Status:Finalised Material from: Ervin, Linus, Tim, Fernando

 

Discussed in the following Daily reports:

 

1. Impact

 

 

 On 22-24 January a severe blizzard hit the U.S east-coast and broke records in accumulated snowfall in several places. The amount was only mm from the record in Central Park (NYC) and broke the record on JFK. For Washington DC (Dulles) it ranks as the 2nd worst snowstorm. After the cyclone New Jersey was hit by coastal flooding. 

 

 

https://www.washingtonpost.com/news/capital-weather-gang/wp/2016/01/24/snowzilla-makes-history-from-northern-virginia-to-new-york/

2. Description of the event

A nice summary of the meteorological conditions during the storm can be found here: https://www.washingtonpost.com/news/capital-weather-gang/wp/2016/01/25/the-12-best-meteorological-images-of-the-blizzard-of-2016/

The plots below show the 24-hour accumulated precipitation for 22 Jan 12z-23 Jan 12z (left) and 23 Jan 12z - 24 Jan 12z. Note the local differences around Washington DC and NYC. 


(http://www.ogimet.com)

Next plot is a preliminary plot, from the US, for the greater NYC area, showing post event snow depths in inches. For reference Long Island, east of the city, is the island in the lower right.

 



The next series of plots show the evolution of the snow depth in our analysis together with received observations.


The plots below show the evolution of the jet stream and MSLP from 19 to 24 January.



The development of the cyclone seems to be connected to a wave train triggered by a baroclinic wave six days before in the western North Pacific as we can seen from the Hovemoeller diagram for Z500 anomalies.



The plot below shows the projection of the flow on Kelvin wave mode on 19 January 00z at 150 hPa, with a strong westerly phase over Eastern Pacific, which might or might not be connected to the development of the cyclone. (from http://meteo.fmf.uni-lj.si/MODES/ )



 

3. Predictability

3.1 Data assimilation

 

3.2 HRES

The plots below show HRES forecasts of accumulated precipitation 23 Jan 00z - 24 Jan 00z (shade) and MSLP on 23 Jan 12z. The observed precipitation is in the first panel.



The plots below show the snow cover in the analysis (first plot) 24 Jan 06z and forecasts valid at the same time.




3.3 ENS

The plots below show the accumulation precipitation 22 Jan 12z-24 Jan 12z (48h) for ENS o-suite (blue) and HRES o-suite (red). The left plot is for Washington DC (obs 27-57 mm) and the right for New York City (obs 17-47 mm).


The plots below show the EFI and SOT for 72-hour precipitation 22-25 Jan all all 00z forecasts.



3.4 Monthly forecasts


3.5 Comparison with other centres


4. Experience from general performance/other cases

201401 - Snowstorm - North-eastern U.S.

201402 - Snowstorm - US east-coast

201501 - Snowfall - US east coast

 

5. Good and bad aspects of the forecasts for the event

  • Early signal (from Sunday 17 Jan 00z) and very consistent forecasts
  • Too low accumulation over NYC
  • Question about snow density for the case


6. Additional material

1 Comment

  1. Erik Andersson

    Thanks for the detailed reporting on this important severe weather case for our forecast users. I can forsee that we will becoming back to this case in future, and also that we will be reporting on our performance for this case to our committees and Council.

    Would be good to include some feedback from US forecasters on the ECMWF forecast guidance, if/when available.