Sunday, October 28, 2012

Mountains, Snow, and the Frankenstorm

Hurricane Sandy, a.k.a. The Frankenstorm, remains a serious threat to the eastern United States.  I'm going to leave the wind, flood, and surge discussion to others (official forecasts at and instead talk in this post about some interesting and likely influences of topography on the event.

Current forecast models have Sandy making landfall somewhere between the Delmarva Peninsula and New York City.  For example, the NAM initialized this morning (1200 UTC 28 Oct) has Sandy making landfall in central New Jersey.

1200 UTC 28 Oct 2012 initialized NAM forecast of 12-h accumulated
precipitation (inches color filled), 925 mb streamlines, and 850-mb
0ºC isotherm (red) valid 0000 UTC 30 Oct 2012.
During landfall, precipitation is heaviest over the mid-Atlantic states.  To the north, where the flow at 925 mb (roughly mid-mountain level for the higher eastern ranges) is southeasterly to northeasterly, one can clearly see the influence of the terrain on precipitation, which is heaviest over the White Mountains of New Hampshire and hills of central Massachusetts, Green Mountains of Vermont and Berkshires of Massachusetts, and Catskill Mountains of southeastern New York.  Less precipitation falls over the intervening Connecticut River and Hudson River Valleys.

The influence of these ranges continues as Sandy moves inland and the flow over the region transitions to southeasterly, with the Adirondacks also getting in on the action.

1200 UTC 28 Oct 2012 initialized NAM forecast of 12-h accumulated
precipitation (inches color filled), 925 mb streamlines, and 850-mb
0ºC isotherm (red) valid 1200 UTC 30 Oct 2012.
Note how the more inland mountain ranges (following the flow) receive less precipitaiton.  I suspect this is a reflection of airmass transformation, the drying of the airmass as precipitation falls out over upstream barriers.  One can also see some changes in the location of heaviest precipitation, which is partly related to the position of the large-scale precipitation shield, as well as changes in the direction of the flow and it's orientation relative to the terrain.

But for skiers the real interesting orographic effects happen in West Virginia.  During the period encapsulated by the images above, the mountains of West Virginia are in moist northwesterly flow and experience strong upslope.  In addition, Sandy taps into colder air that is presently in place over the midwest.  The red line in the images above shows the 0ºC isotherm at 850 mb (about 5000 ft) and you can see the tongue of cold air that wraps across West Virginia and around Sandy.

Thus, the upper-elevaitons of the mountains of West Virginia are expected to experience heavy snowfall during this period.  Check out this morning's National Weather Service forecast for Snowshoe.

Source: NWS
While Sandy could bring skier's delight to the mountains of West Virginia (at least for those willing to earn their turns), I don't wish to trivialize the storm in any way, shape, or form.  The forecast from the National Hurricane Center is quite clear:


In addition, the storm is broad in scale and will have impacts across much of the mid-Atlantic and Northeast United States.  Effects will vary, however, depending on location.  This is a complicated storm.  Stay tuned to forecasts and heed warnings if you live in areas that will be affected by the storm.


  1. Hi Jim, I knew I could come here for some great analysis of this storm. Do you have any suggestions on where to find similar analysis of the storm and all of its complex intricacies that make it so unique, aside from NOAA Discussions? Coverage on CNN and the major outlets just doesn’t cut it.
    I really appreciate your blog and all of the in-depth coverage and analysis you provide.

    1. Try Jeff Master's Wunderblog and the Capital Weather Gang. A quick google should get you to them.

    2. Echoed - thank you.