Re: XC Skies and BLIPS agree with Dr. Ray
Posted by Ray on 4/11/2012, 1:31 pm, in reply to "XC Skies and BLIPS agree with Dr. Ray"
Indeed. The latest (2 PM) Area Forecast Matrices still have B2 for most of Thursday afternoon, for Warsaw, Wellsville, Geneseo, Olean, etc, whereas Cl or FW (the best) everywhere on Friday. I'd give maybe a 50/50 chance things could break up Thursday afternoon....and if they did, it would be a spectacular soaring day, with the fresh NW flow and cold advection, maybe even cloud streets. But if they don't, we are SOL. So it's a gamble. |
Friday is the sure bet.
: Looking at NAM forcasts from XC Skies and the
: BLIPS, Friday looks good going south down to
: Wellsville and Grand Canyon. Good lift
: after Noon until 5 PM. Usable lift to 6,000
: ft most of the way. Light WNW winds. Of
: course, things could change. Looking for a
: tow pilot for Friday.
: --Previous Message--
: To mount an operation people wanna know ASAP
: what's it gonna do. If Thursday is socked in
: with overcast, obviously they will opt for
: Friday. Bottom line: still too early to
: call. Why?
: Here's a critically-important concept: The
: presence of a dry adiabatic lapse rate in
: the sub-cloud layer is a necessary
: condition for robust thermal activity,
: but....not a sufficient one. Why? Because
: adiabatic means the layer has been
: well-mixed...but not necessarily that it is
: still being well-mixed! Given an initially
: dry adiabatic layer and clear skies in the
: morning, when the sun comes out thermals and
: clouds start popping. Now if each cloud that
: forms doesn't quickly dissipate, pretty soon
: the sky is overcast, the sun is blocked, the
: layer goes dead, but the lapse rate is
: still adiabatic . That happens when the
: synoptic (large) scale vertical velocity is
: zero or slightly positive...the clouds that
: form aren't forced down, where they are
: warmed and dissolve...they just sit there.
: But if the synoptic scale vertical velocity
: is even a little bit negative, they do that,
: you have partial cumulous cloud cover (or
: "equilibrium between formation and
: dissipation", in the lingo), and a
: great soaring day. But the vertical velocity
: fields, being small compared to the
: horizontal velocity fields (i.e. the wind),
: are often near the error margins of the
: models themselves. If you look at this
: morning's 36 hour prog for the VM/MR
: (500/700 vertical motion, 850/925 mixing
: ratio) panels, i.e. 12 hours fresher that
: last night's...you still see negative
: (blue), but..the very next panel set (for
: 1800 UTC) now has, at 700 mb, a little chunk
: of yellow (positive) over western NY. Wow.
: That was not there last night. What a
: difference 12 hours makes. That's why this
: morning's NWS discussion now has this:
: BY 12Z THURSDAY HEIGHTS WILL BE ON THE RISE
: AND DEEP LAYER MOISTURE PULLING AWAY...
: ENDING THE RISK OF ANY PRECIP. MAIN
: CHALLENGE THEN WILL BE CLOUD COVER AND
: TIMING OF ANY CLEARING. GIVEN THAT 850MB
: TEMPS ARE STILL DOWN AROUND -4C WITH
: NORTHWEST FLOW...SOME CONTRIBUTION OF LAKE
: MOISTURE WILL HELP ENCOURAGE CLOUD FORMATION
: IN ADDITION TO THE GENERAL LINGERING LOW
: LEVEL MOISTURE FORECAST TO SOME EXTENT BY
: BOTH THE NAM/GFS. WITH THIS IN MIND...HAVE
: CONTINUED WITH A FAIRLY PESSIMISTIC TREND
: WITH CLOUDS LINGERING THROUGH AT LEAST THE
: FIRST HALF OF THURSDAY. MAY SEE SOME
: SUNSHINE DEVELOP DURING THE
: AFTERNOON...ESPECIALLY NEAR THE LAKES AS
: THEY FLIP FROM UNSTABLE TO STABLE DURING THE
: PEAK OF AFTERNOON DIFFERENTIAL HEATING.
: Not to be deterred, 5 of the 6
: Buffalo/Rochester TV major network
: forecasters forecasted a mostly sunny
: Thursday at dawn this AM...the public loves
: good news. But one of them, cleverly,
: omitted the "5-day" panel
: sequence, you know, the one with a little
: grahpic (sun, clouds, rain or snow) on each
: one, and replaced it with a 5-day
: temperature trend. That, of course, is much
: easier to predict.
: Obviously we need a fresher set of progs.
: Will have same this afternoon, stay tuned.