Tuesday, July 19, 2011

July 19: MCS in North Wisconsin

MCS (Mesoscale Convective System) on radar
A MCS (storm cluster) is currently moving southeast from North Wisconsin.

Discussion... 1z RUC has evolved this system quite nicely at this time. RUC 1z run weakens MCS rapidly over the next couple hours as it moves more ESE towards Lake Michigan.
Looking over current CINH/CAPEs, it looks like the MCS is entering an area of CINH, or a warm air layer aloft, that suppresses storm development.
This CINH will likely put down the storm strength. However, the reason while this MCS will likely take a ESE turn is because the hot ridge that is creating the massive intense heat wave will be moving east, thus changing the storm track farther east.
Will keep storm potential at SLGT CHC to CHC in areas like North Illinois, while portions of Michigan will have a slightly higher POPS (Probability of Precipitation), possibly reaching into CHC of precipitation.

July 19: Tornadic Weather Situation (Northwest Wisconsin)- Part 2


THE NATIONAL WEATHER SERVICE IN THE TWIN CITIES HAS ISSUED A

* TORNADO WARNING FOR...
  WESTERN BARRON COUNTY IN NORTHWEST WISCONSIN...

* UNTIL 830 PM CDT

* AT 729 PM CDT...RADAR INDICATED A STORM CAPABLE OF PRODUCING A
  TORNADO. THE MOST DANGEROUS PART OF THE STORM WAS 9 MILES NORTHWEST
  OF COMSTOCK...OR ABOUT 4 MILES SOUTHWEST OF MCKINLEY...AND MOVING
  SOUTHEAST AT 20 MPH.

* LOCATIONS IN THE WARNING INCLUDE...
  CUMBERLAND...
  COMSTOCK...
  TURTLE LAKE...
  PRAIRIE FARM...
  ALMENA...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

WHEN A TORNADO WARNING IS ISSUED BASED ON RADAR...IT MEANS THAT
STRONG ROTATION HAS BEEN DETECTED IN THE STORM. A TORNADO MAY ALREADY
BE ON THE GROUND...OR IS EXPECTED TO DEVELOP SHORTLY.

July 19: Tornadic Weather Situation (Northwest Wisconsin)



We've got a few tornadic thunderstorms going on this evening across Northwest Wisconsin.
All 3 of the above images are storms currently tornado warned, and the one i'm most concerned about is the second image.
It's never good to see that couplet on the radar. What the couplet indicates are winds going in opposite directions intercepting in one spot.
That situation usually indicates strong circulation and spawns tornadoes.

That said, the following cities should take cover now.
-Owens, WI
-Dorchester, WI
-Abbotsford, WI
-Curtiss, WI
-Balsam Lake, WI
-McKinley, WI
-Range, WI
-Joel, WI
-Clayton, WI

ALL of Illinois now under an Excessive Heat Warning

All of Illinois is now under an Excessive Heat Warning.
It joins Iowa in becoming a state completely covered by Excessive Heat Warnings.

Weather Alert: Severe Weather July 19 (Wisconsin, Illinois, Iowa)

Follow Up: July 19: Mesoscale Discussion #1662- North Illinois, East Iowa, Southwest Wisconsin

The Weather Centre has begun an experimental test of an outlining procedure for areas at risk for any form of weather phenomena.

THE WEATHER CENTRE HAS ISSUED A WEATHER ALERT FOR:
-ILLINOIS
-IOWA
-WISCONSIN

(SEE ABOVE LINK FOR PRE-READING BRIEFING)

BEGIN STATEMENT

THE WEATHER CENTRE HAS IDENTIFIED AN AREA IN THE OUTLINED REGION AT RISK FOR A FORM OF POTENTIALLY HAZARDOUS WEATHER.

ILLINOIS...IOWA...AND WISCONSIN ARE AT RISK FOR HEAVY RAINFALL AND DAMAGING WINDS THROUGH THIS EVENING.

DISCUSSION... HIGH CAPES AND HIGH PWAT READINGS HAVE LED THE WEATHER CENTRE TO ISSUE A PUBLIC WEATHER ALERT.
STORM DEVELOPMENT IS EXPECTED IN THE NEAR FUTURE. THESE STORMS WILL HAVE POTENTIAL FOR DAMAGING WINDS AND ESPECIALLY HEAVY RAINFALL. WITH PWAT VALUES ABOVE 2 INCHES... THE RISK FOR FLASH FLOODING HAS SKYROCKETED.

