Wednesday, June 01, 2011

June 1: A good day to chase

Based on the model forecasts I left home for Culpeper early this afternoon and arrived there around 2:00 p.m. to await convection given the monster CAPE values (>6000!) in northern Virginia.  Turned out that I was a bit early as things didn't start bubbling until 4:00, when several updrafts formed and almost immediately were tagged with hail icons on radar.  Fortunately they were moving slowly at around 15 knots so I didn't have to make immediate decisions on where to go.  I wandered around the Culpeper vicinity for a while, stopping to watch a rain free base under the first cell to see if any lowerings would occur:
Nothing formed so I moved south along Route 522 to stay ahead of the developing line of storms as the cells coalesced until I realized that I could get far enough south on that highway to catch the "tail-end Charley" storm.  Stopping a few miles south of Unionville I watched that cell crawl in my direction as it exhibited another rain free base:
Nothing showed under this storm either as the rain shaft pounded down just a couple hundred yards to the north.  I had just about decided to pull back out onto Route 522 and head back north when this cell exploded with numerous CG's (cloud-to-ground lightning) and hail started to fall.  The storm intensified literally over my head as I watched - and listened to - a ten minute hailfall that started with half-inch stones and wound up pile-driving my car with stones up to 1.5 inches in diameter:
The quarter (1" diameter) is shown for comparison.
(Note:  my chasemobile actually has a few hail dents now...source of a chaser's pride!)

After the very noisy hailfall finished I did head north and then back home, not wanting to chase that storm through the wilds of Spotsylvania county and around Lake Anna.  At home all was dry and storm-less, but a magnificent mammatus display near sunset made it all worthwhile:

2 comments:

Mark said...

I too was surprised at how fast cells in the Fairfax area went from a green blip on radar to getting the "hail icon". I suppose there's more to that algorithm than just dBz of reflectivity, it may factor in storm height, temps, and mid-level lapse rates as well.

Chris White said...

Mark,
The overall factor in the quick hail ID was most likely the enormous CAPE available. The updrafts were very strong right from initiation.