Another curtain call for the "Toilet Bowl"

Today's total rainfall map via the Sterling NWS radar.  See the white circle within which there was no rain today?  Need I say more?

Nothing chaseable so far

Storms fired this afternoon along a lee trough east of the Blue Ridge, with the best action fading northeastward into the DC metro area where I refuse to chase.  There were several severe TS warnings there, but we missed all that action.  Nonetheless we were still under a severe TS watch so I had hopes of other storms to chase but none of the other updrafts really got juiced like the early ones.  Still, I was able to park at the local elementary school and watch as one updraft intensified just north of town, interacting with an outflow boundary coming south from the early storms. 

Pretty cool structure shot, but nothing severe to write home about.  I'm still watching radar in case the approaching cold front fires up more action.

Monday to the rescue

A rather vigorous cold front is forecast to wash through here Monday, bringing a small chance for severe storms and ushering in cooler more June-like weather for the latter half of the week.  The SPC Day 2 outlook only shows our area firmly under a 5% chance of severity, with the forecast text throwing out all sorts of caveats as to why we might not see much.

I haven't scrubbed through the model forecasts yet - altho' I will later today - so I don't have a feel for whether the true outlook for severe storms tomorrow is better or worse than the above graphic shows.  The NWS Sterling office has us down for a 40% overall chance of storms, so it seems our chances for some rain are decent.  At any rate my chasing radar is up and running.

UPDATE (1530):  Looks like the SPC thinks things will be a bit more unstable tomorrow.  After a quick look at one model I see speed shear and bit of directional shear coupled with decent - altho' not overly impressive CAPE - so it looks like tomorrow I'll be in chase mode if at all possible.  (Also watching a complex of storms pushing through Spotsylvania and Orange counties at the moment.  If they get close enough and look vigorous enough I may stray outside in today's heat to take a gander.)

Classic example of the Fredericksburg "Toilet Bowl" effect

Today's cold frontal passage provides more fodder for my pet hypothesis regarding the "Toilet Bowl" effect regarding the tendency of storms to divide around - and miss - Fredericksburg.  As the hypothesis goes, with a generally northwest-to-southeast track of storms (typical of cold frontal passages) across Northern VA something upstream of Fredericksburg creates a "roadblock" of sorts that kills convection before it gets here.  (This is not true of other storm directions.)  I'd bet that it's something in the topography northwest of here that helps suppress convection headed for Fredericksburg.   Maybe that's worthy of a research grant;  hmmmmm....

Catching up, getting ready

I need to write up Tuesday's (6/22) chase before I chase this afternoon, as a cold front is kicking off a line of storms that is approaching from the northwest.  Anyway Tuesday's setup looked good for mid-afternoon as two of the local models showed a few storms firing by 4 pm, with everything being east of I-95 by 6-7 pm.  Thus I made my way to the Culpeper vicinity by 3 pm to make ready, and within 30 minutes two updrafts fired in Greene county just north of Charlottesville.  Rollling south on U.S. 29 I stopped in Ruckersville to face westward and observe the approach of the western storm and noticed another cell going up on its northern flank.  This one showed indications of a wall cloud but little or no precipitation early in its cycle:

Twelve minutes later this feature showed up which I have since classified as a probable funnel vice just scud:

As this cell built and moved eastward it quickly became an HP (high precipitation) cell and I moved back northward on Rte 29 to stay with it.  Unfortunately after a brief intensification it decided to rain out and eventually disappeared within 45 minutes.  I motored back up to Culpeper and checked radar (no echoes within 100 miles) and conditions (surface trough was moving east of I-95), and decided to call it a day based on those checks and the model forecasts from earlier in the day.
UNFORTUNATELY,  my prognostication was flawed and a short line of intense storms formed 3 hours later - from Culpeper north toward Warrenton - via the lift provided by an approaching short wave.  Caught out of position I chased very locally, winding up on Brooke Road 3 miles NW of Fredericksburg and catching sight of a wall cloud (looking northward) on the southern edge of a nice-looking rotating updraft:

This feature was accompanied by frequent CGs and what appeared to be an inflow band streaming in from the southwest:

I called this in to the NWS Sterling office and then tried to give chase to this cell which was already approaching the Potomac River.  I ran out of visibility and real estate and didn't see anything else even tho' this storm crossed into southern Maryland and wreaked all sorts of wind damage. What was that again?  Oh yeah, never give up too early on a chase!

