Joshua T. Clark
EF2
I am surprised that no one has started a thread for the day. Looking like another dangerous day for Dixie Alley.
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2014-04-29 FCST: LA MS AL
- Thread starter Joshua T. Clark
- Start date
Jeremy Perez
Supporter
I have low confidence in my abilities on setups like this, but I'm running a virtual chase on it and this is what I posted to my site last night—
Upper level low over eastern Iowa with 70-80 kts of flow over Louisiana/Mississippi/Alabama. Surface low is stacked right under its upper level partner. A cold front wraps through western Kentucky/Tennessee, northwest Mississippi and northern Louisiana at 18Z and pushing slowly southeastward during the afternoon. Upper 60 to 70 degree dew points are in place early with surface winds veered more strongly the further north you go approaching the front. CAPE values over the southeastern two-thirds of Mississippi, boot of Louisiana, and west-central Alabama start off over 3000 j/kg at 18Z and get eaten away by convection as the day goes on. Bulk shear over this strong instability is over 60 knots early on but relinquishes its hold over most of southern Alabama by late afternoon. 0-1km SRH is in the 150 m^2/s^2 over the southern third and a central pocket of Mississippi and floats ahead of developing convection. EHI is pegged over 3 in those central and southern pockets of Mississippi at 18Z when convection is heating up. Convective models show an early start to storms with supercells forming by midday in Mississippi and moving into Alabama during the afternoon. This is still early, messy convection and difficult to untangle options. For virtual chasing, I'm targeting Paulding, Mississippi.
[Edit: this was based on quick analysis before 00Z model output and favored NAM. That 3000 j/kg has not materialized even remotely. But an outflow boundary in southeast Louisiana appears to be funneling 2000 j/kg northeastward and into Mississippi.]
Upper level low over eastern Iowa with 70-80 kts of flow over Louisiana/Mississippi/Alabama. Surface low is stacked right under its upper level partner. A cold front wraps through western Kentucky/Tennessee, northwest Mississippi and northern Louisiana at 18Z and pushing slowly southeastward during the afternoon. Upper 60 to 70 degree dew points are in place early with surface winds veered more strongly the further north you go approaching the front. CAPE values over the southeastern two-thirds of Mississippi, boot of Louisiana, and west-central Alabama start off over 3000 j/kg at 18Z and get eaten away by convection as the day goes on. Bulk shear over this strong instability is over 60 knots early on but relinquishes its hold over most of southern Alabama by late afternoon. 0-1km SRH is in the 150 m^2/s^2 over the southern third and a central pocket of Mississippi and floats ahead of developing convection. EHI is pegged over 3 in those central and southern pockets of Mississippi at 18Z when convection is heating up. Convective models show an early start to storms with supercells forming by midday in Mississippi and moving into Alabama during the afternoon. This is still early, messy convection and difficult to untangle options. For virtual chasing, I'm targeting Paulding, Mississippi.
[Edit: this was based on quick analysis before 00Z model output and favored NAM. That 3000 j/kg has not materialized even remotely. But an outflow boundary in southeast Louisiana appears to be funneling 2000 j/kg northeastward and into Mississippi.]
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Jeremy Perez
Supporter
Also, per MD0479, it's interesting to see how the MCS that evolved out of yesterday's storms has really punched a hole in CAPE potential in Alabama and parts of Mississippi throughout the day. Ongoing convection down along the gulf is also pumping ongoing anvil cirrus over the area and keeping temps down. Storms trying to fire ahead of the cold front in Mississippi appear to be struggling further south vs. that outflow & anvil cover.
Joshua T. Clark
EF2
I would definitely agree, convection seems to be having a hard time staying organized.
Jeff House
Supporter
Looks like the Gulf Coast MCS continues to disrupt recovery in the rest of the South. MD 479 is excellent from SPC discussing the BMX sounding. Now supercells are trying but appear low-top as of 4:00 Central; it's still early. It is possible subsidence behind the morning jet max now over TN/KY is still hampering things too. Back jet max coming out of Louisiana might enhance things toward dark. Today was supposed to go earlier than yesterday; but, now there is an outside chance it blooms later. LLJ currently going into NC might shift back into AL and East Tenn per the back jet max. 18Z NAM has some mean qpf/radar forecasts for the Tennessee Valley. It might be overdoing it if the sounding never recovers. On the other hand later means more time for it to recover.
