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Posted by Ray
on 5/23/2008, 9:14 am
74.74.189.214
The good news: the models agree completely that Saturday and Sunday are going to be lovely for all outdoor activities. The bad news: by 84 hours into the future, both of the two most relied-upon models (GFS and NAM), while still showing roughly similar geostrophic flow (balance between pressure gradient and Coriolis force) pattens at levels up to 500 mb (the so-called "level of nondivergence", very important...more later), go nuts as per vertical velocity fields (which determine precip). If the horizontal component of the prognosticated wind field is off by, say, 10%, so what?, for example, 3.3 plus or minus 0.33 meters/sec, the 33 cm/sec discrepancy is no big deal. But the vertical velocity fields (AKA synoptic scale ascent or decent) are critical as per precip. If the prog says minus 20 cm/sec, and what happens is plus 2 cm/sec, that 22 cm/sec discrepancy is the difference between clear skies and rain. For details as to why the models differ, the interested reader (Rick) is invited to study the Buffalo NWS Area Forecast Discussion. So, the two questions for us are:
(1) Will Saturday or Sunday be the better soaring day? Answer: although both will feature good thermals (consult your favorite Blip maps or tea leaves), if anyone's planning a substantive XC, Saturday is your ticket, because later in the day on Sunday, both NAM and GFS show us on the "back side" of the surface high, which means warm advection aloft, which means you might not get back home (why?).
(2) Will it rain on Monday? Probably. When? Who the hell knows? Stay tuned.
Bottom line: PERFECT weekend for glider gurus. We can play on Sat and Sun, then get the needed Brownie points on Monday with the family barbeque, visiting relatives, mowing lawns, satisfying the wife (if that's possible), garden prep, and so ad infinitum.
Ray
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