July 10, 2000 Severe Weather

Ever wonder why the National Weather Service issues tornado warnings? We look for a variety of signs on our Doppler Radar system. One of the signs we look for is a hook echo.  A hook echo is a a hook-shaped reflectivity image off of our radar. Reflectivity is a measure of the energy bounced off of a thunderstorm and sensed by our radar system.

07-10-00 Base Reflectivity Radar  

Above, you can see the reflectivity image our radar took of a hook echo between Nemo and Lead. It seemed to move along Nemo Road. Rapid City is in the lower right-hand corner of the image. If you click here or on the image, you can see a full picture of the radar image. This image was taken around 4:03 PM MDT on July 10th, 2000.

When you see reds and dark reds on a radar image, it usually means precipitation falling out of the storm is very heavy. The highest reflectivities are hail a lot of the time. Hail reflects a large amount of energy toward our radar. Look at the bottom of the page for a wall cloud picture that was taken at about the same time the radar images were seen. There are also some pictures taken by Chris Escandor from Rapid City.  He caught a few shots of the storm from the east side of Rapid City.  There is one picture that includes a "Beaver Tail."  This is the line of clouds that is extending to the right of the main rotating storm cell, just above the highway sign.

Another item that we look for is rotation within the thunderstorm. Rotation is detected using the Doppler shift. The Doppler shift is the change in frequency of a moving object as it moves toward the radar and as it moves away from the radar. Think of the last time you were at a railroad crossing and a train was passing your location. As the train came toward you, the pitch of the train whistle increased rapidly. As the train moved away from you, the pitch of the train whistle decreased at a much slower rate. This shift in frequency of what our Doppler Radar detects.

0.5 Storm Relative Motion

The image above shows what our radar detected at 4:03 PM MDT on July 10th, 2000. This is at the same time of the reflectivity image above. You can click here or on the image for a larger picture.

The red colors are showing air moving toward the left-hand side of the picture, or away from the radar. The green colors are showing air moving toward the right-hand side of the picture, or toward the radar. If you pretend there is a beach ball between the two colors (near the yellow circle and red triangle) you can image the beach ball is spinning. This is a supercell thunderstorm, or mesocyclone, as we detected on our radar. The yellow circle is a computer algorithm detected mesocyclone. The red triangle is a computer algorithm detected tornado vortex signature (TVS).

As a result, we issued a Tornado Warning at 4:13 PM MDT. The warning text can be seen below.

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE RAPID CITY SD
413 PM MDT MON JUL 10 2000
THE NATIONAL WEATHER SERVICE IN RAPID CITY SD HAS ISSUED A
* TORNADO WARNING FOR...
EXTREME SOUTHEASTERN LAWRENCE COUNTY IN WEST CENTRAL SOUTH DAKOTA
* UNTIL 445 PM MDT
* AT 408 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
TORNADIC THUNDERSTORM 5 MILES NORTHWEST OF NEMO...OR ABOUT 12 MILES
SOUTH OF STURGIS...MOVING SOUTHEAST AT 10 MPH.
* SOME LOCATIONS AFFECTED
NEMO AROUND 435 PM MDT
MOVE QUICKLY TO A STURDY INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR
HOME OR BUSINESS. ABANDON YOUR CAR OR MOBILE HOME FOR A STRONGER
SHELTER.
LAT...LON 4426 10362 4418 10360 4419 10346 4426 10346

We have yet confirm a tornado on this storm, be we received numerous reports of a rotating wall cloud. A rotating wall cloud almost always precedes a tornado. We did have numerous reports of large hail with this supercell thunderstorm ranging in size from peas to slightly larger than golf balls. You can see the storm report below of severe weather we had on that Monday.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE RAPID CITY SD
333 PM MDT TUE JUL 11 2000
TIME(MDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
....COUNTY LOCATION....
0350 PM    8 S STURGIS               SD   .75 INCH HAIL
07/10/00 LAWRENCE LOTS OF DIME SIZE HAIL.
REPORTED BY STORM
SPOTTER.
0400 PM 4 NW TILFORD SD 1.75 INCH HAIL
07/10/00 MEADE REPORTED BY MEDIA.
0437 PM PIEDMONT SD .75 INCH HAIL
07/10/00 MEADE REPORTED BY FIRE AND
RESCUE.
0458 PM 3 SE PIEDMONT SD 60 MPH TSTM GUST
07/10/00 MEADE REPORTED BY OFF-DUTY
NWS EMPLOYEE.
0505 PM 3 SE PIEDMONT SD 1 INCH HAIL
07/10/00 MEADE REPORTED BY OFF-DUTY
NWS EMPLOYEE.
0507 PM 3 SE PIEDMONT SD 1.5 INCH HAIL
07/10/00 MEADE REPORTED BY OFF-DUTY
NWS EMPLOYEE.
0507 PM BLACK HAWK SD 1 INCH HAIL
07/10/00 MEADE REPORTED BY EMERGENCY
MANAGEMENT.
0507 PM 6 NW RAPID CITY SD 2 INCH HAIL
07/10/00 PENNINGTON REPORTED BY MEDIA.
0510 PM 1 N BLACK HAWK SD .75 INCH HAIL
07/10/00 MEADE REPORTED BY OFF-DUTY
NWS EMPLOYEE. AT EXIT
50 OF INTERSTATE 90
0510 PM 1 N BLACK HAWK SD .75 INCH HAIL
07/10/00 MEADE AT EXIT 50 OF
INTERSTATE 90. REPORTED
BY OFF-DUTY NWS EMPLOYEE.
0511 PM 2 NE SILVER CITY SD .75 INCH HAIL
07/10/00 PENNINGTON REPORTED BY STORM
SPOTTER.
0525 PM PIEDMONT SD .88 INCH HAIL
07/10/00 MEADE REPORTED BY OFF-DUTY
NWS EMPLOYEE.
0610 PM 10 W UPTON WY 60 MPH TSTM GUST
07/10/00 WESTON REPORTED BY STORM
SPOTTER.
0710 PM HISEGA SD FLOOD
07/10/00 PENNINGTON MINOR FLOODING REPORTED
IN THE HISEGA AREA
ALONG RAPID CREEK.
0750 PM OSAGE WY .75 INCH HAIL
07/10/00 WESTON REPORTED BY EMERGENCY
MANAGEMENT.
0750 PM 20 SE WRIGHT WY .75 INCH HAIL
07/10/00 CAMPBELL REPORTED BY STORM
SPOTTER.
0755 PM 12 S UPTON WY .75 INCH HAIL
07/10/00 WESTON REPORTED BY STORM
SPOTTER.
0830 PM 6 SE ROCKYPOINT WY WIND DAMAGE
07/10/00 CROOK LARGE TREES BLOWN DOWN.
HAY FEEDER TIPPED OVER.
REPORTED BY STORM
SPOTTER.
0915 PM 10 NE UPTON WY 60 MPH TSTM GUST
07/10/00 WESTON PATIO FURNITURE BLOWN
AWAY. REPORTED BY
STORM SPOTTER.

Wall Cloud Near Blackhawk, SD

Return to Weather Gallery


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.