Wills' Geek Weather

Tornado Watch

1 P.M. Friday, April 10, 2009
Tornado Watch has been extended northward to cover just about all the WAVE 3 viewing area.  Not to worry.  Little has changed.  Primary upper system will move over KY this afternoon keeping primary threat from winds/tornadoes from the southern third of KY down into TN.  After our hailers around the area this morning, the rest of the afternoon should be quieter here - some showers/t-storms, but severe storm chances look very slim.

deja vu?

Midday Thursday, April 9, 2009

We've had a long series of upper troughs digging into the western U.S. and then curving around toward the eastern U.S.  Most recent one should be here tomorrow with a rainy day.  Earlier, it looked like we'd see a lot of rain (1-2") in Louisville and higher totals over southern Indiana.  Plus, the models were taking the weakening surface low north of the Ohio River.  That would open the door to severe weather.

The 12Z runs this morning have made a big shift in keeping the upper low and the surface low south of (or right over) the Louisville area.  If that verifies, it really changes things for us:  1). rain starts later (midnight or after) and ends up being about an inch less than previous expectations (good news for flood-prone southern Indiana), and 2). severe thunderstorm threat drops south (out of the Louisville area) although southern KY and TN could see strong to severe storms late tonight and/or late tomorrow.

Severe storm threat diminishing.

5 P.M. Sunday April 5, 2009

Low pressure cutting across southern Indiana and a very strong upper level wind field, seemingly ideal conditions for severe storms, so far have combined for a lot of rain, but not the outbreak of severe storms expected earlier.  Moisture has been the problem as the instability of the atmosphere has remained very weak.  So far, the upper air dynamics have been unable to overcome the lack of strong instability.  And, at least as far as our area is concerned, it looks like the system is running out of time.  Numerous showers and thunderstorms cover southern Indiana and western KY.  As of 5 P.M., the strongest thunderstorm nearby was over southern Breckenridge County and moving eastnortheast about 40 mph.  Up until 7 P.M., the initial line of thunderstorms will move through the Louisville area and most of KY west of I-65.  If anything strong or severe is going to develop, it'll be with this line.  But, that remains doubtful as instability remains very low and will be dropping.

So, in a nutshell, the threat for severe thunderstorms is very small and diminishing quickly.

Tornado Watch

2 P.M. Sunday, April 5, 2009

Tornado Watch until 7 P.M. for western half of KY and SW quarter of IN. 

Certainly looks like the moisture is going to get here and the classic severe pattern remains in place.  So far, nothing is going on, but look for that to change soon.  We'll probably start getting severe reports by 3 P.M. out of western KY and southern IL.

Severe storms possible by late afternoon.

11 A.M. Sunday, April 5, 2009

Conditions continue to look more and more like we'll be under the gun for severe storms later today (probably in Louisville area between 5 and 8 P.M.).  Strong surface low will cross southern IL/IN this afternoon and evening.  That puts all the "dynamics" in place for severe storms over southern IN and KY.  Only missing ingredient currently is moisture and that seems to be racing northward along the Mississippi Valley and spreading eastward.  In fact, thunderstorm initiation has occurred earlier than anticipated, so it looks as though enough moisture will arrive in time to be in play as the cold front moves across southern IN and KY late this afternoon and evening. 
   Assuming moisture does arrive, the scenario should play out about like this - several supercells should pop up over western KY and southwest IN early this afternoon.  Would not be surprised if they produced some tornadoes.  With time (and before it approaches the I-65 corridor), the system should evolve into more of a linear thunderstorm complex.  Primary threat would then shift to hail and (especially) high winds. 
   However, there is a chance that some additional discrete supercells could still form out ahead of the primary thunderstorm line.  If so, watch out! They could spin up some tornadoes.
     Trying to read the Storm Prediction Center's mind...I'd imagine we'll go under a Tornado Watch this afternoon.  However, for most of us the primary threat will not be from tornadoes.  Rather, straight line wind gusts of 50-70 mph could be fairly common.

Rainy night

7 P.M. Thursday, April 2, 2009

SPC hates to give up, but it looks like any threat for severe weather is fading fast.  So, we'll probably be needlessly under a Tornado Watch for several more hours.  But, a large area of moderate to heavy rain/thunderstorms will move over the area for the next few hours.
Shakespeare got this one right centuries ago - "Much Ado About Nothing."

Plenty of rain...

Midday Thursday, April 2, 2009

GFS and WRF/NAM have strongly gone back to their "southern solution" I talked about yesterday (see Blog).  Major outbreak of severe stroms looks likely over the deep south today/tonight.  That will prevent a lot of moisture from getting into our area.  However, this is a very strong system and should generate plenty of rain and thunderstorms over KY and southern IN.  Primary surface low expected to go from Memphis this evening to east of Cincinnati by tomorrow morning.  That track keeps the low south of the Louisville area.  It also keeps our threat for severe storms very low.  South and east of the low's track, however, should be on the watch for powerful, damaging storms, especially from TN southward.

Beautiful day!

Midday Wednesday, April 1, 2009

What a beautiful day!  Think I'll get out and enjoy nature this afternoon (I have to cut the grass!).

Meanwhile, tomorrow is taking on a different look.  Yet another in the seemingly never ending upper level disturbances to come off the Rockies will do so tomorrow.  Recently, most of these have headed northeast.  This one, however, looks like it'll dig farther southeast before making the curve northward.  Earlier it looked like the upper trough and surface low would move over KY and thus keep any serious threat for severe storms far to our south.  But, with the 12Z runs this morning, the often see model "correction" has set in with the WRF/NAM (especially) and GFS starting to predict a more northerly storm track.  That could open the door for at least the possibility for severe storms in the area late tomorrow/tomorrow night.  At this point, it looks almost like a repeat of last Saturday's system - primary area/threat for severe storms stays to our south but an isolated storm or two could get up to the Ohio River.

Hope to have a clearer picture on this tomorrow.