StormTrack: July 17: Tornadic Thunderstorm near Minot, ND

Wind Velocities

Maximum Hail Size

From The Weather Centre's Mobile StormTrack Team,
The Weather Centre has issued a Special Weather Warning for
Sawyer, ND

At 10:24 AM... A thunderstorm with a previous tornado warning and maximum hail size of 3.25 inches was located tracking into Sawyer, North Dakota.

People in this area are advised to prepare for life threatening hail and a potential tornado.

Tornado plans are advised to be put into effect at this time as safety conditions are being compromised.

This warning will expire at 10:45 AM.

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Our 2011-2012 Winter Outlook map has been redesigned with new maps that will be useful in the long run.

July 17: Tornado Warning- Near Minot, ND

...A TORNADO WARNING REMAINS IN EFFECT FOR SOUTHEASTERN WARD COUNTY
UNTIL 1030 AM CDT...

AT 1000 AM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO.  THIS DANGEROUS
STORM WAS LOCATED 11 MILES EAST OF RICE LAKE...OR 16 MILES SOUTH OF
MINOT...MOVING EAST AT 40 MPH.

LOCATIONS IMPACTED INCLUDE...
  SAWYER.

Severe Thunderstorm Watch #650

THE NWS STORM PREDICTION CENTER HAS ISSUED A
   SEVERE THUNDERSTORM WATCH FOR PORTIONS OF 
   
          NORTHWEST MINNESOTA
          NORTHERN AND EASTERN NORTH DAKOTA
   
   EFFECTIVE THIS SUNDAY MORNING AND AFTERNOON FROM 955 AM UNTIL 500
   PM CDT.
   
   HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80
   MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
   
   THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 65
   STATUTE MILES NORTH AND SOUTH OF A LINE FROM 90 MILES WEST OF
   DEVILS LAKE NORTH DAKOTA TO 20 MILES NORTHEAST OF BEMIDJI
   MINNESOTA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
   ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).
   
   REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
   FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
   AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
   THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
   AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
   DO PRODUCE TORNADOES.
   
   DISCUSSION...A PERSISTENT CLUSTER OF TSTMS NEAR MINOT HAS SHOWN
   SIGNS OF INTENSIFICATION IN THE PAST 30 MINUTES.  THOUGH CONVECTIVE
   INHIBITION STILL REMAINS SUBSTANTIAL FOR SURFACE-BASED PARCELS...THE
   DOWNSTREAM ENVIRONMENT IS EXTREMELY UNSTABLE ACROSS ND...AND MLCAPE
   WILL LIKELY EXCEED 6000 J/KG WITH ADDITIONAL DAYTIME HEATING BY
   EARLY-MID AFTERNOON.  MEANWHILE...A WELL-DEFINED SPEED MAX IS
   CRESTED THE RIDGE FROM NE MT INTO NW ND...AND ASCENT IN ADVANCE OF
   THIS WAVE WILL HELP SUPPORT UPSCALE GROWTH OF THE STORM CLUSTER AS
   IT MOVES EWD ALONG A RESIDUAL SURFACE BOUNDARY INTO E/NE ND. 
   VERTICAL SHEAR AND INSTABILITY WILL SUPPORT BOTH SUPERCELLS AND BOW
   ECHOES WITH THE POTENTIAL FOR VERY LARGE HAIL AND DAMAGING GUSTS. 
   AN ISOLATED TORNADO CANNOT BE RULED OUT...ESPECIALLY BY AFTERNOON AS
   THE BOUNDARY LAYER WARMS/DESTABILIZES.  OTHERWISE...THE STORMS COULD
   GROW UPSCALE INTO A BOWING MCS...WITH THE POTENTIAL FOR MORE
   WIDESPREAD AND SIGNIFICANT WIND DAMAGE THIS AFTERNOON.
   
   AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
   TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70
   KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 650. MEAN STORM
   MOTION VECTOR 28035.

StormTrack: July 17: Iowa Single-Cell Storms (Morning)

The Weather Centre is tracking thunderstorms in Iowa.

TERMS TO KNOW
CAPE: A measure of instability. 2000+ values considered unstable.
LI: Lifted Index- another measure of instability. Negative values considered unstable.
EHI: Energy Helicity Index. A measure of tornado potential.
VGP: Vorticity Generation Potential
SRH: Storm Relative Helicity. Detects cyclonic motion in thunderstorm updrafts. Considered dangerous at levels above 200.

Looking at current observations, I am seeing the atmosphere as dangerous. It looks like the Lifted Index (A measure of instability) is down into -10, which is very unstable. That coupled with CAPE values of over 5000, makes the atmosphere very rambunctious.  One more concerning thing is something called an EHI. Thunderstorms form when warm air rises vertically. Energy. That's the E in EHI. Helicity is the spinning motion that could occur as this warm air rises, priming the environment for potential tornadoes. That's the H. Put them together and we have the Energy Helicity Index. EHI combines both CAPE and Helicity.  SRH values are currently at 250 in North Iowa.

All this information put together indicates a tornado potential. However, there are several roadblocks. Shearing is nonexistent in some parts of North Iowa. That kills tornado potential and basically ends hope for tornadoes. But then again, you never know if these parameters do indicate a tornado could occur.