth and quality remained an issue, which precluded the issuance of a high risk. This turned out to be a good decision since the verification of the event was in the slight risk regime (only a few tornadoes and hail reports). Nevertheless, Friday was a fun chase day.
Started out the chase in Norman, and we departed around 3 p.m. for the Childress area. This was a late departure time, but due to outstanding driving (;-)), we made it to the targete area by about 5:40 p.m. By this time, a full-fledged supercell had developed west of Memphis, TX, so we decided to target this storm. We saw this storm, and a very well-developed supercell to its north. The convection on the northern cell was particularly impressive, given the time of the year. Our storm had a flat base, but it was obviously rotating with an *extensive* beaver tail feeding the storm from the east. This might have been the most notable part of the storm, since I've never seen a bigger inflow band. At any rate, the storm began to produce lowerings around 6 p.m. We saw one RFD occlusion of a low-level mesocyclone, and it made a legitimate attempt at producing a tornado (two brief funnels were observed). After this, the storm became an HP supercell, which lowered our hopes of seeing tornadoes. Officially, this storm did produce a tornado around 6:15 p.m., but we were in the wrong position (apparently) to observe it. The northern cell also produced a tornado, but this tornado was far more visible as the northern storm was distinctly low precipitation in nature.
Overall, this was a very fun chase with good friends. :-)
Started out the chase in Norman, and we departed around 3 p.m. for the Childress area. This was a late departure time, but due to outstanding driving (;-)), we made it to the targete area by about 5:40 p.m. By this time, a full-fledged supercell had developed west of Memphis, TX, so we decided to target this storm. We saw this storm, and a very well-developed supercell to its north. The convection on the northern cell was particularly impressive, given the time of the year. Our storm had a flat base, but it was obviously rotating with an *extensive* beaver tail feeding the storm from the east. This might have been the most notable part of the storm, since I've never seen a bigger inflow band. At any rate, the storm began to produce lowerings around 6 p.m. We saw one RFD occlusion of a low-level mesocyclone, and it made a legitimate attempt at producing a tornado (two brief funnels were observed). After this, the storm became an HP supercell, which lowered our hopes of seeing tornadoes. Officially, this storm did produce a tornado around 6:15 p.m., but we were in the wrong position (apparently) to observe it. The northern cell also produced a tornado, but this tornado was far more visible as the northern storm was distinctly low precipitation in nature.
Overall, this was a very fun chase with good friends. :-)
FCST: 2/28/07
Today, supercells and tornadoes will be possible across eastern Oklahoma, southwest Missouri and eastern Arkansas. Concerns for today include: WSW 850 mb winds, a strong cap, moisture depth, and timing of the vorticity maximum. Conversely, favorable factors are: reasonably high magnitude of moisture return (Tds ~60 F), powerful upper-system (wind max of 150 kts), strong shear at all levels and low LCL heights.
The RUC now is very bullish in developing storms down the length of the dryline by 00z with initial development occurring by 21Z (3 pm CST). Hopefully, this indicates that the capping inversion will not be as significant as previously advertised. Even so, I plan on taking this a bit more cautiously since 1.) Cap busts are not fun, and 2.) The target area is reasonably close to my starting location.
My initial thought is to go northeast on I-44 and target the corridor between Tulsa and Bartlesville. Perhaps, it will be best to hedge southward initially since moisture return has already occurred in SE Oklahoma and will have undoubtedly reached EC Oklahoma by 00Z. I'm slightly concerned that moisture return further north will not happen, owing to the strongly veered winds that exist at 850 mb now.
TARGET: Bristow, OK
Gabe
The RUC now is very bullish in developing storms down the length of the dryline by 00z with initial development occurring by 21Z (3 pm CST). Hopefully, this indicates that the capping inversion will not be as significant as previously advertised. Even so, I plan on taking this a bit more cautiously since 1.) Cap busts are not fun, and 2.) The target area is reasonably close to my starting location.
My initial thought is to go northeast on I-44 and target the corridor between Tulsa and Bartlesville. Perhaps, it will be best to hedge southward initially since moisture return has already occurred in SE Oklahoma and will have undoubtedly reached EC Oklahoma by 00Z. I'm slightly concerned that moisture return further north will not happen, owing to the strongly veered winds that exist at 850 mb now.
TARGET: Bristow, OK
Gabe
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
