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20010503: GMT

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  • Subject: 20010503: GMT
  • Date: Thu, 03 May 2001 21:57:02 -0600
>From: address@hidden
>Organization: UCAR/Unidata
>Keywords: 200105040030.f440Uhp07189

>
>Hi Steve, 
>       Things here have bee running really smoothly...thanks!  One thing
>I'm wondering about is the observation times.  I'm noticing that a lot 
>of the instability (high CAPE values, etc) is occuring at the midnight or 
>very early morning times...when I'd expect to see this in the afternoon. So, 
>if I'm looking at a Texas station, the midnight value is really around
>6pm local time? 
>
>Diana
>

Diana,
yes, weather measurements take place using Greenwich time (aka Universal time,
or Zulu time).  If you consider a weather map of the entire US, where different
states are in different time zones- using a common time coordinate is very
important.

0Z (eg midnight in Greenwich England) is 8PM EDT (7PM EST), and 12Z is
morning 8AM EDT (7AM EST)  (5AM/PM PDT, 4AM/PM PST).
So, you should be seeing higher CAPE values at the 0Z time which is generally
late afternoon in the summer. Note that this means that soundings
in the EAST are at a different relation to local solar noon/sunset than
those out west- so there will be a little statistical bias in time
correlation with longitude- in particular at the lower levels of the
atmosphere. The upper levels of the atmosphere are slower to react to
surface heating/cooling.

So, we should be talking the same, 0Z sounding in Texas is
6PM central daylight time (5PM central standard time). 

Steve Chiswell