Very quick recap of today

(a) I did chase...twice.
(b) I saw a probable funnel on one storm and called in a rotating wall cloud report on another (the northern warned storm shown below with velocity data - yes it was rotating.)

(c) I blew one of my own chasing axioms:  never give up too early...but I'll get to that later.

SPC agrees with Tuesday

The Storm Prediction Center has extended their Slight Risk area further east and south to cover most - if not all - of my chase areas, so it would seem that they agree with me on the potential for severity tomorrow (that sounds a bit pompous written like that...).  At any rate I will be keeping an eye on the radar tomorrow and will head out at the first availability opportunity to spy on the sky.  Instability and a modicum of wind shear should couple with a frontal approach to provide some fireworks.

Tuesday's agenda: Chasing

This forecast graphic for 8 pm Tuesday shows a decent amount of CAPE (instability) for our region, and the SPC also has us in/near a Slight Risk region.  A survey of the models shows some directional wind shear (change in direction with height) but not a lot of speed shear, typical of summertime conditions here.  The models also indicate a lee trough east of the Blue Ridge which would provide the lift mechanism needed for storms to form.  Thus, we will likely have some scattered thunderstorms Tuesday afternoon and evening (20% chance according to NWS Sterling) and they will likely be slow movers of the west-to-east variety.  The interesting part about the latter factor is that I have witnessed very few - if any - southwest to northeast moving storms this spring, which is the typical storm motion direction for us.  The upper level weather pattern has been atypical this spring and there doesn't seem to be any indications of a change anytime soon.

Can't make 'em all!

I had every intention of chasing this afternoon, especially given the available instability and shear values.  However after a night of little sleep and after spending all day slouching around the house not feeling well I decided discretion was the better part of valor and stayed home today.  If I had chased I would have been on the above cell currently plowing through southern Spotsylvania county.  This cell had a severe warning on it when it punched through the town of Orange, and it has had radar-indicated rotation on it for quite a while.  My guess is that it has a substantial wall cloud on its southern edge and may have dropped a funnel or two by now.  Oh well, (refer to the blog post title)...

Chase today too!

Yep!  Storms and a chase of sorts happened. I noticed on radar a nice looking cell crossing northern Stafford county that appeared to be turning right - a good sign of severity - as it neared the Potomac River so I pointed the chasemobile to the nearest school parking lot and quickly found that I couldn't see well enough underneath what I knew to be a large rain free base.  With my chasing antenna prickling I maneuvered my way via back roads down to the edge of the Potomac where I caught this view at 5:58 pm of what appeared to be a wall cloud that I couldn't see clearly:

Turns out this likely was a wall cloud, since the radar view at 5:43 pm showed a tornado signature:

Frustrated at not being able to see this base clearly, and not wanting to head further east into the wilds of the Potomac River edges of King George county, I motored back toward home and noticed yet another complex moving into the area.  I parked at the school I had originally made for and watched the approach of a curious feature that appeared to be the beginnings of a forward flank mesocyclone as seen in the differences between the first (6:13 pm) and second (6:22 pm) photos below:

By the time of the second photo I was almost certain it was slowly rotating, but I wasn't sure for a few minutes more.  As the leading edge passed almost overhead the left-to-right circulation of this feature became evident.  (I took some video but will have to edit it before posting.)  Only saw one CG and heard only a bit of thunder to go along with the pounding rain, but it was a chase nonetheless!