WE WILL CONTINUE MONITORING THIS SITUATION AND PROVIDE UPDATES AS NEEDED.

END STATEMENT

ABOVE STATEMENT INTENDED FOR PUBLIC INFORMATION.

July 19: Mesoscale Discussion #1662- North Illinois, East Iowa, Southwest Wisconsin

A Mesoscale Discussion has been issued for North Illinois, East Iowa and Southwest Wisconsin.
CAPE values are above 7000 right now, indicative of a very unstable air mass. Within this MCD is a channel of higher PWAT (Precipitable Water) than that of surrounding areas. For those unfamiliar with PWAT values, it's when a meteorologist on TV says there's X many inches of water in the air.
Anyways, PWAT values reach above 2 inches in this narrow channel, indicating some heavy rain is possible in these areas.
While current wind gusts and sustained winds are not impressive, a nearby stationary front up in the Wisconsin portion of this MCD (Mesoscale Discussion) will likely enact at least a portion of the damaging wind threat.

If a watch is issued, it looks like it will be a severe thunderstorm watch, and we will post that when it comes out.

Weather Extremes: Incredible Supercell Composite Values July 19

StormTrack: July 19: Minneapolis Severe Thunderstorm

VIL

Composite Reflectivity
There is a severe thunderstorm moving into Minneapolis and St. Paul at this time. Below is the severe thunderstorm warning.


...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT FOR RAMSEY...
NORTHEASTERN HENNEPIN AND ANOKA COUNTIES UNTIL NOON CDT...

AT 1059 AM CDT...NATIONAL WEATHER SERVICE RADAR INDICATED A SEVERE
THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND DESTRUCTIVE
WINDS IN EXCESS OF 70 MPH.  THIS STORM WAS LOCATED NEAR COON
RAPIDS...OR 14 MILES NORTHEAST OF PLYMOUTH...MOVING SOUTHEAST AT 30
MPH.

LOCATIONS IMPACTED INCLUDE...
  MINNEAPOLIS...ST PAUL...BROOKLYN PARK...BLAINE...SPRING LAKE
  PARK...BROOKLYN CENTER...LEXINGTON...CRYSTAL...FRIDLEY...CIRCLE
  PINES...MOUNDS VIEW...LINO LAKES...ROBBINSDALE...CENTERVILLE AND
  HILLTOP.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

THIS IS A DANGEROUS SITUATION. IF YOU ARE IN THE PATH OF THIS
STORM...PREPARE IMMEDIATELY FOR DESTRUCTIVE WINDS...WHICH CAN UPROOT
TREES...DOWN POWER LINES...AND CAUSE DAMAGE TO ROOFS AND WINDOWS.
EVACUATE MOBILE HOMES AS THEY MAY BE OVERTURNED. LARGE HAIL IS ALSO
EXPECTED...WHICH CAN CAUSE DAMAGE TO VEHICLES AND WINDOWS. SEEK
SHELTER NOW INSIDE A STURDY STRUCTURE AND STAY AWAY FROM WINDOWS.

THIS STORM HAS EXHIBITED SOME WEAK ROTATION. TORNADOES CAN DEVELOP
QUICKLY FROM SEVERE THUNDERSTORMS. ALTHOUGH ONE IS NOT IMMEDIATELY
LIKELY...IF A TORNADO IS SPOTTED...ACT QUICKLY AND MOVE TO A PLACE OF
SAFETY INSIDE A STURDY STRUCTURE... SUCH AS A BASEMENT OR SMALL
INTERIOR ROOM.

Looking at the images at the top of the page, VIL's (parameter indicating hail) are very high in the region specified, indicating very large hail may be occurring.

Below is an image depicting maximum hail sizes could reach 2 inches.

July 19: Severe Thunderstorm Watch #662

A severe thunderstorm watch has been issued for a very strong thunderstorm cell and associated cluster of showers and thunderstorms.
This watch goes from now to 3:00 PM CDT for the areas outlined above.
Since this thunderstorm appears to be very strong and healthy, let's see if it could go tornadic or supercellular.
Below (in order) are the Supercell Composite, Significant Tornado Parameter, and Energy-Helicity Index images for this area.
Supercell Composite (SCP). Higher values indicate more likelihood for supercells.

