Event Summary
     National Weather Service, Raleigh NC

January 13-14, 2005 Severe Weather Event


Event Headlines -
...An intense cold front marking the leading edge of a major air mass change moved across the central and eastern U.S. producing significant precipitation and some severe weather...
...One confirmed tornado was reported in Orange County with other tornadoes in Rowan county in western North Carolina and in central and south Central Virginia...


Event Overview -
An intense cold front, associated with a strong trough at 500 MB, signaling a significant change in the weather pattern across the eastern U.S., moved across the Mid Atlantic region late Thursday and into Friday, January 14, 2005. The cold front marked the leading edge of a much colder, Canadian air mass that was moving into an unusually warm and moist air mass that had persisted across the eastern U.S. for over a week.

The showers and thunderstorms associated with the cold front produced some severe weather as the front moved across the Mississippi Valley on January 12, 2005. The cold front along with some severe weather moved into the Southeast U.S. on January 13 and January 14, 2005.

Severe Weather Reports -






Severe Weather Potential

A band of showers with a few embedded thunderstorms crossed central North Carolina during the early morning hours on Friday, January 14th. The thunderstorms had a history of producing severe weather (largely damaging winds) as they moved across the Mississippi and Ohio Valleys.

In advance of these severe weather producing storms, the pre-storm environment characterizing much of central North Carolina indicated the potential for additional severe weather. A deep southerly flow into North Carolina was originating from the Gulf of Mexico, transporting considerable moisture into the area. Indeed, the precipitable water values were around 1.33 inches, well above normal for the time of year.

The 00Z January 14, Greensboro (GSO) sounding depicted a strong southerly flow. In particular, note the strong speed shear (rate of change in wind speed with height) in the low level winds. The winds quickly increased from 15 knots at ground level, averaging around 50 knots through a deep 10,000 foot layer. There is also some turning of the wind (helicity) seen as southerly surface winds quickly became southwesterly. The presence of strong speed shear near the surface and through a deep layer indicated a high potential for wind damage from convective storms. Since there was also some turning (spin) to the low level winds, the potential for tornadoes also needed to be closely followed.

The 00Z January 14 GSO sounding revealed additional clues regarding the potential for severe storms. The change in temperature with height (lapse rate) is relatively small from near the surface through a deep layer.. The relatively small lapse rate limited the air mass's instability and thunderstorm intensity; however some passing showers did precede the stronger main convective line and might have resulted in a little more instability via cooling of the temperatures in the previously unsaturated layers and hence a stronger lapse rate (change in temperature with height).

The above pre-storm characteristics, especially the very strong winds just off the surface, prompted the National Weather Service radar operators to closely monitor those convective storms featuring any type of bowing or shearing pattern as indicated by radar signatures. Such signatures are indicative of strong winds. Most of the severe storm warnings were either based on bowing segments or convective elements where gate-to-gate shear (large changes in wind speed and direction over a short distance) appeared more significant than in other parts of the line of convection. Only a few thunderstorms exhibited rotation indicative of mesocyclones. A tornado may develop from a mesocyclone's rotation and extend below cloud to the ground. Fortunately, the mesocyclones found in this severe event were short-lived and relatively shallow with depths ranging from between 7,000 to 12,000 feet. The storms appeared to intensity as they approached the northeast Piedmont counties where there was a little more turning (helicity) of the low level wind while the air mass remained just marginally unstable (lifted indices ranging from 2 to -1).




Orange County Tornado

An F0 tornado with winds up to 70 mph wind developed at around 445 AM on Friday, January 14, 2005 in Orange County, just northeast of Hillsborough. The tornado affected a small area along Saint Marys Road. The tornado had a path length of approximately a quarter mile and an estimated width of 50 yards. Winds with the tornado were likely around 70 mph.

Primarily affected were two properties along the north side of Saint Marys Road. Much of the damage was straight line in nature, including severe winds that blew open the front door of a home and then blew much of the east wall completely out of the home. On an adjacent property, a metal shed was destroyed with some of the debris carried into nearby trees to a height of over 20 feet. However, there was damage consistent with rotation along the line of storms, including tree damage facing due south, and a small outbuilding that was pushed a short distance due south off of its foundation.

Eyewitness reports indicated the tornado occurred at around 445 AM, and when the storm struck, there were sounds like a train. Small hail also was thought to have immediately preceded the storm. There were no injuries.



Preliminary tornado track - click to enlarge.





Surface Analysis

Surface Analysis from 12Z (700 AM) Friday January 14, 2005 shows the strong cold front located over central North Carolina.

A Java Loop of Surface Analysis imagery from 00Z (700 PM) Friday January 14, 2005 through 00Z (700 PM) Saturday January 15, 2005 shows the strong cold front sweeping across the Carolinas.