Yesterday's "chase", watching radar today

A few showers rolled through the area early yesterday afternoon, preempting later convection that may otherwise have been more vigorous.  Tired from a very busy weekend, I first headed out with the intention of just stopping at a local school parking lot to watch the storm's approach:

As shown in this photo there was a distinct rain-free base to the south of the rain shaft, but it was definitely outflow-dominant so no hope of a wall cloud.  In fact, I never heard thunder or saw lightning from this complex but I did give in to my chaser's impulse to wearily trudge after it into King George county, where I watched as it merged with other growing cells to form a convective line that marched south and east.

This afternoon there is a relatively weak short wave that is pumping up convection near an also weak "cold" front that should slide south of here tonight.   I am watching a few showers on radar but nothing exciting is happening yet.

Another wall cloud report, another tornado warning

I positioned myself in Bealeton just off Rte 17 around 2:30 pm this afternoon, plotting my trajectory against the oncoming storm trajectories via radar.  Given that a nice-looking cell was moving east from the Culpeper vicinity I chose to move east and south along Fauquier county back roads, winding up in the southeastern corner of the county near the hamlet of Somerville.  This photo was taken looking almost due west, showing what I identified as a rotating wall cloud south of the main rain shaft.

 

  I called it in to the NWS Sterling forecast office at 3:21 pm, and at 3:30 pm they issued a tornado warning for Fauquier and Stafford counties for this cell (tornadic signature seen here):

As the rain shaft caught up with me I moved further south and east, winding up in northwestern Stafford county desperately trying to keep an eye on that part of the storm while avoiding the heavy rains.  I wound up unsuccessful at both attempts, winding up punching the core of a tornado-warned storm!  I didn't experience anything other than heavy rain and a few CGs, so I wasn't really worried with no wind or hail evident.
I followed the building line through Stafford county into western King George county, enjoying an extended vista of the entire line but not witnessing anything else severe.  All in all another good chase!

It's on!

The system that has dropped tornadoes and other severe weather across the northern Plains and Upper MidWest this week is finally here, and it looks like a chase day to me!  More later...

UPDATE 1:45 pm:  Tornado Watch!!!  I'm heading out shortly.

Good decision, but it meant a Caroline county chase

The title isn't meant to disparage the county or its residents, but it does refer to the undesirability of storm chasing there due to the lack of roads and the plethora of trees that prevent a good field of vision most places.  I waited to leave the house until radar verified a cell heading eastward across Spotsylvania county was actually holding together and even intensifying, since most of the updrafts I was eyeing had fallen apart prior to reaching I-95.  This methodology worked only because the cell I chose to chase was moving relatively slowly (18 knots), leaving me free to cruise down Route 2 before turning westward on Stonewall Jackson Road (Rte 606).  As I espied the southern edge I noticed a rain free base, which immediately sharpened my focus.  Searching for a path to the south I wound my way along until plunging southward on Rte 632 and found a spot to view the oncoming storm.  This photo - at 5:03 EDT - shows a lowering that I deemed a wall cloud as I detected a wee bit of low level rotation on the radar view:

Six minutes later I snapped this closeup of scud gathering at the southern edge of the rain shaft:

I never visually detected rotation, but speeding up the video 8x shows obvious rotation on a significant wall cloud (better view than any of my still shots).  Don't believe I witnessed a funnel tho', just leftover scud.
After the rain shaft got too close I motored further south into Caroline county, zooming through the countryside looking for viewing spots and not finding many.  I wound up going through the metropolis of Bowling Green and settling southwest of there off Route 207 as the storm passed overhead.  Good chase, and even more so after I reviewed the video!

The surge continues

The early June surge of storminess looks to continue both today and tomorrow, with most of the models for today calling for our area to be at the southern end of a "lee trough" which should fire off convection near I-95 between 3: 00 and 4:00 pm.  With a bit of speed shear evident in the models and some low-level boundaries we could see some storm rotation this afternoon.  We are also at the southern edge of the SPC's Day 1 Slight Risk for severe weather, so I'll be chasing locally today.
As for tomorrow afternoon a cold front is forecast to plow through here and provide us with a couple days relief from the heat and humidity.  That front will also trigger some storms - some severe - so I'll have my chase gear ready tomorrow as well.
Another note:  the second edition of this year's Hokie Stormchasers is off and running, placing themselves today in the middle of the SPC's Moderate Risk for the upper Midwest.  Go Hokies!

