Transcript 00 UTC Monday

10-11 January 2011 Winter Storm: Key Points
• Very cold air mass plunged far south, making conditions in
northern AL, GA, and SC conducive for snow
• Very dry air to the north over NC and VA prevented much of
the precipitation from reaching the ground until Monday
afternoon; heaviest amounts were to the south, which is
climatologically unusual
• By the time the lower troposphere was sufficiently moist, dry
air aloft was beginning to cut off dendrite formation; some
moderate snow bands still formed across SC and NC,
resulting in quick bursts of snow late Monday
• Dry air aloft and “warm” cloud tops, coupled with a moistened
lower troposphere, resulted in persistent freezing drizzle
Monday night into Tuesday morning
• Storm failed to strengthen off the Southeast coast; a likely
culprit was the system upstream over the Plains, which may
have robbed the east coast system of its energy
An unusual snowfall distribution…
00 UTC Monday
06 UTC Monday
Strongly negative AO/NAO with the polar jet
displaced far to the south
Long-wave trough to the west with short-wave
trough moving through the Deep South
12 UTC Monday
Snow is reaching the ground in GA
and SC by early Monday morning
Very dry air mass over
mid-Atlantic, VA, and
NC prevents snow from
reaching the ground
12 UTC Monday
Blue line = 0 deg isotherm
00 UTC Monday: GSO
Cold, dry column at GSO
before event begins
00 UTC Monday: BMX
Warm nose and FZRA at
Birmingham early in the event
00 UTC Monday: FFC
Narrow warm nose
and sleet at Atlanta
15 UTC Monday
1628-1748 UTC Monday
Dry air to the north eroding
the leading edge of
precipitation in central NC
18 UTC Monday
1815 UTC Monday
Dry slot moving across
the Deep South is cutting
off moisture in the
dendritic growth zone
2138 UTC Monday
“Banded” structure to the
precipitation across the
Carolinas
21 UTC Monday
Snow begins to reach
the ground in central NC
2215 UTC Monday
00 UTC Tuesday
00 UTC Tuesday
700 mb
Southwesterly flow at
700mb helps warm up
the low-levels
Dry air aloft (above 700 mb)
beginning to starve the
dendritic zone of moisture
06 UTC Tuesday
Freezing drizzle overnight
in central NC due lack of
dendrites, “warm” cloud
tops, and moist lower
troposphere
12 UTC Tuesday: GSO
Did the upstream longwave trough steal some
of this storm’s energy???
06 UTC Tuesday
1
2
1 and 2 above correspond to the soundings on the next slides
Note the dramatic subsidence
inversion and 1000-500 mb
thickness values!
1
2