Shifting model solution

It now appears that - rather than Monday and Thursday - we will see cold frontal passages through here on Sunday and Wednesday of next week. The one on Sunday won't have much to work with for rain or storms, but Wednesday's event looks to have some convective potential (CAPE forecast shown above) associated with it. The winds show some speed shear but not much directional shear as of this morning's model run, but I'll take what I can get if it means a chase!

No joy today, but NC got hit yesterday

I was correct about the SPC downgrading the severe risk for our area from the "See Text" they had us under. With the more southerly route taken by the upper level low we have remained in a more stable regime than originally forecast, so chasing was not in the cards today. Next couple of potential opportunities will be next week (Monday and Thursday???) so my gear will stay in the corner for another week.
Meanwhile several tornadoes touched down in North Carolina yesterday, leaving me envious of the chasers in that area but sorry that folks suffered from the storms. That's the chaser's dichotomy: excitement about the chase mingled with horror at the devastation. The good news is that ground truth reports by chasers have provided the NWS with more data to issue better warnings about severe weather.

Maybe, maybe not tomorrow

One thing you can count on this time of year: the models have a hard time adjusting to the dynamic conditions of spring. Thus I wasn't really surprised - maybe a bit disappointed - to see that the forecasts for tomorrow's potential convection had changed significantly since yesterday. The upper level low that in turn will force a coastal surface low to form has been shifted south in the latest model runs, resulting in our area remaining under more stable conditions while the convective potential shifts southward into the Carolinas. The SPC still has us under a "See Text" for tomorrow, but I wouldn't be surprised to see that change as well. Still, I'll be prepared to chase tomorrow afternoon in case the sun comes out soon enough to destabilize things before the dry air behind this system gets in here.

Monday afternoon storms

The local NWS forecast doesn't mention thunderstorms for Monday, but both this model and others show a modest amount of instability in our area from a surface low pressure system that is forecast to transit southeastern Virginia that afternoon. Also, after I checked out these models this morning I glanced at the SPC convective outlooks and found a "See Text" (5% severe probability) outlined for Virginia east of I-95. If the sun can peek through Monday afternoon we might see some chaseable storms, so I'm going to work prepared to keep one eye on the radar. Maybe another March chase!

Northern Madison county rain free base

This video, sped up 4 times, shows the rain free base I was observing yesterday from a position just off Rte 29 south in northern Madison county. Note the cloud motions in the foreground (left to right) versus the almost static features in the background. This is a visual indication of the rotation on this cell. That, coupled with the scud rising into the base, was the beginning of the conditions that led to the severe TS warning issued on this storm a half-hour or so after this point.

First Chase!

Given the forecasts - including a 5% "See Text" from the SPC - and surface conditions today I decided at noon that chasing was worth a try. There were storms east and west of I-95 at that point, but the sky was clearing west of I-95 and was a better bet for discrete storms that I could actually see rather than being caught under the mushy overcast further east. So I headed out for Culpeper to intercept a growing line that was actually heading northwest, which was a bit weird, but they were pivoting around the upper level low out west. I stopped in Culpeper to update my situational awareness via a WiFi link since I am currently sans internet air card (a situation I plan to remedy next month). Radar showed me to be in "no man's land": there was a so-so storm to my southwest and a better storm to the east, but I couldn't make both of them...a typical chaser's dilemma. I decided the storm in Madison county was the better option so I dived southwest to catch that one, stopping off Rte 29 to see this:
The storm was moving left to right and I wanted to get closer as well as a better view so I left the main roads and wound up taking an excursion on the back roads of Culpeper county. I could catch tantalizing glimpses of what appeared to be a fully developed wall cloud but I never found a tree-free vista to stop and look until I wound up on Rte 522, stopping just north of Griffinsburg to witness this:
This picture was taken a few minutes after the following doppler radar frame which indicates rotation on the base of the cell:
I observed for a few minutes as "my" storm escaped over the Blue Ridge, and then I motored back to my WiFi spot in Culpeper only to find that a very nice hailstorm was pounding the countryside within spitting distance of my house. Grinding my teeth since I knew I couldn't catch it (most cells had an average ground speed of 30+ knots) I stopped in a favored viewing spot east of Culpeper to watch a small line pass by with low-topped but rotating towers. Nothing else happened so I pulled up stakes and headed home, arriving to find yet another very nice storm pushing through Colonial Beach and Dahlgren...again, just out of my reach as I couldn't have intercepted before it crossed the Potomac River. So close, yet so far!!

Perhaps a March 2010 chase isn't out of the question

Latest model runs show enough instability and moisture coupled with upper level cold air to cause the SPC to issue a "See Text" 5% probability for severe weather in our area on Monday. The text discussion mentions mainly a hail threat for us, so I'll be primed to head out tomorrow afternoon pending what I see on the short range model forecasts and the local radar pictures. Fingers and toes are crossed!

