MET 5506C-Synoptic Meteorology-Final Project
The Ohio Valley Pre-Christmas Snow Storm of 2004
Synopsis: Between December 21st and 24th, a series of events transpired that are now collectively referred
to as the Pre-Christmas Storm of 2004. The effected area was the Midwest, and specifically the Ohio Valley.
The storm came in two phases. Phase one was the less severe, and resulted as a cold front associated
with a surface cyclone north of the Great Lakes encountered warmer, very moist air over the Ohio valley.
Phase two of the storm was the result of a gulf low that tracked north from the Texas/Louisiana area north
past Mississippi, Alabama and Tennessee. The storm system was followed by an arctic high pressure
system that in the days following the storm brought record cold to the very same region.
Timeline Of Synoptic Scale Development
The only significant surface feature is an 999mb low pressure
center over the Northern Great Lakes, with an associated arctic
cold front. Warm moist, gulf air is in place over the Midwest,
contrasted by artic air over Kansas and the Dakotas. Significant
upper level features include a 500mb with a negatively tilted
axis that is co-located with the surface cyclone, and a 127kt. jet
streak just south of the Great
Lakes with a core directed to the east/northeast.
(Figure 1) Starting and ending times of the precipitation associated with the
storm (Courtesy Midwestern Regional Climate Center)
Cold air is still pouring into the Midwest from Canada. The
500mb trough to the West has significantly deepened, is
positively tilted, and extends to the southwest. A weak
surface low (~1005mb) has formed over the southern tip of
Texas. A 116 Kt. Jet streak is located over southwestern
Texas, and a local anomaly of positive vorticity is located over
northern Texas and Oklahoma. The mixed precipitation for
most of the Midwest takes about a 6 hour break before the
second phase of Precipitation.
Dec. 21st 12z
Surface cyclone is now following the upper level flow up through
Mississippi, Tennessee, and the western Ohio Valley. The Jet
Core is aligned in a N/S direction as opposed to a Zonal
direction. The surface low pressure center has deepened to
~1002mb due to its interaction with the upper level vorticity
maximum. As this system tracks to the North past the Ohio
Valley, it delivers significant snow, sleet, and ice to the region.
On the back side of this system, an arctic high pressure system
builds into the area, bringing record cold temperatures with it.
(Figure 2) Track of the secondary low pressure center that originated out of South
Texas, and the snow accumulation totals. (Courtesy National Weather Service)
Dec. 23rd 12z
Dec. 22nd 12z
Dec. 22nd 00z
Dec. 23rd 00z
The 500mb trough has dug even farther into Texas, the Vorticity
Anomaly has moved to the east to Eastern Texas and Oklahoma,
and the 300mb, 115 Kt. jet core is located over the
Texas/Louisiana border. The surface low has not strengthened
much, but is now located over SE Louisiana. The surface
cyclone has now aligned itself with the jet core just to the west,
and the 500mb max of vorticity just to the W/NW, The axis of
cyclonic flow is titled steeply west, which begins to deepen the
surface cyclone.
The arctic front has swept southward, and interacted with a weak
surface front stretching from north Texas to the Ohio river in
Western Kentucky. An 850mb trough extending down from the
great lakes is active in pumping low level moisture into the Ohio
Valley. The previous 500mb trough is lifting as the Northern
cyclone has occluded, but a new, much stronger trough is
digging to the West. Mixed precipitation begins falling in the SW
Ohio Valley due to the moist flow interacting with the cold air.
(Figure 4) (Left) A plot of overnight
temperatures for the region two
nights after the storm.
(Dec 25th, 00Z)
(Figure 5) (Below) A composite
radar image from the overnight
period of the storm
(Dec 23rd, 06z)
(Both Courtesy NWS Louisville, KY)
What Made the Snowstorm So Unusual?
(Figure 3) Analysis Maps,
(clockwise from left) MSLP
overlaid with 300mb isotach
contours, 500mb heights,
and 500mb absolute vorticity.
(Dec. 23, 00z)
(courtesy Plymouth State Univerisity
online weather data center)
Key Synoptic Features In Development and Movement of the Phase Two Cyclone
An expansive 500mb trough covering with a slight positive tilt
An 850mb trough that roughly corresponds to the 500mb trough,
which serves to pump moist from the gulf to the Ohio Valley
An incipient gulf low over eastern Louisiana
- This type of low is the traditional beginning of major
winter storms in the eastern US.
A jet stream that has a N/S orientation rather than the normal
zonal direction, with multiple associated jet streaks, one of which is
centered over the Texas/Louisiana Border.
- This jet streak will not only be associated with the
amplification of the surface low but will also serve to steer
the surface low to a more northern course.
A positive anomaly of vorticity at 500mb centered over Northern
Texas and Oklahoma.
- when viewing the relative position of this vorticity max with
respect to the surface cyclone, the axis of cyclonic flow
tilts to the west with height, which by Q-G theory tells us
that there will be ascent over the surface cyclone, and
therefore the cyclone will deepen over time.
It brought large amounts of snow to areas that generally do not receive extreme amounts due to the
ample supply of moisture provided at low levels by the 850mb flow.
Its track progressed nearly due north, due to the very strong upper level jet stream—with zonal flow in,
this system would have likely proceeded up the eastern seaboard to become a traditional “Noreaster”
“training” of snowstorms resulted in many affected areas receiving up to 33 hours of nearly constant
precipitation. This resulted a somewhat narrow path of deep accumulations considering its immense size.
A very tight height gradient at upper levels resulted in a very fine line between different types of
precipitation. At many locations, layers of snow, then sleet, then rain, then snow again piled up on top of
each other. To the southeast of the storm conditions were very favorable for freezing rain.
The distance between areas of all-rain from the system and areas of all-snow from the system is narrow as
a consequence of the fact that the storm’s path aligned itself with the critical thickness rain/snow line.
There were many reported cases of thunder-sleet or thunder-snow, and these “cells” resulted in dramatic
accumulations in a short period of time.
(Figure 6) A sounding from Wilmington, OH, clearly showing the possibility
for freezing rain with the presence of a low level temperature inversion due
to evaporative cooling near the surface. (Dec 23rd, 12z)
(Courtesy Plymouth State University Online Weather Data Center)
So what did
the storm
actually cost?
17 lives (11 auto accidents, 5 heart attacks, 1 electrocution)
• Insured property losses: $230 million, Total: $900 million
• National guard used Humvees and helicopters to rescue stranded
motorists on I-64, which was not cleared till the 28th
• Over 1million homes without power at peak,
• $48,000 homes without power 2 days out,
• Estimated cost of snow removal in 4 states: $108 million
• Stores reported lost Christmas shopping sales at nearly 80%
• Airline losses estimated at $270 million
• 40% of nationwide flights on Dec. 23 delayed at least 1 hour.
• Nashville, TN: 122 auto accidents in 45 min.
• Total cost to Railroads from delays to broken rails: $7million
(Data Courtesy Midwestern Regional Climate Center)