NorthShoreWx Posted March 29, 2017 Share Posted March 29, 2017 Ray Martin and a colleague have generously extended the ISP data record back to 1963: I've captured all of this and generated a snowfall record for ISP from 1963 through this year. It is complete from the perspective of the record that it was extracted from, but it is not complete: http://www.northshorewx.com/ClimateData/IslipDailySnowfall.pdf Prior to June 1999 and since January 2004 the record looks reasonable. It contains no snowfall for the 4 seasons from 1999 - 2000 through 2002-2003, nor for December 2003. On many dates during that period, there was daily snow depth reported, but no snowfall. I calculated the 30 year average from this data for the period 1980 - 2010 and came up with 23.5", which is a hair shy of the average for the period of 23.7" reported on the OKX climo page. I'm not sure why the slight difference, but just to check a little further I compared the greatest monthly snowfall totals shown for each month on the OKX site with the corresponding monthly totals from Ray's data and it matches exactly. My conclusion is that not withstanding the 0.2" error from an unknown source, this data is the same that was used for the OKX climo number. During the 4+ year period when no snowfall was reported at ISP, Upton (BNL) recorded 157.8" of snow and I measured 156.6" at my location. Conservatively estimating 135" at ISP during that period (about 14% less), the recalculated snow fall climo is as follows: The 1981 - 2010 average snowfall for ISP was 28.0". The average seasonal snowfall since the inception of the record (1963 - 2017) was 29.7". I've known this record was significantly off, but this is the first time I've been able to quantify how much. It might or might not be interesting to know what was different in the record keeping from late 1999 through the end of 2003. Link to comment Share on other sites More sharing options...
famartin Posted March 29, 2017 Share Posted March 29, 2017 The answer to your question (about what was different 1999-2003) is right in the METAR remarks on 8/1/1999... https://www.wunderground.com/history/airport/KISP/1999/8/1/DailyHistory.html SPECI KISP 010503Z 20010KT 8SM CLR 26/23 RMK AO2 KISP ASOS NOW COMMISSIONED $ Link to comment Share on other sites More sharing options...
NorthShoreWx Posted March 29, 2017 Author Share Posted March 29, 2017 Well now, that is interesting. Someone was still measuring snow there because ISP was frequently in the PNS back in those days. I wonder if the missing snowfall data might still exist in its entirety. When did the contract observer program at ISP start? Link to comment Share on other sites More sharing options...
famartin Posted March 29, 2017 Share Posted March 29, 2017 The issue wasn't that they weren't measuring. Its that, back then, when ASOS got commissioned, the flow of snowfall to NCDC got disrupted. Before ASOS, there were either computer files (called MAPSO, Microcomputer-Aided Paperless Surface Observations) or paper forms which were sent to NCDC, which had all the snowfall. When ASOS went operational, the observers had to enter it directly into the ASOS to get it to NCDC, and in many cases, that simply didn't happen. Only after a WFO started doing CF6 products, and then only after NCDC was informed to check the CF6 product for the snowfall, would the snowfall end up where it was supposed to be. Link to comment Share on other sites More sharing options...
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