[wxqc] dew points (crash with onset of Santa Anna katabatic winds)

[Dave Helms]

Hey Leroy,

Not to worry, just a case of the Santa Anna's (another example of 
katabatic "downslope" winds) blowing in from the east!
http://www.findu.com/cgi-bin/wxpage.cgi?call=CW4803&last=240

On your station's time series, you can see the winds shifting around 
from the southwest before February 5th to from the east more recently 
which also was accompanied by plunging dew point from the 40's to the 
20's at the same time while your high temperatures jumped above 80F.  
The dry air produced by the Santa Anna winds moves in from east to west 
with the coast last to see the dry air. Since the moisture distribution 
is not symmetric, the analysis is not an ideal way of determining if 
your station is producing accurate humidity measurements.   I advise you 
to ignore the short term dew point/humidity analysis flags for now until 
the Santa Anna conditions abate.

Note that the Santa Anna winds are causing the NWS to issue "Red Flag" 
warnings:
http://fire.boi.noaa.gov/FIREWX/LAXFWFSGX.html
http://fire.boi.noaa.gov/FIREWX/LAXRFWSGX.html
***A Fire Flag warning implies that conditions for wildfires are 
optimal, e.g. low humidities, high winds, and/or "dry" lightning.

More info on Santa Anna Winds:
http://www.cnn.com/2006/US/02/06/wildfires.ap/?eref=yahoo
http://www.atmos.ucla.edu/~fovell/ASother/mm5/SantaAna/winds.html
http://en.wikipedia.org/wiki/Santa_Ana_wind
http://meteora.ucsd.edu/cap/santa_ana.html

Its important to note that your CWOP observations are used at the 
National Interagency Fire Center through the MesoWest ROMAN system to 
help anticipate wildfire behavior.


Hope this helps,

Dave
CW0351

LeRoy Lambert wrote:

> */My station CW4803 red X on the dew point for the 3 day analysis 
> period.   Every station with in 15 miles has the same problem.  
> Stations KCNO, CW3917, KNOT, AD6NH, CW1226, and CW4333.  What's up 
> with that?/*
> *//* 
> */LeRoy/*
>
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