#vawx An equinox chase? Perhaps.

A cold front triggering severe weather across the eastern Plains and upper Midwest this Thursday evening just may provide a chase opportunity here in Virginia on Saturday, the autumnal equinox. Said front will slow down overnight Friday and sag south across the state as a backdoor cold front, setting the stage for a cold air damming event later this weekend.

This “wedge” front will settle west-to-east near the U.S. Route 460 corridor Saturday. This is the side-by-side comparison of the GFS (left) and NAM (right) forecast of the boundary’s location at 5 pm Saturday as evidenced by the dew point:

The GFS has the front a bit further north than the NAM at that time. Shear is forecast to be 30+ knots with CAPE (instability) at 1500+ j/kg, both decent but not ballistic figures of merit. The main question is whether this stalling seam between air masses can provide the lift needed to fire up robust convection as there won’t be much – if any – upper level support.

So Saturday is on the chasing calendar. That morning I’m sure I’ll be haunting surface observations (to find out exactly where the front is) and checking the short term models (to predict when and where storms may fire). Gotta take advantage of these late September opportunities as the 2018 chase season winds down!

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#vawx Missed this one

How ironic is this? Today is the 14th anniversary of the tornado outbreak across Virginia from the remnants of Ivan and what happens?SPC storm reports Sep 17 2018

The remnants of Florence certainly packed a punch for the Old Dominion today with at least one fatality and significant damage in the greater Richmond metro area. I didn’t give chase for a couple of reasons:

(1) The most vigorous storms rolled through Southside VA early today, with a confirmed tornado occurring in Mecklenburg county just north of Clarksville around 10:30 this morning. The axis of the convection was along and east of the U.S. Route 501 corridor and the storms were scooting north-northeast. I’d have been in an early morning (and mostly futile) tail chase from the get-go.

(2) The counties between me and the storms were blanketed by flash flood warnings from heavy overnight rainfall. The main roads were probably OK but storms don’t follow the main roads. Also I would have had to traverse the flooded areas going to and coming back from chasing these storms.

I had hopes of more strong convection firing over the mountains and moving east of the Blue Ridge before dark but that didn’t happen. A scattered line of cells did go up along and east of the U.S. Route 29 corridor but they haven’t amounted to anything as of the time I’m writing this. So I was out of position today while chasers further east were in the drivers’ seat.

So chalk today up to a missed opportunity for an awesome chase but not so great a day for those affected by Nature’s rampage.

 

#vawx Early timing and too much water may well deter a chase today

I didn’t head out to chase the action along and east of U.S. Route 501 this morning despite a couple of tornado warnings in that area. The truly daunting part that held me back was the sheer number of flash flood warnings that are still in place even at the noon hour. Chasing tornado-warned storms is tough enough without having to deal with flooded roadways.

Anyway here’s today’s SPC convective outlook and a related MD in effect as I write this:

The MD text only mentions a 5% chance for a watch being issued so there’s that. Meanwhile I am waiting for more convection to cross the Blue Ridge south of Roanoke late this afternoon. If that activity looks robust enough and IF it arrives before dark I’ll roll down the driveway. Hopefully any flooded roadways in that area will have had time to clear before I get there.

But overall it’s highly likely that I’ll leave today’s chasing to folks nearer the I-95 corridor.

#vawx To chase or not to chase Monday?

Still think tomorrow (Monday 9/17) will have interesting chase parameters as shown in these two forecast summary graphics. First, the GFS SCP forecast:GFSMA_con_scp_027

Then the 3 km NAM STP forecast:

NAMNSTMA_con_stp_026

Both of them are encouraging as is the outlook for more cellular (vs. widespread) rain tomorrow. The main fly in the ointment will be the number of roads affected by flooding. I’ll have to be very judicious on when and where I go as traveling on back roads won’t be very smart tomorrow.

Decision to chase? TBD.

#vawx A tropical remnants chase Monday?

There are still a lot of moving parts to the forecast for Hurricane Florence but, to reiterate, I don’t chase tropical systems. That being said I do keep an eye on the dissipating remnants of such systems to determine if there is potential for rotating cells on the eastern side. Thus this NHC forecast track for Florence’s remnants caught my attention:093018_5day_cone_no_line_and_wind

With the storm’s center forecast to swing west across the Carolinas and then north possibly on the other side of the Appalachians I wondered if there was potential for chaseable storms here in Virginia Piedmont. Thus I dutifully checked the GFS and found this for Monday afternoon:

Both the 0-3 km EHI and the supercell composite outlooks for Monday afternoon could tempt me to chase if this setup continues to hold true. We’ll see.

Meanwhile my thoughts and prayers are with those who are displaced and whose homes and livelihoods are threatened by Florence. That’s the more important story here.