UPDATE 3:20 pm:

Cells firing over Culpeper county, heading generally in this direction.  I'm keeping an eye on them to see if / where I might intercept them.

Yet another Severe TS watch!

We're under another Severe Thunderstorm watch until 10:00 pm local time tonight.  Right now radar is showing a short line of cells just east of the Blue Ridge, lined up from Culpeper county down through Greene county.  Just got back home from moving my daughter from one apartment into another so I haven't had the chaser's hat on today.  Howsomever, if a nice-looking storm comes near here I'll be "forced" to check it out.

UPDATE 7:50 pm:  This line is dying with the lowering sun.  There's another line in the Shenandoah Valley north of Luray, but that's way too far off for me to think about chasing even if fading daylight wasn't a problem.   Maybe tomorrow...

Culpeper / Orange / Louisa county chase

Today was another early chase, evidenced by the fact that I was back home by 5:45 pm.  A complex of storms pushed across West Virginia and fired more storms over the Shenandoah Valley, so I decided to intercept these new storms as they crossed the Blue Ridge and - hopefully - before they coalesced into a line.  (Single cells are easier to chase.)  I made my way toward Culpeper, stopping to review the radar before heading southward down Rte 522 to sit and wait on things to percolate.  I noticed a nice-looking cell on radar just north of Charlottesville that was out ahead of the approaching line and heading my way, so I moved southward to avoid the oncoming rain and intercept this Severe TS warned storm.  During one stop to review the radar and watch the fast approaching line I snapped this photo of a shelf cloud segment to the west:

Continuing to escape the oncoming rain southward on 522 I stopped at a favored viewing spot and found via radar that the single cell had merged with the line, so I gave up trying to intercept it and moved to a spot in Louisa county just south of Ware's Crossroads to perform a "static core punch" of the now-solid convective line.  This was one of the photos I snapped there (greenage?) as a nice bow echo passed by just to my north:

After the heavy rain and CG's washed over my position I turned back north to verify hail in the bow echo but never found anything more than rain.  No hail, no rotation, no wall clouds...but a good chase nonetheless.

June 3rd Culpeper county initiation

Sitting here in Culpeper county awaiting a line of storms to cross the Blue Ridge and reform.  The SPC has placed our region under a Severe TS watch, so I'm keeping an eye on things here and points east...

UPDATE 3:25 pm:  Supercell composite up to 2 here.  Cells are crossing ridge line now; watching them visually and on radar.

UPDATE 4:35 pm:  One heckuva bow echo just to my north!!

Tuesday in Culpeper and Orange counties

The local forecast models called for two lines of storms to develop today:  one early in the afternoon (~2 pm) associated with a lee trough over the Piedmont and the other later (~ 5 pm) associated with an approaching weak cold front.  The former convective line occurred, while the latter didn't. Due to the early convective start I wound up getting into position barely ahead of the southernmost cell of a line of storms west of Lignum off Rte 3.  Looking back to the northeast I could see what looked like a wall cloud north of the Rappahannock River, but that cell was out of reach.

Choosing to stay in place I turned around to face southwest to watch another cell  approach with a distinctive lowering behind the leading edge, but I never verified any rotation even after viewing the video I took during its approach.

After the heavy rain and minor flooding passed me by I wandered along behind the line in Culpeper county until I noticed another updraft punching upwards.  So, I motored over to Rte 20 and headed south to the Locust Grove "Town Center" where I parked for about 45 minutes to watch as several cells developed on the end of the overall line.  I never saw anything severe, but I did watch an area of interesting scud for a while.

Finally giving up on the supposed second line I headed home through rush hour traffic just behind the above cell's rainshaft.  Overall I witnessed a few CGs, lots of rain, very little outflow wind, no hail, and no rotation...i.e. a garden variety Virginia thunderstorm day.  Good chase, nonetheless.