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Posted by Ray
on 8/29/2008, 2:46 pm, in reply to "Speaking of New Orleans"
72.230.154.40
Hurricanes are like King Kong. They go wherever the hell they want to.
--Previous Message--
: Does a Hurricane go up or come down? Being a
: super low pressure system, I'd assuem it
: would go up. We need short wing gliders for
: this.
:
:
: --Previous Message--
: For the many: A lovely three-day weekend
: weather wise for all outdoor activities.
: Only one forecasting challenge for FLSC:
: when will the remnants of the front coming
: through Friday night exit Dansville
: sufficiently for blue sky to appear?
: For the few: Synopticians are fond of saying
: "What happens at the surface is a
: reflection of what happens aloft".
: Here, "surface" means essentially
: the planetary boundary layer or PBL (where
: we normally thermal), and "aloft"
: means part of the troposphere above that,
: including the "level of
: non-divergence" (at ~ 500 mb at this
: latitude), and particularly the jet stream
: higher up. We are interested in making money
: giving rides, and people are more likely to
: come out when it's sunny, even if partly.
: To have blue skies (albeit with embedded
: cumuli) requires synoptic-scale subsidence
: above the PBL, and as previously mentioned
: the magnitude of that subsidence need only
: be a few centimeters per second. Or
: conversely, a few cm/sec of ascent above the
: PBL means over-development and overcast. Of
: the 28 available plots for the Eta (= NAM)
: model, probably the most useful in this
: context is "925/850 Mixing Ratio +
: 700/500 Vert motion". The current 48 hr
: prog, valid (?) for 1200 EDT Saturday, shows
: minus 2 to minus 5 cm/sec over western NY at
: both 700 and 500 mb. Also, the mixing ratio
: maps on the same panel show relatively dry
: air over us at both levels. So that's good.
: But a couple of more items one should check.
: First, the 500 mb NAM and GFS vorticity
: maps. They both display the small feature
: swinging through today causing the dreary
: conditions right now (4 PM Thursday). For
: Saturday, they both have us free of any big
: vort maxima; however the GFS (but not the
: NAM) has a small vort max passing rapidly
: through during the day. Second, it's good
: to study the 700 mb winds, scrutinizing them
: for any short-wave mini troughs: the NAM has
: a small one which has passed to our east by
: 1200 Sat, whereas the GFS has one right over
: us at the same time. So, the model output
: is a bit contradictory: mixing ratio and
: vertical velocity being favorable, and the
: GFS 700 mb flow and 500 mb vorticity data,
: very slightly unfavorable for early
: clearing. All things considered, I'll stick
: my neck out and give a 50% chance of seeing
: at least some blue patches over Dansville by
: 10 AM , and a 90% chance of mostly sunny
: with embedded cumuli by the afternoon. But
: then, I try to be an optimist.
:
: PS I'm glad I don't live in New Orleans!
:
:
:
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