Thursday, October 28, 2010

Go Where the Weather Isn't (cont'd)

The previous post discussed the merits of planning one's route to go where the weather is not. This is such a self-evidently Good Idea that it seems even the airlines do it!

This week we had as a house-guest for a few days a young lady from Europe. On Tuesday she was headed on to Seattle and we took her to KDCA for her flight, Alaska Airlines Flight 3. Our young friend expressed the hope that her flight would not experience much turbulence. I was aware that the middle of the country was enjoying a day of very energetic and unpleasant weather, so I was minimally reassuring.

Alaska Airlines' Dispatcher for Flight 3 was contemplating the same weather system, and this (courtesy of FlightAware.com) is the solution that he or she came up with:

Pretty slick. A good example of the shortest distance between two points not being a straight line (or, in this case, a great circle course). And it's equally true for a Skylane or a 737-800. Of course, we get the fun of being our own Dispatcher.

Tuesday, October 19, 2010

Go Where the Weather Isn't

Better late than never, I'm finally getting around to a post about the flight last Friday from KBDR to KVKX. You might recall that some fairly enthusiastic weather came up the coast on Thursday. By Friday afternoon a deep low was churning up the Gulf of Maine and some continuing weather was wrapping around the back side and descending into lower New England.

I'd been watching the development of the system (first discussed here and then here). Now it was time to deal with it.

The freezing level was predicted to slope from 8,000 feet over North Carolina down to 4,000 feet over Massachusetts. I was concerned that the usual ATC preferred route (west to Pennsylvania then south, at 8,000 to pass over the KEWR arrivals) would encounter icing, so I filed for a route across JFK and down through New Jersey at 6,000.

By 18Z, things were looking promising. At left, the view from my office parking lot, with a broken deck at moderate altitude, clear above. The airport was reporting that ceiling at 4,400 so it looked like punching through the layer to clear conditions could be a viable approach.

Of course, I got an e-mailed notification from FlightAware.com that ATC was intending to issue the "usual route": SAX V249 SBJ V30 ETX V39 LRP V93 BAL direct. They wanted me to go where the weather was and I wanted to go where it wasn't.

At left, the radar picture (base layer) at 2025Z, roughly my time of departure. The composite looked scarier. Between the radar picture and what I could see from my window, I really didn't want to go to the west. So when I finished pre-flighting N631S and was ready to go I called Bridgeport Clearance Delivery:

N631S: "Bridgeport Clearance, Skylane 631 Sierra IFR to VKX; you're going to read me a clearance that starts with "radar vectors to Sparta." I'm going to be unable to accept that due to icing conditions on that route. I need something that starts with "Vectors to Deer Park, thence Victor 16."
KBDR Clearance: "31 Sierra, you want to go V16 over JFK?"
N631S: "Affirmative."
KBDR Clearance: "OK, stand by, let me talk to them."

I'd been here before and wasn't very optimistic about New York Approach being in a cooperative mood. They really want the southbound traffic to swing out to the west. But as the minutes passed, I started to be a bit hopeful. After all, it doesn't take any time at all to say, "NO!" Sure enough, after ten minutes I heard:

KBDR Clearance: "31 Sierra, we've got it, just give me a couple more minutes to work out the other end of the route," followed two minutes later with, "31 Sierra, advise ready to copy."
N631S: "31 Sierra, go ahead."

The clearance I got was: Vectors to DPK V16 DIXIE V1 ATR V308 BILIT direct DCA direct. The back half of that would have to be re-negotiated en route - there was no way that Potomac Approach would let me go to DCA, and Waterloo (ATR) was out of the way - but the front half served to get me outta town. Sold!

The METAR in effect at KBDR when I took off was:

KBDR 151952Z 27020G29KT 10SM FEW040 BKN110 13/05 A2936 RMK PK WND 31033/19270
20 knots of wind gusting to 29 is fairly sporty, but it was nearly aligned with Runway 29 and so not a problem. The lower cloud deck had opened up to "few at 4000" above the airport, but I could see more solid cloud coverage to the south.

I was happy to find that my assigned altitude of 6,000 feet initially put me on top of the cloud deck. By the time I got to JFK the tops had risen a few hundred feet so that I was in and out of the layer. The temperature aloft was 30F but I was never in the clouds long enough to accumulate any ice.

In due course, New York Approach handed me off to McGuire and McGuire handed me off to Atlantic City. It was time to do something about that clearance.

N631S: "Atlantic City Approach, Skylane 631 Sierra, request."
A.C. Approach: "31 Sierra, go ahead."
N631S: "My current routing has me going by way of Waterloo and DCA and I know Potomac Approach doesn't want me going to DCA. Can you work out something like after LEEAH, V268 to Smyrna then V379 to Nottingham thence direct?"
A.C. Approach: "31 Sierra, let me talk to Dover and see what they're willing to do."

A.C. Approach was back in five minutes with a re-route: Present postion direct ENO V16 CHOPS V308 OTT Direct. OK, I liked it. The red line on the chart clip above at left (courtesy of Skyvector.com) is my original routing. The blue line is the re-route. One of the nice things about the blue-line route is that it avoids a fairly long leg over water going down to Waterloo (ATR). I will do single-engine over water beyond gliding distance to land, but I never like it.

