Monday, November 4, 2013

Just Because You Can Doesn't Mean You Should

As we move deeper into autumn, the atmosphere reaches into its bag of wintry tricks. The weather of last Friday provided an example of what Gordon Lightfoot called "the witch of November".

The driver was a deep low sited over northern Quebec that was wrapping up an impressive cyclonic flow. In the northeast and mid-Atlantic states a low level jet of air paralleled the associated cold front and furnished truly impressive winds aloft.

This wasn't an unforecasted surprise. The system could be watched for days as it crossed the continent and the meteorological models did an accurate job of predicting where all the pieces would be at the end of the week. Thus, I knew by mid-week that my usual trip from Connecticut to the DC area was seriously in doubt.

At left, a depiction of the wind field at 6,000 feet for about 20Z on Friday afternoon. You can see that the wind from the southwest was predicted to be about 60 knots over southern New England, falling off to 50 knots over northern New Jersey and "only" 40 knots over eastern Pennsylvania. If I decided to fly at that time I could expect (based on a true airspeed of about 135 knots) to achieve about 75 knots over the ground for the early part of the trip, and maybe as much as 95 knots as I approached Reading. I didn't think that would be any fun.

For what is usually about a 2 hour and 20 minute trip, the very accurate algorithm at FltPlan.com was predicting an enroute time of over three hours:

And just to complete the picture, the Friday morning Terminal Area Forecast (TAF) for Bridgeport was a bit sporty:
KBDR 011143Z 0112/0212 21018G35KT 5SM -SHRA BR SCT010 BKN020 
TEMPO 0113/0115 23025G40KT 3SM SHRA
FM011600 23014G25KT P6SM VCSH SCT020 SCT030 BKN080
FM012000 24012KT P6SM SCT050 
FM020100 VRB05KT P6SM SCT050=

For the time I'd consider departing, showers with gusty southwest winds would be on the menu, and the winds aloft would still be very strong. The good news: for the overnight period (after 01Z) there would be light, variable winds, good visibility and only a scattered cloud layer around 5,000 feet.

Hey, it's only wind. No convection in the forecast, freezing level up around 9,000 feet. I could make the flight. But as the wise adage says, "Just because you can doesn't mean you should." I decided to opt for a "Dawn Patrol" departure early on Saturday morning.

The forecast for 12Z Saturday morning showed the deep low moved off to the north, the cold front with its associated weather offshore to the east and a weak secondary cold front approaching from the west. I filed for an 0930Z departure (5:30 AM local) and asked for routing over JFK and south across New Jersey.

With the departure of the weather to the east and north, the winds aloft moderated quite a bit. From the depiction at left, the winds at 6,000 feet over New England and down to the mid-Atlantic were forecast to be mostly westerly at about 25 knots by 12Z. A lot better! So I set an early alarm and got myself to the airport by about 5:20 AM.

Now, fltplan.com was anticipating a half-hour less time enroute than the previous afternoon. However, I was disappointed (but not particularly surprised) to learn, when I queried the system before going out to the airplane, that ATC had assigned the usual eastern PA routing rather than the coastal route I'd requested. That would probably add 10 or 15 minutes, and it would force me up to 8,000 feet where I'd have to be careful about icing in clouds.

I seemed to be completely alone on the field. The control tower was closed until 6:30 AM. I pre-flighted N631S in the dark, and checked the weather. The automated weather system was reporting this:

KBDR 020952Z AUTO 02004KT 10SM BKN075 11/08 A2967=
A light wind from the northeast, good visibility under a broken ceiling at 7,500 feet. I started the engine and taxied to the hold short line for Runway 6. From there, I called New York Approach: "November 631 Sierra, on the ground at Bridgeport, looking for my IFR clearance to Victor Kilo X-Ray."

The approach controller read my clearance, asked which runway I'd be using, and released me for departure. N631S's wheels were off of the runway at 0957Z. After takeoff, she had N631S and I climb to 6,000 feet and headed us west. Soon we were transferred to the next sector and that controller said, "Skylane 631 Sierra, climb and maintain 8,000 feet."

Thinking there was no harm in asking, I said, "New York, 631 Sierra wonders if there is any chance for 6,000 as a final altitude."

The controller replied, "No, that's an 8,000 foot route. I can let you stay at 6,000 for another 10 miles but then you'll have to climb to 8."

I responded, "Thanks for that. I originally filed for 6,000 on another route; I was thinking there's a bit less headwind at 6.'

There was a pause. Then, "31 Sierra, did you file for a DIXIE route?" I said "Yes" and she replied, "Let me see if I can work that out for you. Stand by."

In less than a minute, the controller came back with, "Skylane 31 Sierra, we're working on a route for you. For now turn left to heading 190, vector to Kennedy, and I'll have your new route for you in a couple minutes."

Have I mentioned that I love Air Traffic Controllers? I thanked the lady profusely, and by the time I was across Long Island Sound and over Queens, she had an excellent clearance for me: radar vectors to DIXIE V16 ENO V374 OTT thence direct to destination. Trust me...that's a good one. The next controller put N631S and I direct to JFK and then direct to DIXIE. South of JFK the ceiling lowered a bit so we were in clouds at 6,000 but the air temperature was well above freezing.

New York handed me off to McGuire approach and I requested a descent to 4,000 feet hoping for a bit less wind (and hence more ground speed) and a better view below the clouds. That all worked out nicely and our passage through Atlantic City and Dover airspace was uneventful. Soon I was talking to Potomac Approach. Almost home!

Potomac said, "Advise when you have the weather at VKX." I said, "Wilco" and tuned a radio to the frequency for the automated system at Potomac Airfield. Three clicks on the push-to-talk switch gets you the weather at the field. But to my dismay, the robotic voice reported "Visibility one-half mile." Rats! VKX is in a small valley, and sometimes the fog does linger there. Getting back to the approach controller, I advised him of the situation and said I'd like to go have a look, and if conditions really were prohibitive for landing I'd have to divert or go hold somewhere. He said, "You can expect that."

Soon, I heard the Potomac controller say, to a pilot I couldn't hear, "Thanks for the pilot report." Then to me, "631 Sierra, did you hear that?" "Negative," I replied.

"A pilot who just departed from VKX said that it isn't nearly as bad as the automated system is saying." Great news! I said, "Thanks for that, I should be in good shape then." And I was. The photo at left was taken from the taxiway as I exited the runway after landing at 1210Z (2:13 enroute). As you see, there were just a few wisps of ground fog.