1st big storm went up by DDC in advance of the dryline along a cloud street. ci took 20-25 minutes. appears to have a second storm on its flank over the same initiation area. This area is where the winds have stayed from the southeast with dew points near 61 in DDC.
Storms that were ongoing associated with the low actually became tor warned first. DDC storms and initiation zippered along the dryline south still not doing much.
Cumulus cloud field sprang up in OK in apparent advance of the dryline where temperatures have gotten to 90 F with dew points into 20's. The structure of the cloud fields kind of resembles the model bulges in dryline position especially the NCAR ARW run from 00 UTC last night valid at 18 UTC. Indeed the OKMESONET says the dryline is in OK...what a surge that was...but probably not given the station spacing down there.
Northeast storm motion on these initial cells especially down into the woodward region. I am starting to think that a round 2 may be likely as the drying evident in water vapor imagery over the western TX panhandle increases and indicates that is the base of the shortwave trough. in advance of this feature is a secondary line of moisture evident on vis imagery which I believed to be part of the main dryline, but it may behind the surface dryline and may overtake the dryline in a few hours. This paradigm indicates a 2nd bout of CI as the forcing coincides with the dryline boundary...I am out on a limb here.
Monday, May 10, 2010
afternoon update
Indeed the severe weather risk areas migrate towards SW KS in advance of the surface low. Per my thinking in the previous post, storm initiation is indeed being forecast earlier. The dryline is really beefing up with dew points dropping down to near 10 F and surface winds sustained to nearly 35-40 mph with gusts to 50-60.
Current sat trends indicate multiple "cloud streets" though not of the fine scale variety behind the dry line. This indicates to me that low precip supercells may be the initial mode, however the speed at which the shortwave is progressing suggests that by the time CI does occur, they may be right in the moisture plume which argues against the low precip mode.
However, the linear banding of the cloud features at this point points to a more linear development mode. One wonders if this early convection, if it gets going, will be round 1 followed by round 2 of supercells later in the afternoon. Still more cloud lines popping up now near rthe dryline at 1715 UTC.
Waiting for 18 UTC sounding for DDC...maybe another hour or so before it appears on line if they launched at 1710 UTC like I hope they did. I also expect one from AMA at 18 or 21 UTC and one at OUN at 20 or 21 UTC. Hopefully the ARM site at LMN will also launch a few.
Dryline just went by Liberal KS, 82 over 45 this hour, was 75 over 59. Interesting that the dryline appears to be making north easterly gains into KS but not strong easterly surges in the panhandle ... recent trends indicate it is moving but not as fast further to the south. Will have to watch the progression.
Max dewpoints in OK up to 68 in the south, still holding strong at 65 in the plume to the north.
CI iminent along a line from the TX-OK border North to DDC in the next hour and a half over the OK panhandle.
Current sat trends indicate multiple "cloud streets" though not of the fine scale variety behind the dry line. This indicates to me that low precip supercells may be the initial mode, however the speed at which the shortwave is progressing suggests that by the time CI does occur, they may be right in the moisture plume which argues against the low precip mode.
However, the linear banding of the cloud features at this point points to a more linear development mode. One wonders if this early convection, if it gets going, will be round 1 followed by round 2 of supercells later in the afternoon. Still more cloud lines popping up now near rthe dryline at 1715 UTC.
Waiting for 18 UTC sounding for DDC...maybe another hour or so before it appears on line if they launched at 1710 UTC like I hope they did. I also expect one from AMA at 18 or 21 UTC and one at OUN at 20 or 21 UTC. Hopefully the ARM site at LMN will also launch a few.
Dryline just went by Liberal KS, 82 over 45 this hour, was 75 over 59. Interesting that the dryline appears to be making north easterly gains into KS but not strong easterly surges in the panhandle ... recent trends indicate it is moving but not as fast further to the south. Will have to watch the progression.
Max dewpoints in OK up to 68 in the south, still holding strong at 65 in the plume to the north.
CI iminent along a line from the TX-OK border North to DDC in the next hour and a half over the OK panhandle.
The morning update
Much to my surprise, the moisture is returning with dew points up to 60 in OKC at 15 UTC with a 65 just south into TX in the narrow plume of moisture to the west of FWD. It looks like the moisture is deep at FWD on the sounding from this morning. The shear is already large and there is no reason to suspect it will diminish. The hodographs are large and semi-circular from 0-3km.
Currently though there is a deep low cloud deck with indications of wave clouds. This corresponds nicely with OUN's sounding and low level stable layer. The water vapor imagery continues to indicate a dry intrusion aloft is setting up from MAF to OUN to Tulsa. The dryline itself is already in place at AMA, and should be moving rather quickly with the arrival of the shortwave in the next few hours. Convective initiation should occur according to the data prior to 21 UTC and possibly as early as 19 UTC if I have done my wave phase speed analysis correctly.