The balance of the trip was uneventful. And once again I am appreciative of ATC's professionalism and flexibility, essential to making this flight on a day with interesting weather.

Monday, October 18, 2010

4,000 Hours

Not me...the airplane! This morning, a bit less than an hour after departure from KVKX en route to KBDR, the tachometer rolled to 4000.0 hours. This, exactly 33 years and 7 months from the date - 18 March 1977 - that N631S first rose from a runway into the sky over Wichita.

Looking back at the logs, I see that the first 1,000 hours took about six years, as did the second. The third 1,000 hours took 12 and 1/2 years and the last thousand took nine years. Over the years, the aircraft has built time at an average rate of 119.1 hours/year. N631S has been with me since late September of 2004; since then we've flown 755 hours together.

It's interesting that the Vref aircraft valuation service provided by AOPA says that the fleet average total time for '77 Skylanes is 3960 hours; as of now N631S is almost perfectly average.

N631S is, to me, a nicely-broken-in airplane in the prime of its life. With continued good maintenance and a pattern of regular use, 31 Sierra can look forward to many more years of reliable usefulness.

Thursday, October 14, 2010

Marginal Weather

The weather remains less than encouraging. At this writing (0030Z) it is raining zealously here in Connecticut and the forecasts are marginal at best. To begin with there are these Terminal Area Forecasts (TAF's) for Bridgeport and Washington National:
KBDR 142352Z 1500/1524 04010KT 2SM +RA BR BKN015 OVC025 
     FM150400 34010KT 5SM -RA BKN015 OVC040 
     FM150800 32013G20KT P6SM SCT015 BKN040 
     FM151500 30018G28KT P6SM BKN040 
     FM151800 29020G33KT P6SM BKN040
KDCA 142329Z 1500/1524 33009KT P6SM FEW080 SCT250 
     FM150600 27010G18KT P6SM SCT060 
     FM151300 28010G20KT P6SM SCT060 
     FM151600 30015G25KT P6SM BKN060 
     FM152200 29010KT P6SM SCT250
For a 21Z departure, the southern end of the trip would be fine but the departure presents issues. The surface winds will be sporty, 20 knots gusting to 33 from the northwest, but that's not the problem. The problem is the 4,000 foot ceiling considered in light of the anticipated freezing level. Here's the latest on that:

At left, the forecast temperatures at the 800mb level at 00Z tomorrow (about 6,000 feet MSL). As noted in the previous post, the 8,000 foot routing over eastern Pennsylvania just isn't going to work. In fact, unless actual conditions are better than the current forecast, 6,000 feet over JFK is also not likely to work. What I really need is 4,000 feet over JFK and I rather doubt that New York Approach will be happy to give me that.

So here's Plan A: File for 6,000 over JFK thence Victor 16 down through New Jersey, and if the 18Z weather says that is unwise, refile for 4,000 and see how ATC feels about that. Plan B would be to depart VFR and fly to New Jersey via the Hudson River Skyline Route at about 2,500 feet, proceeding to Toms River (KMJX); land there and file IFR at 4,000 feet from there to KVKX.

And, I guess, Plan C is AmTrak.

Wednesday, October 13, 2010

'Winter Is Icumen In'

Winter is icumen in,
Lhude sing Goddamm,
Raineth drop and staineth slop,
And how the wind doth ramm!

--Ezra Pound (1915)

Looking ahead to Friday's weather has me in an unhappy mood. Here is a picture of the reason for my discontent, courtesy of NOAA's Aviationweather.gov:

This shows the forecast for the 850mb pressure level (i.e., about 5,000 feet MSL) on Friday evening at 00Z. It's based on the NAM model run at 18Z today. The precipitation data is for the period from 18Z to 00Z and the blue curve is the 0 degree C isotherm. (If you click on the image you'll get to see the uncropped version.)

With my usual departure time from Bridgeport's KBDR of around 21Z, it doesn't look like I'll be dealing with much precipitation. But I anticipate low to medium ceiling heights and a fairly low freezing level (reference that 0 deg. isotherm). It seems unlikely that the "usual routing", at 8,000 feet over to Sparta and Allentown, will work due to probable icing conditions. I might get away with a route over JFK and down the New Jersey coast at 6,000 feet. If I can get my friends at ATC to clear me that way.

If ATC is uncooperative, I might (as a last resort) be able to file to an intermediate destination in New Jersey (possibly KMJX, Miller Airpark in Toms River), land there, and refile to KVKX from that point. That would probably game the system but it's irritating to have to contemplate such subterfuge.

We shall await developments...

Friday, October 8, 2010

Bernoulli vs. Newton

Today, at the wonderful XKCD:
(When you click on the image, be certain to "mouseover" and read the alt text.)

