Saturday, August 22, 2009

Well, THAT was interesting!

In Friday afternoon's post I commented that the weather was looking none too good for my usual trip to DC. That turned out to be a bit of an understatement. When I got to KBDR at around five o'clock the squall line was just to the west and the sky looked like this:

A number of aircraft headed for White Plains (KHPN) had taken refuge at Bridgeport and I joined their flight crews in monitoring the radar depiction as the line passed through. The rain began at 2133Z. We saw heavy rain and winds gusting to about 25 knots. Then the fast-moving line moved on and by about 2200Z it was pretty much over. N631S and I got off the ground at around 2225Z. There was still some weather over northern New Jersey but the normal routing out to SAX and down to SBJ, thence to the west, avoided most of it. A look at the Garmin GPSmap 396 weather picture at 2242Z looked like this:

Bear in mind that this line was moving rapidly east. I never did get involved with the patch of yellow "moderate precip" seen in the screen shot above.

Once I was clear of the interesting weather in the New York area I turned my attention to the situation down near my destination. That came as a a bit of a shock. If you look back at the regional radar picture from Friday afternoon you'll see a small line of activity down in West Virginia, well south of and separated from the major line I'd been worrying about. Well, that stuff came down out of the hills and exploded! It turned into a large area of convective weather moving slowly eastward with an ETA at Baltimore about the same as mine. Clearly it was time for a Plan B. So as soon as Allentown Approach handed me off to Harrisburg Approach, I requested that they coordinate with Potomac Approach to re-route N631S and I around the western side of the Washington Class B airspace. Withing a couple of minutes I was cleared, "after Lancaster, direct SCAPE, direct Hagerstown (HGR), direct Martinsburg (MRB), direct". By 0013Z, as darkness descended over the Pennsylvania landscape, the routing looked like this:

It was obvious that the part about "MRB, direct" wasn't going to work out but I accepted the clearance knowing that I could get a re-route down the road. Sure enough, as I approached Martinsburg I received a change to my routing: "After MRB, direct Casanova (CSN), direct Brooke (BRV), direct." More better.

This looked like I could go around the southern end of the weather and access VKX from the southwest via the RNAV 6 approach. Soon thereafter, the Potomac Approach controller began giving me vectors to shorten the route to VKX and then cleared me direct to the initial approach fix (the IAF) which is WOBUB. Let me jump ahead just a bit and show you the entire 3.3 hour flight courtesy of FlightAware:

If you click on that last picture to enlarge it, you'll see a piece of weather just to the southwest of VKX, with the flight track passing right through it. I'd been watching this cell for some time. It was moving slowly to the northeast and I knew I'd be close to it. I had talked to the Potomac Approach controller about it -- he said it showed up on his radar as moderate to heavy precipitation and it appeared that I was going to go right through it. I was at 1,700 feet MSL at the time, and looking out my windshield I could see the edge of the precipitation and could see that I would pass just clear to the northwest of it. To give myself a little more margin I asked the controller if I could bypass the IAF and go direct to the next waypoint on the approach. This allowed me to stay visual and keep my runway in sight. He cleared me for that and I landed at VKX without difficulty.
I believe that was another instance of the difference between a composite weather radar image (showing the most intense precipitation at any altitude) and the actual conditions at a particular altitude (e.g., the "base"). I've blogged about this in the past.
In any event, I was on the ground at 0145Z for 3 hrs +20 min en route -- much longer than the typical trip. It was good to be home.

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