September 3-4, 2012 Storm Summary for Weak Tornadoes

SEPTEMBER 3^rd - 4^th, 2012 WEAK TORNADOES

Introduction

Some remnant energy from once Hurricane Issac moved across our area during the September 3-5, 2012 time frame. In addition, this enhanced the tropical moisture across the area with surface dew points in the lower to mid 70s. The atmospheric conditions were comprised of some instability and wind shear (change in direction and speed with height). Since the instability was not exceptionally high, thunderstorms that tended to develop did not achieve tall updrafts in general. A cold front finally moved through most of our region on September 5, 2012 that knocked down the dew points some.

There were two events that occurred, which involved weak tornadoes. The weak tornadoes, EF0 with winds between 65-85 mph, are typical of what occurs in our part of the country. These are mainly spin-ups that develop and dissipate quickly. This was again the case on September 3^rd and 4^th. The thunderstorms that spawned these weak and short-lived tornadoes were in the same environment. This was characterized by deep tropical moisture and also wind shear (wind shear is a change in wind direction with height and also even speed). This creates a rolling motion in the atmosphere, and when storms develop rotation, this can then be tilted vertically by the storms updraft resulting in a tornado. Because of the tropical moisture that was in place, the local condensation level, or LCL, was rather low. The lower this is to the ground, the greater chance of a tornado occurring given other favorable parameters such as wind shear.

The focus here is with the September 4^th tornado that hit the Mount Ephraim, New Jersey (Camden County) area, as it occurred not too far from the Philadelphia Terminal Doppler Radar (TDWR, TPHL). Some brief information about the September 3^rd Camden, Delaware tornado is also listed. The velocity data also showed as the hook became more pronounced, the wind strengthened and the velocity data tightened up.

Radar Imagery

The close proximity of the Mount Ephraim tornado to the TPHL radar resulted in several impressive scans of the storm. This image shows a well-defined hook that developed.

This velocity image from the TPHL radar shows the rotation associated with the storm that produced a brief tornado in Mount Ephraim. The green color is wind blowing toward the radar and red is wind blowing away from the radar. Where this becomes aligned next to each other, indicates that the air is rotating. The tighter this is indicates where the tornado is located. In this loop, the velocity couplet tightens up and then tends to weaken.

This is a loop of the storm reflectivity from the TPHL radar of the storm that produced the weak tornado. Note the well-defined hook that developed, which then curled up on itself before weakening.

This is a loop of the velocity data from the TPHL radar. The green color is wind blowing toward the radar and red is wind blowing away from the radar. Where this becomes aligned

next to each other, indicates that the air is rotating. The tighter this is indicates where the tornado is located. In this loop, the velocity couplet tightens up and then tends to weaken.

Warnings and Storm Summary

Click here to read the Tornado Warning for Kent County Delaware on September 3^rd

Click here to read the Tornado Warning for Camden County New Jersey on September 4^th

The tornadoes typically in our area usually develop and then dissipate quickly. This was the case once again during these September 2012 events. In the case of the September 4, 2012 Mount Ephraim tornado, the funnel appeared to touch down for a brief time with the main rotation remaining disconnected from the ground. This would explain the limited damage despite the impressive look on the radar imagery.

Click here to read the Storm Survey Report for the September 3^rd Kent County Tornado

Click here to read the Storm Survey Report for the September 4^th Camden County Tornado

Storm Pictures and Damage