Thursday, October 7, 2010

No Surprises

The weather at departure from KVKX on Monday was wet, as anticipated. The NEXRAD radar image at left was recorded at 1151Z, just about the time that N631S and I were lifting off. Widespread light showers were the order of the day. The conditions at National Airport and at Andrews AFB were:
KADW 041149Z AUTO 35013KT 8SM RA OVC005 10/10 A3009 RMK AO2 CIG 004V007 SLP193
KDCA 041147Z 35012KT 2 1/2SM RA BR BKN014 BKN022 OVC038 11/09 A3012 P0002
For once, conditions at KVKX were closer to those at KDCA than KADW. On climbout, N631S entered the overcast at about 1,200 feet, well above the 500 foot ceiling Andrews was reporting.

After that it was pretty much in the schmoo until the clouds broke up at 7,000 feet over Dover AFB. For the trip across New Jersey it was entirely VMC between the layers, with lots of sunshine, until arriving in the New York area. There was another area of thick clouds and precipitation over Long Island. The rain didn't extend across the sound into Connecticut but the cloud cover did. The image below, from 1350Z, shows the extent of the precipitation at arrival.

So N631S and I descended through the clouds over JFK and were vectored for the ILS approach to Runway 6 at Bridgeport. We broke out of the overcast at about 1,500 feet, a few miles from the threshhold. The surface wind was gusty but from the northeast in line with the runway, and the landing was uneventful.

The folks at NOAA's National Climatic Data Center (NCDC) have a new Beta version of their Weather and Climate Toolkit available here. It has the ability to integrate Google Earth imagery with historical NEXRAD data (I've blogged about the historical radar image tools in an earlier post). The radar images above are examples - I think it's pretty cool!

Sunday, October 3, 2010

Another Rainy Monday

Looks like another rainy Monday morning in store. At left is a clip from the 24-hour forecast map from the NCEP site, valid at 12Z. As I plan to depart KVKX (in the DC area) about that time headed for KBDR (Bridgeport, CT), I anticipate a damp flight. From the position of the low I also expect headwinds due to the cyclonic flow.

For departure conditions, lets look at the Terminal Area Forecasts (TAF's) for Washington National (KDCA) and Andrews AFB (KADW).

KDCA 031739Z 0318/0418 04012KT P6SM BKN028 BKN040 OVC060 
     FM032000 02010G17KT P6SM -RA OVC025 
     FM040100 02011G18KT 6SM -RA OVC020 WS020/04035KT 
     FM040500 36015G21KT 5SM -RA BR BKN012 OVC020 
     FM040900 35013G20KT 4SM -RADZ BR OVC008 
     FM041400 33012G20KT 5SM -RA BR OVC009
KADW 0317/0417 03010G15KT 9999 BKN020 OVC030 QNH2997INS 
     TEMPO 0317/0320 SCT020 OVC030 
     BECMG 0405/0406 36012KT 4800 -RA BKN010 OVC020 QNH3000INS 
     BECMG 0412/0413 35012KT 9999 NSW BKN020 OVC030 QNH2998INS
The pertinent part of the DCA forecast (the line starting "FM040900", meaning "From 09Z on the 4th") predicts winds from the north at 13 knots gusting to 20, four miles visibility in light drizzly rain and mist and an 800 foot overcast, continuing through 14Z.

The Andrews forecast predicts conditions becoming, between 12Z and 13Z, wind of 12 knots from the north, good visibility with "no significant weather" (NSW) and a broken ceiling at 2,000 feet, overcast above at 3,000. This is one where I hope the Zoomies have it right!

In either case, the forecast conditions are good enough to depart. How about the arrival a couple of hours later?

KBDR 031720Z 0318/0418 04014G20KT P6SM SCT040 
     FM031900 04014G22KT P6SM BKN035 BKN100 
     FM040500 05020G25KT 6SM -RA SCT012 OVC020 
     FM041300 05020G26KT 5SM -RA OVC012

The Bridgeport TAF predicts northeast wind of 20 knots gusting to 26, with five miles visibility in light rain, overcast at 1,200 feet, from 13Z. That's a sporty wind but it's nicely aligned with Runway 6. The ILS approach will be on offer and the high ceiling ought to make for a straightforward arrival.

With rain forecast at both ends of the flight there's a good chance of getting wet en route. It's October now, so the vital question becomes, "Where will the freezing level be?"

The image at left is clipped from the ADDS - Winds/Temps page. It shows where the isotherms (especially the zero degree curve) will be at 12Z tomorrow. This one is for the 725 millibar level - about 9,000 feet. If I file for 7,000 feet I'll be comfortably below the freezing level all the way along my route.

One other item to note. The nice folks at FltPlan.Com are telling me to expect an average tailwind component of +2 knots at 7,000 feet but an average headwind component of -17 knots at 5,000 feet. That is a lot of wind shear! The predicted time for the flight is 2:02 at 7,000 and 2:20 at 5,000. Of course it isn't that simple.

Potomac Approach will want me at 7,000 feet above the KBWI arrivals and New York Approach will, for their own mysterious reasons, want me at 5,000 feet over the top of KJFK. So, I'll file for 7,000 (secure in the knowledge that the temperature will be warm enough to keep water in the liquid phase) and try to convince ATC to let me stay up there as long as possible to avoid the headwind at 5,000.