A Review of the March 28, 2007 Tornado Event

Teresa Keck NWS North Platte, Nebraska

Courtesy of Mike Hollingshead

Introduction

March 28, 2007 in review Forecasts leading up to event Vorticity Generation Parameter (VGP)

emphasis in the warning process VGP application for future events

In Review

Progression of Day 1 Outlook

Day 1 Tornado Outlook

Highlights Dryline retrograded west by early afternoon shifting

focus westward. The VGP forecast and analysis graphics helped

refocus the forecast team to the potential for tornadoes in a storm environment where radar signatures were not clear cut.

Storms moved from 34 to 52 knots while moving through the eastern panhandle and slowed to around 26 knots as storms intensified prior to tornado development.

The 0.5 degree elevation slice was over 10 KFT off the ground.

Twelve tornadoes occurred in a 2 hour and 8 minute period. The largest tornado was rated an EF 2 that tracked 17 miles across Perkins county.

NAM 500MB Height & Wind Speed

Surface Analysis 29/0000Z

Visible Image

NAM12 CAPE and CIN 29/0000Z

LAPS CAPE and CIN 28/2300Z

LAPS CAPE and CIN 29/0000Z

LAPS CAPE and CIN 29/0100Z

LAPS Compared to RUC Wind Profile

Vorticity Generation Parameter - Resource Rasmussen and Blanchard 1998 study

Box and whisker plot of VGP showing the 10th to 90th percentile

Estimates the rate of tilting and stretching of horizontal vorticity by a thunderstorm updraft Levels 0 – 3 km on average with values of 0.2 or

greater suggesting an increasing possibility of tornadic storms.

Model data and LAPS analysis

NAM12 VGP 29/0000Z

RUC VGP 28/2100Z - 29/0000Z

Composite Radar 29/0000Z

Radar Reflectivity 29/0001Z

LAPS 0-3km VGP 28/2300Z

Composite 28/2300Z

LAPS 0-3km VGP 29/0000Z

Composite 29/0000Z

LAPS 0-3km VGP 29/0100Z

Composite 29/0100Z

LAPS 0-3km VGP 29/0200Z

Composite 29/0200Z

LAPS 0-3km VGP 29/0300Z

Composite 290300Z

Future use of VGP

Review other events to look for similarities and influence of gradients

Correlations in VGP for ranges created when CAPE and wind shear environments vary (low CAPE to high shear verses high CAPE to low wind shear)

Storm types

Questions…