4/18/06 FCST: IA/MO/IL/AR/TX

[Bill Schintler]

Chase target:
7 miles S of Marshall, MO (I-70, mile marker 78).

Timing:
Storm initiation at 4:30 though 5 PM CDT, storms will become severe by 6 PM.

Comments:
A significant although limited in aerial coverage severe event is expected today. Supercells and tornadoes will be likely near the target area, while a large area of mostly non-severe storms will break out in the northeast third of MO.

Discussion:
Developing SFC WF will be the focus for severe WX today as a low approaches the area under the exit region of a 70kt H3 max. Along and S of this SFC boundary, ample instability (SBCAPEs to 2000 J/kg and MLCAPEs (100mb) of 1500 J/kg) will be in place. Despite a concern with the relatively weak mid-level winds today, decent deep-layer shear (0-6km) of 35-40kts will exist at the nose of the stronger H5 streak. Additionally, expect locally nice hodograph curves in the lowest 1 km, with ERLY to SERLY SFC winds of 20-25kts under weak H8 flow of under 10kts, immediately NE of the aforementioned boundary. Cloud bases will be 800m to 1000m in this area. Although capping will remain significant for much of today, a band of enhanced mid-level assent heading E at 30kts, event on WV loop along an ICT/MHK/JYR line at 16Z, will provide the necessary lift to initiate convection as it arrives in WRN MO later this afternoon.

- bill

 

[Paul Knightley]

Hi,

Another virtual chase from England is setting up! Having looked at the data, I've picked the area close to Columbia, MO, for this set-up - as I see several others have too!

I like the strongly backed surface flow here, and the progged depression should give some extra surface convergence/uplift. That backed flow should be enough to get some supercells going, although my personal feeling is they'll be quite HP/outflow dominant, given the weakness in the mid-level flow. However, the high moisture loading of the lowest 1km *could (IMO) limit the cold-pool generation potential, so despite some HP cells, the RFDs may have enough downdraught CAPE to allow tornadoes to form, in which case, some nasty rain-wrapped ones could form. I notice that the latest profiler obs from Conway, MO, have 40 knots from the SW @ 500 hPa, so there could be just a little more mid-level flow than progged by the models.

Paul.

editing for spelling.

 

[Tim Vasquez]

Does anyone have a source of satellite data newer than the 1915Z shot I'm seeing everywhere (currently 2010Z)?

Tim

 

[Kevin Askew]

Does anyone have a source of satellite data newer than the 1915Z shot I'm seeing everywhere (currently 2010Z)?

Tim
[/quote

Nope all mine 1915 as well

 

[Adam Holle]

Does anyone have a source of satellite data newer than the 1915Z shot I'm seeing everywhere (currently 2010Z)?

Tim
[/b]

Did you try Colorado State University CIRA? I updates every 5min

 

[Kevin Askew]

Does anyone have a source of satellite data newer than the 1915Z shot I'm seeing everywhere (currently 2010Z)?

Tim
[/b]

Nope all mine 1915 as well :unsure:

 

[Jayson Prentice]

The CIRA site has the 2130z satellite image, they update often and usually are very good.

http://www.cira.colostate.edu/Special/CurrWx/G10arm10.asp

 

[Bob Schafer]

Is that working because it's GOES West? (right?), or is it a problem with all satellites?

I'm on US50 between Lone Jack and Pittsville, and.....gotta go. Towers going up as I write.

 

[Tim Vasquez]

Good catch. That CIRA GOES-WEST sector is the absolute only image I've been able to find anywhere that's current. I actually went to Google news to see if there was some sort of emergency somewhere that might have taken down Wallops Island or Washington, but couldn't find anything.

Here's a version of their latest 2030Z GOES-WEST image without the severe distortion.

Tim[attachmentid=163]

 

[Paul Knightley]

Good catch. That CIRA GOES-WEST sector is the absolute only image I've been able to find anywhere that's current. I actually went to Google news to see if there was some sort of emergency somewhere that might have taken down Wallops Island or Washington, but couldn't find anything.

Here's a version of their latest 2030Z GOES-WEST image without the severe distortion.

Tim[attachmentid=163]
[/b]

Without knowing the full details of your US satellite set-up, I'm not sure whether this link http://www.ssd.noaa.gov/PS/SATS/SPBULL/MSG1081454.01.txt is of any use, w.r.t this problem.

 

[Tim Vasquez]

Updated 2100Z image rectified for severe distortion from GOES-WEST.

Tim

 

[rdale]

GOES-East was down for a scheduled / announced manuever.

 

[Jeff Snyder]

It's nice to see a 21z sounding from KSGF --> http://www.spc.noaa.gov/exper/soundings/06041821_OBS/SGF.gif , which shows an essentially-uncapped environment (CINH negligible for surface-based parcel, weak for a mixed-layer parcel) with strong to extreme instability (observed CAPE >4500 j/kg is respectable any time of the year). I would a bit surpised to see how quickly the cap eroded between the 18z and 21z soundings. Initiation is occurring in northwestern MO right now, near the intersection of two boundaries / fronts seen on the EAX radar (cold front and dryline most probably, though the lack of surface obs between the boundaries makes that identification a little difficult). 40kt 0-6km shear observed at SGF would support supercells given the strong instability, though the weakness in the midlevel flow (25kts at 500mb) makes me think HP. At least the anvil-level flow (~200mb) is decent (60-70kts). Current visible sat imagery indicates Cu developing along the dryline, from east of Kansas City to near Springfield. The most favorable area for tornadoes, IMO, appears to be setting up near I70, with Jefferson City (south of Columbia) sitting at 90/64. LCLs are quite high, but the backed flow near I70 may enhance low-level shear to compensate a bit. Lathrop profiler showing that the vertical shear is favorable for a decent supercell and tornado threat.

Edit: CoD is showing that the 21z SGF sounding has 3100j/kg CAPE vs. the 4600 j/kg CAPE per the SPC page...
Edit2: Looking at the CoD sounding, it looks like they take some sort of mixed-layer / mean-layer parcel when computing CAPE, which makes sense since the CoD-derived CAPE compares pretty well with the SPC MLCAPE.