Surface analysis from 12Z Friday January 14, 2005






Raleigh - KRAX Radar Imagery

Raleigh, KRAX WSR-88D base reflectivity imagery from 0943Z (443 AM) on Friday January 14, 2005 is shown below. Note the line of intense thunderstorms stretching from Virginia southward to near Durham and then to near Wadesboro.

At about the 445 AM (0945Z) or just a few minutes after this radar image was taken (0943Z), a tornado touched down in Orange County, just northwest of Durham. The individual tornadic cell can be seen across northern Orange County.

A Java Loop of KRAX Radar imagery from 0002Z (702 PM) Friday January 14 through 1800Z (100 PM) Friday January 14, 2005 is available.

Raleigh, KRAX Radar imagery from 0943Z Friday January 14, 2005






Regional Radar Imagery

Regional composite reflectivity radar imagery from 11Z (600 AM) on Friday January 14, 2005 is shown below. Note the area of intense thunderstorms stretching from Virginia across North Carolina and into northeastern South Carolina.

A Java Loop of Regional Radar imagery from 18Z (100 PM) Thursday, January 13 through 12Z (700 AM) Friday January 14, 2005 is available.

Regional Radar from 11Z on Friday January 14, 2005




Radar Imagery

KRAX 4-Panel Storm Relative Velocity Imagery from 926Z (426 AM) Friday, January 14, 2005.
Weak rotation is noted within the thunderstorm cell just southwest of Hillsborough. The individual cells were moving rapidly north-northeast at about 50 MPH along the line. The cell just southwest of Hillsborough had a weak circulation that later spawned an F0 Tornado northeast of Hillsborough. The four panel image contains 8bit 0.5 degree Storm Relative Velocity (upper left), 8bit 0.9 degree Storm Relative Velocity (upper right), 8bit 1.3 degree Storm Relative Velocity (lower left), and 8bit 2.4 degree Storm Relative Velocity (lower right).

The green shades are targets moving toward the radar, which is located to the southeast (lower right of image). The red shades are targets moving away from the radar.

Click on the image to enlarge.

 - Click to enlarge


KRAX 4-Panel Storm Reflectivity Imagery from 926Z (426 AM) Friday, January 14, 2005.
A line of thunderstorms that produced scattered severe weather across central North Carolina is visible on the 4-panel imagery below. Embedded within the line are several cells with the most prominent being the cell just southwest of Hillsborough. This cell had a weak circulation with it that later spawned an F0 Tornado northeast of Hillsborough. The four panel image contains 8bit 0.5 degree Reflectivity (upper left), 8bit 0.9 degree Reflectivity (upper right), 8bit 1.3 degree Reflectivity (lower left), and 8bit 2.4 degree Reflectivity (lower right).
Click on the image to enlarge.

 - Click to enlarge






Selected Photographs of the Severe Weather Event
Photos courtesy of Darin Figurskey
(Click the image to enlarge.)

Two properties were primarily impacted by the tornado and the photos below show some of the damage to those properties. The properties are located along the north side of Saint Marys Road in Orange County, NC. Much of the damage was straight line in nature, including severe winds that blew open the front door of a home and then blew much of the east wall completely out of the home. On an adjacent property, a metal shed was destroyed with some of the debris carried into nearby trees to a height of over 20 feet. However, there was damage consistent with rotation along the line of storms, including tree damage facing due south, and a small outbuilding that was pushed a short distance due south off of its foundation.

Severe winds blew open the front door of this home and then blew much of the east wall completely out of the home  - Click to enlarge           View of a metal shed that was destroyed with some of the debris carried into nearby trees to a height of over 20 feet  - Click to enlarge           View of a metal shed that was destroyed with some of the debris carried into nearby trees to a height of over 20 feeth - Click to enlarge


View of damage to trees - Click to enlarge           View of damage to trees - Click to enlarge           View of damage to trees - Click to enlarge          




Final Thoughts

Low topped storms in convective lines characterized by strong speed shear with high winds near the surface are not atypical for cool season convective storms in central North Carolina. The challenge is to anticipate which storms with bowing convective line segments and/or small scale circulations (gate to gate shear) will result in wind damage or even a tornado. Subtle changes over small distances in the air mass characteristics and the driving meteorological features producing the storms are hard to determine. Meteorological observations are not available sufficiently to provide a storm scale analysis, leaving the radar meteorologist with little to go on beyond recent storm history and the radar signatures as they are evolving in real time.





Case Study Team

Michael Strickler
Scott Sharp
Douglas Schneider
Kermit Keeter
Darin Figurskey
Jonathan Blaes

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