#vawx A chase squeezed between two fronts

Saturday September 8th’s chase was a tale of two fronts. The first had slid south of the Virginia/North Carolina state line and was parked down that way. The second was a backdoor front that pushed southward across Virginia the entire day, ushering in a cold air damming wedge with temperatures in the 60s behind it. No widespread severe activity was anticipated but the short range models indicated chances of rotating storms along the wedge front itself. Thus I picked up my chase partner at 2:30 and motored eastward.

Given seemingly schizophrenic model solutions (one set showed strong convection beginning over U.S. Route 460 and moving south while another set held fast to convection firing along the state line and moving north) we split the difference and headed to Gretna along U.S. Route 29. Regrouping there we decided to roll north to a park in Altavista to watch and wait.

After cooling our heels at the park for a bit I noticed a slowly intensifying storm just north and east of town. Under the well-defined base I could see a semblance of a lowering so we made our way back to Rte 29, heading north on that high speed path and then turning east onto the Gladys road to intercept the cell. When we ran under the back edge of the precipitation shaft we dropped south on more rural roads and wound up with this view of the growing complex to our south.Altavista cell from the north

The southwestern edge of the cell showed signs of a flanking line building both visually and on radar.

We thus made the command decision to get south of this action and chase it. Winding our way further eastward to U.S. Route 501 we scurried south through Brookneal as I could see what appeared to be a flat mesocyclone base under the updraft. Continuing south to Volens we turned northwest on the Cody Road and stopped at a known vantage point in the Republican Grove vicinity. This was our view looking north from there:meso from Rep Grove vantage point

Not satisfied with the view from here we maneuvered around a bit before stopping at a site somewhat south of the Republican Grove area. This was the radar view about the time we stopped to observe again:

From here we watched as the storm base slowly trudged by just to our north showing signs of the meso evident on radar.meso base near Republican Grove

We continued south from here when the rain approached and stopped at one more rural site. By this time the complex had stretched east and west quite a bit and the convection was exhibiting the smooth surfaces of cold air intrusion. It was thus apparent we were watching convection build along the wedge front itself. When the rain neared again we pushed southward along more rural lanes to VA Route 57 to gain distance between us and the front.

With more convection firing near South Boston we diverted east toward Halifax and stopped at an open spot just east of town on VA Route 360. Storms were building literally 360 degrees around us at this point. This was our last peek at the westering sun before we gave up the chase and drove west toward Danville as rain filled in all around.sun peeking thru from Halifax vicinity

I have yet to review the dashcam videos from this chase but there was little real-time visual indication of rotation. But overall it was a successful storm intercept with enough activity to hold our interest for the afternoon.

#vawx Local chase for the first day of meteorological autumn

With yet another day of no cap, no shear, and slow-moving heavy rainers I wasn’t excited enough to stray too far from home base. But when storms came calling just after lunch I rolled down the driveway at 1:30 to check out the action over the Roanoke valley. Other than some CGs and multiple rain shafts there wasn’t much to gloat about from my local vantage point.

However upon turning around toward the north to check out another cell I spied a suspicious lowering that begged for a closer look. I dutifully hopped back in the chasemobile and gave chase, driving north up U.S. Route 11 through the metropolis of Troutville to get ahead of the growing rain shaft. With the precipitation not very far to the west I found an open spot at the Troutville Elementary School where I had this view of the lowering:feature approaching elementary school

This was a couple minutes later when the feature was a bit closer:

second look at feature over school

It was likely just persistent scud on the leading edge of the storm’s outflow but it did pique my interest. There was also greenage evident but I couldn’t linger long outside the vehicle as CGs sizzled down too close for comfort.

After a very few minutes I pulled up stakes and sped north on Rte 11 to escape the onrushing rain. A few miles further north I pulled off the highway into a hilltop graveyard that afforded a good view of the approaching storm:Storm approaching graveyard

This was the radar depiction at the time:

As shown in the velocity scan I was parked in what could be considered a weak inflow notch but I didn’t visually recognize any rotation.  The heavier precipitation – and possible hail – passed by me to the west, just on the other side of I-81.

One of the final views before the rain hit:scud over graveyard

After conducting a “static core punch” I called off the chase and motored south toward home, satisfied that I’d squeezed everything possible out of this local adventure.

#vawx A truly marginal day for chasing

With a “cold” front oozing across the Appalachians and bumping up against a very hot and humid late August air mass I thought today might be a possible chase day despite the lack of shear or a cap. The SPC seemed to agree:VA_swody1

With that graphic in mind plus a detailed review at short range models I picked the U.S. Route 460 corridor as the best convergence zone for convection. With updrafts going up early over the eastern slopes of the Blue Ridge I was tempted to head to the Martinsville vicinity instead. Indeed, that complex went severe-warned as I rolled toward Bedford but I was willing to bet that it would rain itself out given no cap and very little shear. I was right…about that cell, at least.

