Update: The Chicago NWS has decided that the totals for the blizzard that affected us last week should include all of the snowfall from the event; January 31st, February 1st and 2nd. This brings the storm total to 15.1". This now makes this month's blizzard the third largest in Rockford's history:
1. 16.3 inches on January 6-7, 1918
2. 16.0 inches on March 30–31, 1926
3. 15.1 inches on Jan 31-Feb 2, 2011
4. 15.0 inches on March 21–22, 1932
5. 13.8 inches on March 1–2, 1948
6. 12.9 inches on December 11–13, 1909
7. 12.5 inches on February 10–11, 1944
8. 12.3 inches on January 11–14, 1979
9. 12.0 inches on January 17–19, 1943
10. 11.5 inches on January 14–15, 1943
2:00 pm: Trying to measure snowfall, especially in a situation like we had last week with the significant amount of wind and the little snow that fell ahead of the main event, is probably one of the most difficult tasks for a meteorologist or weather observer. There was much talk among the meteorologists at the Chicago National Weather Service this past week as to how exactly this storm was to be measured.
The storm system itself was very complex as there were many different components to it during the 2 day event. Initially there was a lead shortwave out ahead of the storm that produced a little snow during the very early morning hours of the 1st followed by lake effect snow that made it as far west as Rockford later that morning; see post from the morning of the 1st. These totals were included, at first, with the overall snow totals giving us our 14.3"; 10.9" on the 1st and 3.4" on the 2nd. However, the meteorologists with the NWS felt that because the lead shortwave and lake effect were not the 'main system" those totals should not have been included. This was determined after taking a detailed look at numerous surface observations, radar data and synoptic weather patterns which some argued showed a brief break where no snow was falling. They felt that the correct storm total for the blizzard should have been 14.0", taking away three tenths of an inch that had fallen prior.
During the conference call with the NWS, fellow meteorologists in Rockford, Chicago and several weather observers, there was much debate as to why we would now, a week later, decide to make these changes. The official data that is sent to the NCDC (National Climatic Data Center) is based upon calendar days and not on co-op times; 7am through 7am the following day. Everything that the NWS office keeps is considered unofficial or preliminary. The purpose of making these changes not only to totals here in Rockford but also for Chicago and the Romeoville office, was pretty much for their own record keeping. They feel the purpose of the numbers can be used as a comparison and perspective to future storms.
The argument that came up during the call was that when we forecast, we forecast for the main event and not the different parts of the storm. In my opinion, the lead wave out ahead of the main low and the lake effect snow were all connected and an actual part of the storm system; even though the bulk of the heaviest snow didn't fall until mid-afternoon/evening on Tuesday and this should be included in your storm total. As a result, the NWS will NOT be changing the total to 14.0" for the blizzard event. If anything the total may go up to include the January 31st amount. If this does happen, we will update right here! Just as Jim Allsopp (NWS) put it at the end - "There has not been a snowstorm like this with all the wind, lightning and snow".
What are your thoughts on this?
No comments:
Post a Comment