Re: Sensor tweaking and other mysteries

From: Ken Poulton (poulton@zonker.hpl.hp.com-DeleteThis)
Date: Fri Aug 20 1999 - 00:13:23 PDT 

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Date: Fri, 20 Aug 1999 00:13:23 -0700 (PDT)
From: Ken Poulton <poulton@zonker.hpl.hp.com-DeleteThis>
Message-Id: <199908200713.AAA11988@zonker.hpl.hp.com-DeleteThis>
To: wind_talk@opus.hpl.hp.com-DeleteThis
Subject: Re:  Sensor tweaking and other mysteries
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> I am perplexed. This goes beyond Call of the wind sensor correction
> coefficients. Now two airport sensors are invloved, Ken Pulton's report
> and what you get if you call SFO.
> Ken's (knot denominated) page reports:
> 99/08/19-1456 SFO 72 55 280 20 . 10 29.95 Clear
> 99/08/19-1556 SFO 70 54 260 23 . 10 29.94 Clear pk wnd 26026
> However, if you call SFO they give you 16 and 17 (compared to 20 & 23)
> at 3 and 4 p.m., respectively. How come??????

Here is the info I was once given:

    NWS and the FAA maintain separate weather operations at SFO. The
    FAA operates the 877-3585 "ATIS" recording, while NWS does the
    reports we get by network. They share the temperature and dewpt
    instruments, but for wind the NWS has one instrument near the
    intersection of the two main runway pairs, while FAA has 6
    instruments around the runways. One other important difference is
    that FAA reports magnetic directions, while NWS reports true
    directions. To convert, add 17 degrees (rounded to 20, generally)
    to the FAA (phone) report to get true readings. The terminal
    forecasts use true directions as well.

I agree that 6 knots is way higher than seems possible.

Ken Poulton
poulton@opus.hpl.hp.com-DeleteThis

Meteorology, n.: A psychology of the science of finding a pattern in the
randomness of weather behavior in order to forecast future random
weather behavior events. -- Jonathan Leffler

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