METR 360
Lab
11
Lake Effect Snow Forecasting
Forecast
models
have become very effective on the synoptic scale, although human
forecasters
can usually improve on their accuracy.
The more difficult 21st century weather forecast
challenges occur with
smaller, mesoscale forecasts, mainly due to problems with model
resolution and
assumptions. Lake effect is a classic
example of a local forecasting problem in which a synoptic situation
can be
well understood and forecast but the scale of the weather phenomena
make
individual location forecasts problematic.
In this lab, we will study three cold season examples and in
each case, lake
effect was a significant element. After
studying the synoptic maps, data, and numerical guidance, you will be
asked to think about the lake effect component.
Case 1: Classic
set up over Lake Michigan
In
Fall 2013, the lake
effect station chosen for WxChallenge was
Grand
Rapids, MI (KGRR). Downwind from Lake
Michigan,
this city experienced light
snow overnight and during the day on December 7. Click
here for the radar loop. KGRR
is east of the lake. The 12Z surface map showed an Arctic High west of
Michigan with a pressure gradient
over the lake (click
here for loop). Other
information and observations can be found on the 850 hPa map, 500 hPa
vorticity map,
and 250 hPa map, all from 12Z on December 7. The Great Lakes water temperature map from Dec 5 is also available.
For
this lab you
must answer questions 1-7 in a text or Word file.
Start here:
1.
Based on the
observed conditions from the map links already given,
write a
discussion in the NWS format (for an example, click here). Your
discussion must describe what’s happening in enough detail so
that a
professional meteorologist will understand both the general synoptic
situation
and the nuances that pertain to lake effect.
2.
Based on the observed maps and information given for this lab, why was
the lake effect snow light with multiple small bands at KGRR, rather
than a single, very heavy band?
Case 2: Buffalo lake effect “
Snow Blast”
On
November 18,
2014, Buffalo experienced one of the most intense lake effect squalls
in
history. Images of the wall of snow
across Lake Erie are still iconic on the Internet:
"Wall of Snow" over Lake Erie
The
radar loop for this case shows a very different reaction than you
saw in
the Grand Rapids case and the observations
show a prolonged period of measureable snowfall,
As in the first case, you must become familiar with the surface map for 00Z Nov 18, surface map loop, 850 hPa map, 500 hPa vorticity map, and 250 hPa map. You also have, as before, the Great Lakes water temperatures from Nov 15.
For this Buffalo case, the resulting lake effect squalls were very different in terms of intensity as well as structure. Here are your questions:
3. How is the synoptic setup different from the Grand Rapids case? Wherever possible, be quantitative.
4. How do these conditions work to create such a different lake effect event?
5. Was the forecast guidance (MOS in an Excel spreadsheet, and 24 hour surface prog) helpful in guiding you to the correct forecast? Why or why not?
Case 3: Syracuse 2012
In the Fall of 2012, WxChallenge chose Syracuse, NY as their northeast station. Late in the day on Nov 28, radar showed what appeared to be a long single lake effect band set up on the south shore of Lake Ontario. Observations from 12Z Nov 28 to 12Z Nov 29 featured a number of hours with S- but little accumulation which may indicate that the long shoreline band was not as strong as it looked.
You again have a surface map loop for the same times as the observations and, for 00Z Nov 29, the U.S. surface analysis, 850 hPa map, 500 hPa vorticity map, and 250 hPa map. The Great Lakes water temperatures were from Nov 29. Your MOS digital forecast was from the NAM that was initialized at 00Z Nov 28, 2012 and the 24 hour surface prog was based on the same 00Z initialization.
Please answer the following:
6. Was this pure lake effect, lake-enhanced precipitation, or not lake effect at all? Or was it something other than those choices? Justify your answer using the information given.
7. Would you have made an accurate forecast for this case using this MOS guidance? Why or why not?
Send your text or Word file to Jerome.Blechman@oneonta.edu