After filling the chasemobile’s gas tank I wriggled my way through Bedford to a rural spot north of town in order to intercept a nice-looking storm on radar that looked to cross the mountains from near Buchanan. When that cell weakened and stopped building on its southwestern flank it drifted more north than east, away from my vantage point. I then dropped south of town on VA Route 122 to another spot in Bedford county to settle in and observe convection down that way.

Unfortunately that activity also quickly waned. This cell pulsed up just west of my location but then rained itself out as it passed overhead:Bedford county cell

I retreated back north to a park in Bedford where I cooled my heels for quite a while, watching radar and waiting. Everything east of the Blue Ridge was pulsing and raining out, leading to a typical late August game of “whack-a-mole” for chasers. I did notice that convection west of Roanoke was moving slowly north-northeast but was persisting. Thus a bit after 4 pm I made the command decision to ignore yet another group of cells growing just south of Lynchburg (figuring they would also pulse up and quickly rain themselves out) and push back west to check out the longer lasting action.

That was a mistake. Here’s that complex along U.S. Route 29 that not only held together over Lynchburg but went severe-warned:

Meanwhile the northern end of the western complex which I observed from near Daleville pushed out a brief shelf cloud that quickly fell apart:Botetourt shelf cloud trying to form

Finally bailing on this action I grabbed a sandwich to take home but was diverted by storms from the southern sections of the same complex as they crossed the  Roanoke valley. I wolfed down the sandwich while watching these storms.

This action crawled northward toward me at a snail’s pace and just before I finally called it a day this feature showed up between two separate cells:Feature over Roanoke

There were indications of weak rotation on radar at this junction between two storm bases but it wasn’t enough to tempt me to stay and let the rain wash over me. Thus I headed home and let the soggy southern section of the activity – responsible for flash flooding southwest of Roanoke – crawl  eastward across the Blue Ridge without my participation.

It was a late August non-tropical chase. That explains a lot.

#vawx A nine year anniversary of a surprise funnel

Today brings back a memory from 9 years ago. This surprising funnel dipped down near Fredericksburg VA on a very non-descript chase day.

The visibility through the late August haze wasn’t good but the funnel was obvious from this vantage point in western King George county looking to the southwest. There were no warnings issued on this storm so I doubted what I was seeing for a bit, thinking it might have been just scud. Nope, it was a persistent funnel!

The spooky thing was that I’d witnessed another surprise funnel from this same spot and in the same location exactly 3 months earlier on May 28th. These features must have occurred below the NWS Sterling radar horizon and were likely fostered by very localized conditions (e.g. low level shear) in the Rappahannock River valley as it widens abruptly east of the fall line.

#vawx Haven’t had a total bust for a while until today

Today, Tuesday August 21st, was a certified B-U-S-T for both my chasing and the SPC Slight Risk shown here:VA_swody1 (1)

After reviewing several different models and model runs this morning I was certain this Slight Risk was overkill for areas of Virginia south of I-64. As of 8:40 pm (as I’m writing this) there have been no tornado or severe thunderstorm warnings issued south of that corridor so I suppose I was correct.

I did think that some upper level support (500 mb vorticity and resulting 700 mb vertical velocities) shown on both the GFS and RAP would result in storms east of the Blue Ridge before dark. That plus several short range model solutions showing strong convection by late afternoon convinced me to target the Henry/Patrick county area of southern Virginia. I rolled out a bit earlier than planned when some showers went up over Roanoke just after lunch and made my way toward Patrick Springs on U.S. Route 58 west of Martinsville. A line of strong convection along the North Carolina mountains was heading in that direction and I hoped to intercept the action coming across the state line.

After cooling my heels near Patrick Springs for a while I conducted a little rolling reconnaissance southward into the Tarheel State. To put it succinctly the chase territory south of the state line in that vicinity stinks. The area is pretty with rolling hills and winding roads but neither of those parameters make for good chasing. By the time I returned to Patrick Springs both the radar and MK 1 eyeball scans indicated that the formerly strong convection had fallen apart. Sighing heavily I motored back toward Rocky Mount via U.S. Route 220 to see if another line slowly trudging in that direction would supply any excitement. Nope. That fell apart as it crossed the Blue Ridge.

Thus I had an unusual early dinner in Rocky Mount before traveling back home. And to cap off the frustration of a bust another convective line strengthened as it rumbled its way through the neighborhood near sunset.

So what happened? My hunch is that the trough didn’t deepen as much as the models predicted so the upper level temperatures were higher and thus the mid-level lapse rates were woefully weak east of the Appalachians. The updrafts that I could see looked very anemic. Also I don’t think the 0-6 km shear was as strong as advertised south of I-64.

BUST.