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(meteorobs) Resources for precise cloud prediction



>-----Original Message-----
>From: newtonj@ttc.com <newtonj@ttc.com>
>To: meteorobs@latrade.com <meteorobs@latrade.com>
>Date: Monday, November 15, 1999 4:08 PM
>Subject: (meteorobs) Clear skies????????
>
>
>
>>Local forecasts are very general, partly sunny.... mostly sunny.... partly
>>cloudy.... Where's our "resident meteorologist"? Any suggestions or info
>>would be appreciated.
>>
>>Clear skies.... Pleeeeaaaase!!!
>>
>>John N
>
>
Well, I'm not a meteorologist but in addition to being a very casual meteor
observer (I only come out of the woodwork for the major stuff :-) I am a bit
of an amateur weather watcher with a particular interest in things like
hurricanes and severe weather.

As you've noticed, the NWS and your local TV station don't make a very big
deal of PRECISE cloudcover forecasts because the vast majority of people
don't care.   We, obviously, do. Particularly for Nov. 17/18. :-)

You need to do it yourself.  Try these sites:

AVN model:  http://www.arl.noaa.gov/ready-bin/arlplot1.pl?metdata=AVN+191+km

ETA model:  http://www.arl.noaa.gov/ready-bin/arlplot1.pl?metdata=Eta+40+km

These are the two primary medium range US weather models.  The AVN is run 4
times a day and forecasts out to 72 hours, and has maps generated for 6 hour
increments.  However, it takes about 5-6 hours to run, so one should look
for the 0Z run of it beginning at about 5 to 6Z (barring computer failures
which are fairly often :-).  The ETA is currently run 2 times a day (used to
be 4, but there was a major fire in a NCEP computer several months ago which
has caused major model disruption.)  It only forecasts out 48 hours, but it
has 3 hour increments, has a  much higher "resolution" and is a bit more
advanced than the AVN. It comes out a tad earlier than the AVN usually.

Basically, on each of the pages above, you first type in your lat/long
(doesn't have to be exact, just get it roughly near where you live (North
America  only for these maps, though), and then put in a radius.....5 to 10
degrees is good.

Then you'll want to plot "Total Cloud Cover (SFC) below, make sure level is
at "SFC"  "Color Filled" seems to  work best for "Contour Type."

Then you choose the time you care about....at the bottom. It then generates
a map showing the predicted cloud cover in %.

This is a more precise forecast than you'll get anywhere else. Take it with
a massive boulder of salt, of course...computer models are often wrong, and
especially the precise boundaries of cloud cover are difficult to predict.
It gets more accurate the closer and closer you get to the event, but, on
the day of the shower, really, you're better off simply looking at real-time
satellite loops of cloud motion.

However, if you need to plan a long drive a day ahead of the Leonids, the
above forecast sites will be invaluable. It will give you a sense of where
you are hopelessly doomed in terms of cloud cover and how far you'll need to
drive and in what direction to at least have a chance.

For example, looking at the AVN (the night of Nov. 17/18 isn't close enough
to be covered by the ETA yet) for Nov. 18 at 6Z (2AM where I am, in
Maryland) it shows a clear spot over the Mid-Atlantic, with New York and New
England basically screwed (much the same as last year.)

I strongly suggest you guys come on down  :-)

John Krempasky


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