STP. Values above 1 have been associated with EF2+ tornadoes

EHI. Dangerous levels begin at 2 units.
These above images (in order) tell if the storm will go supercellular, what chance it has of going tornadic, and how much energy combined with spinning motion the atmosphere has.

These images tell that the storm is in an unfavorable environment for tornadoes, thus only the severe thunderstorm watch instead of a tornado watch.
This storm probably won't produce a tornado judging by only these parameters, and hodographs (weather balloons that indicate spinning in the atmosphere) aren't impressive.

July 19 Severe Weather Discussion- Conditional Storm Action Day Declared

Today's Severe Weather Threat
Today's Hail Outlook

Today's Tornado Outlook

Today's High Wind Threat
A Conditional Storm Action Day has been declared because today's severe threat covers such a large area.




...THERE IS A SLGT RISK OF SVR TSTMS FROM THE NRN ROCKIES EWD INTO
   THE UPPER GREAT LAKES AND SEWD INTO THE CNTRL APPALACHIANS TO MID
   ATLANTIC COAST...
   
   ...NRN ROCKIES EWD ACROSS MT...
   
   POTENT SHORT WAVE TROUGH AND ATTENDING 50-60 KT MIDLEVEL JET STREAK
   WILL PROGRESS NEWD ACROSS THE REGION DURING THE D1 PERIOD ALONG WITH
   ACCOMPANYING PACIFIC FRONT.  STEEP MIDLEVEL LAPSE RATES ATOP
   BOUNDARY LAYER DEWPOINTS IN THE 50S WILL YIELD A MODERATELY UNSTABLE
   AIR MASS BY AFTERNOON WITH MLCAPE INCREASING TO 1000-1500 J/KG. 
   TSTMS WILL INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON AND
   TONIGHT INVOF SURFACE FRONT AND FAVORED TERRAIN AS LARGE-SCALE
   FORCING ASSOCIATED WITH MIDLEVEL TROUGH OVERSPREADS DESTABILIZING
   AIR MASS.  VERTICALLY VEERING WIND PROFILES ACROSS WARM SECTOR WILL
   FAVOR THE DEVELOPMENT OF SUPERCELLS IN ADDITION TO BOWING STRUCTURES
   WITH A RISK FOR MAINLY DAMAGING WINDS AND HAIL SPREADING EWD INTO
   THE NRN HIGH PLAINS TONIGHT.
   
   ...NRN PLAINS INTO UPPER GREAT LAKES AND MIDWEST...
   
   WHILE MIDLEVEL HEIGHTS WILL BEGIN TO LOWER OVER THE DAKOTAS DURING
   THE LATTER HALF OF THE FORECAST PERIOD...LARGE-SCALE FORCING FOR
   ASCENT WILL REMAIN NEGLIGIBLE FARTHER E/SE.  IN THE LOW
   LEVELS...WEAK SURFACE LOW OBSERVED OVER N-CNTRL SD MAY PERSIST
   THROUGH THE DAY ALONG SURFACE BOUNDARY WHICH WILL RETREAT NWD AS A
   WARM FRONT IN RESPONSE TO DEEPENING LEE CYCLONE PROGRESSING THROUGH
   CNTRL/ERN MT.
   
   CLUSTERS OF MAINLY ELEVATED TSTMS ARE ONGOING ACROSS PORTIONS OF ERN
   ND/NRN MN...DRIVEN BY WAA TO THE N/NE OF SURFACE FRONT AND WITHIN
   EXIT REGION OF SWLY LLJ.  HAIL AND LOCALLY DAMAGING WIND GUSTS WILL
   BE POSSIBLE WITH THESE STORMS THROUGH MID MORNING BEFORE ACTIVITY
   WEAKENS WITH THE DIURNAL CESSATION OF LLJ.  THEREAFTER...TSTM
   DEVELOPMENT AND EVOLUTION BECOMES MUCH MORE UNCERTAIN OWING TO THE
   WEAKLY FORCED ENVIRONMENT.  CURRENT INDICATIONS ARE THAT SEGMENT OF
   SURFACE BAROCLINIC ZONE EXTENDING FROM THE WRN DAKOTAS INTO MN HAS
   THE HIGHEST PROBABILITY OF EXPERIENCING SEVERE STORMS THIS AFTERNOON
   INTO TONIGHT.  INCREASING HEIGHT FALLS/DYNAMIC FORCING FOR ASCENT
   WILL BE THE PRIMARY FORCING MECHANISM LATER TODAY ACROSS WRN ND WITH
   INCREASING LOW-LEVEL WAA AT TERMINUS OF DEVELOPING 30-40 KT LLJ THE
   MAIN FOCUS FOR STORMS FARTHER E.
   
