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<DIV>Hi Stan,</DIV>
<DIV> </DIV>
<DIV>I would not be concened with hourly QC stats, you have to look at the longer term trends. I looked at your recent 24 hour QCMS graphs (AP555, WA1LOU-15):</DIV>
<DIV><A href="http://pond1.gladstonefamily.net:8080/cgi-bin/wxqchart.pl?site=AP555">http://pond1.gladstonefamily.net:8080/cgi-bin/wxqchart.pl?site=AP555</A></DIV>
<DIV> </DIV>
<DIV>1. Pressure: Your observed data seems to have a 1 mb (00.03 inch) low bias, which indicated a positive adjustment of +00.03 inch (INS) increase. Your goal should be +/- 00.03 inch of the analysis.</DIV>
<DIV>2. Temperature: In general, your temperature looks good. There could be an issue with your temps running a bit warm during maximum heating which <<could>> indication a shielding issue. Your goal should be +/- 1.0F of the analysis; but +/- 3.0F is good given the local influences that your refer to. The thing to avoid is solar comtamination of the temperature sensor.</DIV>
<DIV>3. Dew Point: Its pretty clear your dew point reports are consistently running too hot by +5 to +7F. Home weather station sensors are typically challenged in their measurements of humidity so you are not alone. I have the same problem with my Peet Bros hygristor (dew point) sensor and adjusted the values by 3F using a potentiometer/set screw located on the temp/dew point board using Peet's instructions. See the picture at the bottom of this page:</DIV>
<DIV><A href="http://mywebpages.comcast.net/dshelms/tanterra_sensors.htm">http://mywebpages.comcast.net/dshelms/tanterra_sensors.htm</A></DIV>
<DIV>If you can adjust your dew point, do it during a well mixed (moderate winds) a day or two after a cold front passage before the return flow develops and use the larger ASOS (not AWOS) dew points as a basis for comparison. The goal should be to get within +/- 2F of the analysis, but +/- 4F is reasonable.</DIV>
<DIV>The good thing about your dew points is that they are consistent and someone using the data can generally correct the bias. </DIV>
<DIV>4. Wind Direction and Speed: Very tough to assess "correctness" of winds for personal weather stations as they are usually in the suburban tree canopy and the anemometers are at various non-standard heights above ground level. Your setup seems to be better than most at measuring winds without influence of the urban canopy. Looking at the weekly and monthly QCMS data, you don't have any "flagged" events over the long term. The thing to do is watch your local ASOS stations: KHVN (New Haven), KOXC (Oxford), and KHFD (Hartford) during a moderate winds in the afternoon when there are no radiation inversions in your area. It may be the case that your wind direction is off by 20 degres (need to add +20 degrees) as compared to the environmental story, but I really can't say without watching it for a length of time during a wind event.</DIV>
<DIV> </DIV>
<DIV>The analysis field is largely based on an optimal interpolation of your neighbor's observations. See here:</DIV>
<DIV><A href="http://www-sdd.fsl.noaa.gov/MSAS/qcms_descrip.html">http://www-sdd.fsl.noaa.gov/MSAS/qcms_descrip.html</A></DIV>
<DIV> </DIV>
<DIV>Hope this helps,</DIV>
<DIV> </DIV>
<DIV>Dave</DIV>
<DIV>CW0351</DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid">-------------- Original message -------------- <BR><BR>> I have been receiving weather quality reports for the past week and I am not <BR>> sure how to interpret the information I am receiving. Here is the first line <BR>> of the latest report I received: <BR>> <BR>> * POT TEMP * DEW PNT * DD * FF <BR>> * (DEG F) * (DEG F) * (DEG) * (KNT) <BR>> * 36(-2.4)*33.6(-6.9)* 297(17.7)*10.4(-3.5) <BR>> <BR>> I assume the first number in each column is my weather station's reading and <BR>> the number in parenthesis is the observed error of the first reading. <BR>> <BR>> The explanation received with each quality report states, "The values <BR>> displayed are 'Observed (error)' The error value is 'analysis - observed'. <BR>> I.e. if your observed value is higher than the computed value, then the <BR>> error will be negative." <BR>> <BR>> Accordingly, my POT TEMP of 36 is 2.4 degrees higher than the computed <BR>> value, my DEW PNT of 33.6 is 6.9 degrees higher than the computed value, and <BR>> my FF of 10.4 is 3.5 knots higher than the computer value. Is that a correct <BR>> interpretation? <BR>> <BR>> What about the positive observed error? Is my DD of 297, 17.7 degrees LOWER <BR>> than the computed value. <BR>> <BR>> How big a computed error should one be concerned with? I imagine local <BR>> conditions play some part in causing a local reading to be out of kilter <BR>> with the computed value, but when is a local reading so far out of whack <BR>> with the computed value that it indicates that something is wrong with the <BR>> weather station equipment. My guess is that if my POT TEMP of 36 is 2.4 <BR>> degrees higher than the computed value, then that is not something to be too <BR>> concerned about, but if my DEW PNT of 33.6 is 6.9 degrees higher than the <BR>> computed value, is that something I should check out? <BR>> <BR>> And now for the one more question, how is the computed value arrived at? Is <BR>> it essentially a comparison to the other nearby weather data? <BR>> <BR>> Thank you for any help any one can provide. <BR>> <BR>> Stan Horzepa, WA1LOU <BR>> <BR>> <BR>> <BR>> <BR>> _______________________________________________ <BR>> wxqc mailing list <BR>> wxqc@lists.gladstonefamily.net <BR>> http://pond1.gladstonefamily.net:8080/mailman/listinfo/wxqc </BLOCKQUOTE></body></html>