2008-01-09 Lake Effect Snow at NYC - A Rare Event




  This afternoon at work I happened to look out of my office window and saw a band of clouds with snow falling from them in the distance - I grabbed a shot with my cell phone camera (Figure 1.) Since I knew there was a chance of snow showers because of a cold pool moving overhead at 500mb, I wasn't that surprised. But I decided to check the radar, and was surprised at the banded nature of the precip (Figure 2). This led me to look at a wider radar view (Figure 3), in which I discovered that the bands reached all the way back to the Great Lakes. Wow! Lake Effect snow bands had made it all the way to New York City. In my personal experience I would estimate that this happens only about once every 3 years or so in the NYC area.

  I've included the surface, 500mb and 850mb charts to show the synoptic setup. The Lake Effect precipitation was embedded in a very strong, uniform low-level 850mb flow which extended all the way from Lakes Erie and Ontario into the NYC area. I've also included a skewT from RUC to show how well the low-level was mixed and exactly where the low-level convection was located (high RH at 750-850mb).  Finally I added a nice close-up 1km resolution satellite image from that time. Note that there are also southwest-northeast oriented orographically-induced wave clouds produced by the northwesterly flow over the Appalachian mountains, giving the whole image a rare cross-hatched appearance over some locations.




Figure 1. Looking southwestward from Queens County towards the southern end of Manhattan, Note the northwest to southeast band of snow showers. The rectangular building in the lower right is the U.N. building. Courtesy Phil Lutzak.


  Figure 2. Radar reflectivity from WU at 1935 on 2009-01-09. Courtesy Weather Underground.   Figure 3. Radar reflectivity from RAP at 20Z on 2009-01-09. Courtesy RAP/UCAR.  


  Figure 4. Surface conditions at 18Z on 2009-01-09. Courtesy HPC.   Figure 5. 500mb conditions forecast by GFS for 18Z on 2009-01-09. Courtesy NCEP. Larger version.  


  Figure 6. 850mb conditions forecast by GFS for 18Z on 2009-01-09. Courtesy NCEP. Larger version.   Figure 7. SkewT from RUC for 20Z on 2009-01-09. Courtesy RUCsoundings. Larger version.  

  Figure 6. Visible satellite image at 1945Z on 2009-01-09. Courtesy NOAA satellite images.