   AMBIENT ENVIRONMENT INVOF WARM FRONT WILL BE CHARACTERIZED BY A VERY
   MOIST BOUNDARY LAYER BENEATH STEEP MIDLEVEL LAPSE RATES...YIELDING
   MLCAPE VALUES 2500-5000 J/KG.  DEEP-LAYER VERTICAL SHEAR WILL NOT BE
   PARTICULARLY STRONG /I.E. LESS THAN 35 KT/...HOWEVER VERTICALLY
   VEERING WINDS INVOF SURFACE BOUNDARY WILL SUPPORT ORGANIZED STORM
   STRUCTURES CAPABLE OF LARGE HAIL...DAMAGING WINDS AND PERHAPS A
   TORNADO.
   
   ...OH VALLEY INTO THE CNTRL APPALACHIANS AND MID ATLANTIC COAST...
   
   WEAK MIDLEVEL PERTURBATIONS /SOME OF CONVECTIVE ORIGIN/ WILL
   PROGRESS SEWD ACROSS REGION TODAY WITHIN DIFFLUENT MIDLEVEL FLOW
   REGIME.  IN THE LOW LEVELS...A SWD-MOVING COLD FRONT AND EXISTING
   OUTFLOW BOUNDARIES WILL SERVE AS THE FOCI FOR DIURNAL TSTM
   DEVELOPMENT...SOME OF WHICH COULD BE SEVERE.
   
   TSTMS ONGOING ACROSS SRN OH INTO WV MAY WEAKEN THIS MORNING AS NWLY
   LLJ OVER THE OH VALLEY DIMINISHES.  RESIDUAL CLOUD DEBRIS MAY TEMPER
   DAYTIME HEATING AT SOME LOCATIONS...WHILE ELSEWHERE STRONGER
   INSOLATION COUPLED WITH A MOIST BOUNDARY LAYER WILL BE SUPPORTIVE OF
   AFTERNOON MLCAPE APPROACHING 1000-2000 J/KG.  VERTICAL SHEAR WILL
   REMAIN RATHER WEAK...THOUGH THE MODERATE INSTABILITY...STEEPENING
   LOW-LEVEL LAPSE RATES AND RELATIVELY MOIST ENVIRONMENT SUGGEST THE
   POTENTIAL FOR STRONG WET MICROBURSTS AND AN ATTENDANT DAMAGING WIND
   THREAT.

July 19- Morning Tropical Storm Dora Update

Tropical Storm Dora currently has maximum sustained winds of 55 MPH, with a central pressure of 996 millibars. Dora is moving west at 16 MPH.
Dora is forecast to rapidly strengthen into a hurricane, and eventually into a major Category 3 hurricane before rapidly cooling down into a tropical storm 5 days out and then likely weakening.

Intensity and ensemble forecasts paint a similar picture, although some models bring the storm a bit too close for comfort to Baja California. We will have to watch that scenario.

Dora is currently not a threat to land but could eventually affect land.

July 19- Morning Tropical Storm Bret Update

Bret is currently a tropical storm with winds of 45 miles per hour. Central pressure is at 1000 millibars. Bret is currently moving North Northeast at 7 MPH.

Bret is now forecast to weaken quicker than originally thought. At this time, Bret is expected to weaken on Friday, probably by evening, below tropical depression status. Bret will supposedly lose tropical storm status sometime on Thursday.


Ensemble and intensity forecasts indicate Bret will lose his tropical storm attributes more slowly. However, Bret has always been a weak storm and on the small side, so I believe the NHC does have a good forecast for Bret at this time.

Bret is not a threat to land.