Presumed 700 hPa cold advection is already occurring into the TX panhandle. BIG question is when will the cloud cover break up over Oklahoma, and where it will recede long enough for temperatures to climb. If the clouds hold strong, which is in doubt, then where they do break up will determine the locations, at least partly, for CI. Sounds like May 3rd all over again.
East moving storms with right movers to the south-southeast. Gonna be a long day for some folks in Oklahoma. And SPC and I are of the same opinion ... maximum threat over a limited window of time. As per my discussion last night, the rightfully acknowledge the limited span of the best thermodynamics and rightfully acknowledge that the shear may be too strong such that storms may need time to fully organize. Thus the CI forecast location is somewhat removed from the maximum tornado risk area. I still wonder though if the environment is really conducive to long track tornados.
I think the answer is yes, but I wouldnt be surprised if a few storms go up, put down a tornado, then proceed to do nothing more that put down very large hail.
Also the nature of the straightline hodograph over the CI area might be conducive to splitting supercells initially. At least a portion of the northern end of the CI area may rapidly transition to an MCS.
ARW run from NCAR indicates that CI will occur by 20 UTC, and I would guess is probably an hour or two late given the use of the MYJ PBL scheme. But it does indicate that the threat area for more isolated storms along the dryline will be further south into Oklahoma. But once storms like these get going in the model there is no telling how correct it is given the bad mass fluxes at this scale (3 km). Suffice it to say the model is trending towards my line of thinking.
Clouds starting to thin over SW OK ... game on. First batch of CI I forecast for east of Liberal KS. If I were chaing today I would be in Oklahoma City east side waiting for data until 1pm.
Potentially dangerous situation tornado watchboxes should be the norm today.
Currently though there is a deep low cloud deck with indications of wave clouds. This corresponds nicely with OUN's sounding and low level stable layer. The water vapor imagery continues to indicate a dry intrusion aloft is setting up from MAF to OUN to Tulsa. The dryline itself is already in place at AMA, and should be moving rather quickly with the arrival of the shortwave in the next few hours. Convective initiation should occur according to the data prior to 21 UTC and possibly as early as 19 UTC if I have done my wave phase speed analysis correctly.
Presumed 700 hPa cold advection is already occurring into the TX panhandle. BIG question is when will the cloud cover break up over Oklahoma, and where it will recede long enough for temperatures to climb. If the clouds hold strong, which is in doubt, then where they do break up will determine the locations, at least partly, for CI. Sounds like May 3rd all over again.
East moving storms with right movers to the south-southeast. Gonna be a long day for some folks in Oklahoma. And SPC and I are of the same opinion ... maximum threat over a limited window of time. As per my discussion last night, the rightfully acknowledge the limited span of the best thermodynamics and rightfully acknowledge that the shear may be too strong such that storms may need time to fully organize. Thus the CI forecast location is somewhat removed from the maximum tornado risk area. I still wonder though if the environment is really conducive to long track tornados.
I think the answer is yes, but I wouldnt be surprised if a few storms go up, put down a tornado, then proceed to do nothing more that put down very large hail.
Also the nature of the straightline hodograph over the CI area might be conducive to splitting supercells initially. At least a portion of the northern end of the CI area may rapidly transition to an MCS.
ARW run from NCAR indicates that CI will occur by 20 UTC, and I would guess is probably an hour or two late given the use of the MYJ PBL scheme. But it does indicate that the threat area for more isolated storms along the dryline will be further south into Oklahoma. But once storms like these get going in the model there is no telling how correct it is given the bad mass fluxes at this scale (3 km). Suffice it to say the model is trending towards my line of thinking.
Clouds starting to thin over SW OK ... game on. First batch of CI I forecast for east of Liberal KS. If I were chaing today I would be in Oklahoma City east side waiting for data until 1pm.
Potentially dangerous situation tornado watchboxes should be the norm today.
May 10 the forecast for tornadoes?
It isn't rare to have a day 2 moderate risk for the central plains including OK and KS. It is rare to see a moderate risk during VORTEX2 operations ;) . The prevailing wisdom is that if you put 100 vehicles and 400 scientists and 8 radar trucks in the Plains ...ain't nuthin' going to happen.
So I thought I would get in on the forecast action.
Broad scale specifics from the NAM model: a sfc low races out of CO tonight across southern KS and moves into northeast KS by tomorrow night. This feature is due to a pretty sharp shortwave trough at 500 hPa (about half way up in the atmosphere in terms of mass) which gives the appearance of a negative tilt into tomorrow. Note that the flow around this trough (the jet streak too) is cyclonically curved. The jet streak itself is actually located across OK and TX panhandle. The jet streak at 300 hPa is located further north and there is a hint that the flow aloft will be anticyclonic in nature across southern Oklahoma.
