SATELLITE 
INTERPRETATION 
DISCUSSION
 
NOAA/NESDIS
 Regional and Mesoscale Meteorology Team
Cooperative Institute for Research in the Atmosphere (CIRA)
 Colorado State University   Fort Collins, Colorado

January 10, 2000
Analysis of the GOES Visible Imagery from the 
23 December 1999 Lake-Effect Snow Event

Figure 1

Loop 1

An Arctic air mass moved over the Great Lakes shortly before Christmas causing a significant lake-effect snow event.  Relatively warm lake surface temperatures (Figure 1) combined with strong low-level cold advection caused lake-effect snow bands to setup downwind of the all five Great Lakes. Heavy snowfall amounts for this event were localized, but as much as 4 feet downwind of Lake Ontario and almost 2 feet downwind of Lake Erie. Click here for all references to geographic locations in this discussion. 

Visible satellite imagery for 23 December (Loop 1) shows multiple bands of lake-effect snow over Lake Huron. An area of high
clouds over Lake Erie is obscuring some of the activity, however a single band can be seen at the south end of the lake early in the day, and the northeast end of the lake later in the day. Over Lake Ontario a single band can be observed intermittently and becomes better organized as the day progresses. Wave clouds (possible standing waves) are apparent in the stable air over the land in New York and Pennsylvania. Click on images to enlarge figures or to start loops

 

Figure 2

Loop 2

 
 
 

 

 An average image (Figure 2) (calculated by taking the average of the all the images in the above loop) yields even more information.  The single band is more readily apparent over Lake Ontario. Recall there were some high clouds in the loop which made it less discernible at times. The single band over western Lake Erie can be seen to blend with the enhanced cloudiness along the southern shoreline (1). The average image supports the idea that the waves over NY and PA in the loop are stationary and are therefore most likely standing waves. Over the southeast portion of Lake Huron an area of less cloudiness (2) is evident in the wake of the peninsula in eastern Michigan. North of this minimum is an enhanced single band that extends into Ontario (3). This occurs due to the longer fetch over Saginaw Bay, as well as the additional frictional convergence due to the peninsula. There is snow cover downwind of Lake Huron from recent lake-effect snows. Notice a line of enhanced cloudiness over the eastern portions of Georgian Bay (4). This enhancement occurs along a gradient in lake surface temperatures (Figure 1) where temperatures on the eastern side of the gradient are at or near freezing (perhaps frozen). It is unclear what role this lake surface temperature gradient has in the enhancement of clouds over that region. The smaller lake southeast of Georgian Bay (Lake Simcoe) is producing no enhanced cloudiness, since it is frozen over. 

The visible imagery for the next day (Loop 2) shows the snow cover downwind of the lakes. The snow cover is most easily seen on the east and southeast side of Lake Ontario as well as on the southeast side of Lakes Erie and Huron.
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Information Contact: Lewis Grasso
CIRA/RAMM WebMaster: Roger Phillips
Author: Dan Bikos
Last Updated: January 10, 2000