Not Sunday...maybe a boom or two Monday

The chances of squeezing in a March chase are dwindling. The models have consistently slowed down the approaching system to where the most rain will now be on Monday, and the surface low pressure is forecast to cross our area directly overhead. That will mean overcast, no sun, and only a slight bit of CAPE. Thus we may see a thunderstorm or two but it will likely not be a chaseable event. Another system approaches us later in the week, but at this point the chances of decent convection are doubtful. SDS is reaching a fever pitch here!!

Sunday?

The longer range models are converging on a solution that shows a cold front pushing through the Mid-Atlantic on Sunday afternoon. The moisture return is weak with dewpoints only in the 50's, but the upper level winds at both 850 and 500 mb will be pretty strong so there will be a lot of forcing available. The one ingredient missing is a forecast for sunshine to allow the strong March sun to destabilize the lower atmosphere and initiate convection. If we could get a few peeks of sun Sunday afternoon the CAPE values would skyrocket and we might see a few decent boomers. The shorter range models will be chiming in by this time tomorrow, so I'll be keeping one eye on all possible forecast solutions and the other eye on both the SPC and the local NWS forecasts. I need a March chase to alleviate rampant SDS!!!

Thunder and lightning last night, more next Sunday?

We had a decent convective line plow through here just after midnight last night, providing the first thunder and lightning of the 2010 season. Given the above graphic for next Sunday there may be potential for a chase that afternoon. The model graphic shows us to be in the warm sector of a system that is poised to send a cold front blasting through the region that afternoon. The upper level support seems to be pretty far north, but if enough moisture and temperature contrast is available we could see some convective storms (crossing fingers...).

No chasing this week

It seems that the models are losing enthusiasm for convective instability in our area this weekend, so my hopes for a Friday or Saturday chase are quickly dwindling. The cut off upper level low is apparently going to swing through here with heavy rains and overcast late Friday and during the day Saturday. I'm still keeping my fingers crossed for a March chase or two, but it won't be this week.

Cold core tornadoes in Oklahoma

The upper level storm system out in the Plains produced at least one photogenic tornado captured by stormchasers today in a cold core setup, meaning an upper level cold pool of air created enough instability coupled with the vorticity - "spin" - from the tightly wrapped low pressure system to create tornadic conditions. That same storm system is headed east and will drag moisture and some instability into the Mid-Atlantic later this week. The GFS model is still indicating some potential for thunder Friday altho' the potential continues to jump around from run to run. Will there be the first chase of 2010 this week? Don't know for sure yet, but it beats waiting out another snow storm!

Waffling back toward Friday

This morning's GFS model run looks better for convective potential next Friday afternoon, altho' the dewpoints look a bit low. There's still a lot of number crunching that is to happen before then plus a lot of other models to check so I'm not allowing myself to get too starry-eyed about chasing Friday. But then, I'm not giving up on it either! Several previous Virginia chase seasons have begun in March so it's not out of the question that Friday could prove productive.

March 16th Tornado Drill

F3 tornado Remington VA 17 Sept 2004

The Virginia Department of Emergency Management (VDEM) conducts an annual tornado drill to train folks what to do should a tornado approach your home, school, or place of business. Since recent years have brought strong tornadoes to Virginia (17 Sept 2004 F3 in Remington, 28 Apr 2008 EF3 in Suffolk, 8 May 2008 EF2 Rte 17 Stafford county) and since I've personally witnessed a number of otherwise unreported funnels and tornadoes in the Fredericksburg area, it would be worth considering signing up for this event, which will occur statewide at 9:30 a.m. on March 16th. The aforementioned website contains a link to a registration sheet to become an official participant in this year's drill. Sign up and take part in this important safety training event!

CAPE encroachment

Convection is getting closer to us! This is the forecast mixed layer CAPE (convective average potential energy) for next Friday afternoon, showing some instability in southeastern Virginia. Actually last night's model run had us under some instability, but this morning's run pushed it southward due to what looks like some cold air damming. Two things however: (1) It's getting closer to chase season! and (2) models can jump around a lot this far out. Can't wait!

Andover Kansas 1991 F5 tornado

Two videos of the 1991 devastating Andover Kansas tornado just became available on the Web. This is a classic F5 tornado that is still being studied. The first video is of the tornado's approach to a subdivision, and the second video is of the incredible aftermath. Since Virginia's tornado drill day is fast approaching on March 16th I thought this was apropos to post them, but I've since found out that the first video seems to be restricted to those with a YouTube account. Check out the second video anyway.