Thursday, October 15, 2009

Railroad Weather

It looks like tomorrow night will have a clear case of AmTrak Weather. The combination of moisture and freezing temperatures aloft seem to be dictating a trip to DC at 0 feet AGL.

First, take a look at where the freezing level is going to be:

The map above shows the forecast freezing levels (NAM model, 12Z run) for about the time I'd be wanting to land at VKX. You can see that my normal routing over southeastern New York and down over central New Jersey and eastern Pennsylvania, at 6,000 to 8,000 feet MSL, would have a high icing potential.

Even if I could talk ATC into a routing over JFK and down the New Jersey coast, the northern part of the route would be a problem.

Now add in the moisture. Here's the forecast simulated radar image for the same time period:

That suggests some pretty solid precip returns over the southern parts of the trip. Not a pretty picture.

Finally, let's look at a couple of Terminal Area Forecasts going out to 00Z tomorrow night:

KJFK 151737Z 1518/1624 05016G22KT 4SM -RA BKN015 OVC025
    FM152000 05017G23KT 4SM -RA BR SCT009 OVC012
    TEMPO 1521/1524 2SM RA BR OVC009
    FM160000 04020G27KT 2SM -RA BR OVC008
    TEMPO 1604/1608 4SM -RA BR OVC010
    FM160800 02020G28KT 4SM -RA BR OVC012
    FM161300 02017G25KT 4SM -RA BR OVC012

KBWI 151725Z 1518/1624 07012KT 2SM -RA BR BKN008 OVC012
    FM151900 04012G20KT 4SM -RADZ BR SCT004 OVC008
    FM152300 03013G23KT 5SM -RADZ BR FEW002 BKN004 OVC009
    FM160400 02010G18KT 6SM -RA BR OVC003
    FM161300 01010KT 5SM -DZ SCT003 OVC006

KIAD 151725Z 1518/1624 06007KT 3SM -RA BR SCT005 BKN009 OVC015
    FM152100 03010KT 4SM -RADZ BR FEW002 BKN004 OVC009
    FM160200 01007KT 5SM -DZ BR OVC002
    FM161200 36006KT 4SM -DZ BR SCT002 OVC005

In the New York City area at the probable time of departure (say, 21Z), it's looking like gusty winds from the NNE with light rain and mist and a 1200 foot overcast. And for the ETA timeframe (about 23Z to 00Z) Baltimore is forecast to have 5 miles visibility in light drizzle with a 600 foot overcast and Dulles looks to have the same weather with a 500 foot overcast.

The only instrument approach into VKX, the RNAV 6, has a Minimum Descent Altitude of 680 feet MSL, so even if I could contrive to make the flight without icing up N631S, there is an excellent chance I'd have to go missed approach at VKX and wind up at Manassas.

I shall look at the weather again in the morning, but as of now it looks to add up to a nice train trip and a late (but safe) arrival at home.

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