Players in Convective initiation: The warm from will be a breeding ground for all kinds of convection tonight into tomorrow evening. The dryline will be a major player as it punches into Oklahoma City. BUT the shear appears to be oriented perpendicular to the boundaries ... a sign that storms should start and possibly remain discreet.
The odd things I see:
The motion is fast for the shortwave aloft, and thus the moisture return may be in question ... moisture takes time to be transported in great quantities. 0500 UTC data in Texas show 60's creeping into the TX panhandle but dew points only 50 at OKC and DFW. Hi-res NSSL model is consistent through 6 hours with observed data. Models are indicating this to be the case ... that only low to mid 60's with high temperatures near 83 will be possible, though behind the dryline it may hit 90.
NSSL model also indicating the low may stall. Operational models may be aggressive in bringing this system out. Complicating factor is the system to the NW that drops in behind, and system to the east which seems to not move too much. Hard to know since the jet aloft to the rear of the shortwave is not fully ashore.
Day 1 outlook updated to reflect a high risk. Can't argue against that. Models are all producing favorable parameters for Oklahoma tornados. This is easy to forecast maximum risk where all parameters come together nicely. However, as a chaser, where would you want to be knowing:
1. fast storm motions
2. seemingly moisture limited to the east (from the limited model runs I have seen)
3. complicated cloud forecast
4. complicated surface low and dryline evolution and thus placement.
It appears SPC is playing up the moisture (to 70 F) with temps in the mid 80's, and heavily favoring the track of the midlevel jet (rightfully so).
The BIG question is what kind of supercells will be the norm? low precip, high precip, or classic? If low precip come off the dryline how will they evolve in the face of ridiculous shear (40 meters per second) and a somewhat strong cap which is sure to come out given the steady fetch from ABQ?
I have to wonder if there will be early storms in KS that get into OK and further complicate this situation with outflow boundaries. There doesn't appear to be a whole lot of limiting factors the models are picking up on, so the devil is in the details ... morning models will be key as well as the radar and moisture progress on the soundings.
High risk is warranted but there is more going on here. May 3rd 1999 comes to mind in terms of an OKC to Tulsa outbreak. Needless to say I will have the radar looping tomorrow.
So I thought I would get in on the forecast action.
Broad scale specifics from the NAM model: a sfc low races out of CO tonight across southern KS and moves into northeast KS by tomorrow night. This feature is due to a pretty sharp shortwave trough at 500 hPa (about half way up in the atmosphere in terms of mass) which gives the appearance of a negative tilt into tomorrow. Note that the flow around this trough (the jet streak too) is cyclonically curved. The jet streak itself is actually located across OK and TX panhandle. The jet streak at 300 hPa is located further north and there is a hint that the flow aloft will be anticyclonic in nature across southern Oklahoma.
Players in Convective initiation: The warm from will be a breeding ground for all kinds of convection tonight into tomorrow evening. The dryline will be a major player as it punches into Oklahoma City. BUT the shear appears to be oriented perpendicular to the boundaries ... a sign that storms should start and possibly remain discreet.
The odd things I see:
The motion is fast for the shortwave aloft, and thus the moisture return may be in question ... moisture takes time to be transported in great quantities. 0500 UTC data in Texas show 60's creeping into the TX panhandle but dew points only 50 at OKC and DFW. Hi-res NSSL model is consistent through 6 hours with observed data. Models are indicating this to be the case ... that only low to mid 60's with high temperatures near 83 will be possible, though behind the dryline it may hit 90.
NSSL model also indicating the low may stall. Operational models may be aggressive in bringing this system out. Complicating factor is the system to the NW that drops in behind, and system to the east which seems to not move too much. Hard to know since the jet aloft to the rear of the shortwave is not fully ashore.
Day 1 outlook updated to reflect a high risk. Can't argue against that. Models are all producing favorable parameters for Oklahoma tornados. This is easy to forecast maximum risk where all parameters come together nicely. However, as a chaser, where would you want to be knowing:
1. fast storm motions
2. seemingly moisture limited to the east (from the limited model runs I have seen)
3. complicated cloud forecast
4. complicated surface low and dryline evolution and thus placement.
It appears SPC is playing up the moisture (to 70 F) with temps in the mid 80's, and heavily favoring the track of the midlevel jet (rightfully so).
The BIG question is what kind of supercells will be the norm? low precip, high precip, or classic? If low precip come off the dryline how will they evolve in the face of ridiculous shear (40 meters per second) and a somewhat strong cap which is sure to come out given the steady fetch from ABQ?
I have to wonder if there will be early storms in KS that get into OK and further complicate this situation with outflow boundaries. There doesn't appear to be a whole lot of limiting factors the models are picking up on, so the devil is in the details ... morning models will be key as well as the radar and moisture progress on the soundings.
High risk is warranted but there is more going on here. May 3rd 1999 comes to mind in terms of an OKC to Tulsa outbreak. Needless to say I will have the radar looping tomorrow.
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