MET 5506C-Synoptic Meteorology-Final ProjectMET 5506C-Synoptic Meteorology-Final Project The Ohio Valley Pre-Christmas Snow Storm of 2004The Ohio Valley Pre-Christmas Snow Storm of 2004

(Figure 2) Track of the secondary low pressure center that originated out of South

Texas, and the snow accumulation totals. (Courtesy National Weather Service)

Timeline Of Synoptic Scale Development

Dec. 21Dec. 21stst 12z 12z

Dec. 22Dec. 22ndnd 00z 00z

Dec. 22Dec. 22ndnd 12z 12z

Dec. 23Dec. 23rdrd 00z 00z

Dec. 23Dec. 23rdrd 12z 12z

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.

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.

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.

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.

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.

(Figure 1) Starting and ending times of the precipitation associated with the storm (Courtesy Midwestern Regional Climate Center)

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.

(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)

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.

Key Synoptic Features In Development and Movement of the Phase Two Cyclone

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.

What Made the Snowstorm So Unusual?

(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)

(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)

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)

So what did So what did the storm the storm

actually cost?actually cost?