Chase 2010 - Day 30 Discussion

[Nick F]

With the team overnighting in Lamar in SE Colorado, they shouldn't have too far to go to get on some storms today. Looks like a classic DCVZ (Denver Convergence Vorticity Zone) setting up today, with absence of any other forcing mechanisms today (i.e. fronts or defined dryline), this will be the main focus for storm development over the High Plains of eastern Colorado.

I would probably head to Limon on the I-70 and see what happens.

Low probabilities for tornadoes from SPC (2%) - probably because CAPE isn't spectacular on NWP, but the team may see some landspouts develop from storms forming along the DCVZ.

WRF/NAM breaks out precip east of the Front Range across Ern Colorado by 00z (18z CDT), also some fairly decent shear to play with with low-level SE flow, SW flow aloft and convergence too:

Today's SPC Day 1 outlook:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1221 AM CDT WED MAY 26 2010

VALID 261200Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE HIGH PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE

NORTHEAST...

...SYNOPSIS...

TWO LARGE UPPER LOWS -- ONE OVER THE ERN PACIFIC OFF THE W COAST AND

THE OTHER MOVING SWD ACROSS THE CANADIAN MARITIMES -- WILL REMAIN

THE MOST OBVIOUS/SIGNIFICANT FEATURES ALOFT THIS PERIOD.

MEANWHILE...WEAKER LOWS/TROUGHS WILL MOVE NEWD ACROSS THE CANADIAN

PRAIRIE...LINGER JUST OFF THE SOUTHEAST U.S. COAST...AND SHIFT NEWD

ACROSS THE MID MO VALLEY REGION DURING THE AFTERNOON.

AT THE SURFACE...A COLD FRONT WILL MOVE SLOWLY EWD ACROSS THE

WEST...WHILE A BACKDOOR COLD FRONT SHIFTS SWWD ACROSS THE NORTHEAST

STATES. IN BETWEEN...A WEAK FRONTAL ZONE WILL LINGER FROM THE UPPER

GREAT LAKES REGION SWWD ACROSS THE MID MS/MID MO VALLEYS...AND THEN

WWD ACROSS KS INTO THE CENTRAL HIGH PLAINS.

...HIGH PLAINS...

SELY FLOW ACROSS THE HIGH PLAINS WILL CONTINUE TO SUPPLY RELATIVELY

MOIST LOW-LEVEL AIR...WHICH -- WHEN SUBJECTED TO DAYTIME HEATING --

WILL BECOME MODERATELY UNSTABLE. BY AFTERNOON...EXPECT ISOLATED TO

SCATTERED STORM DEVELOPMENT TO OCCUR ALONG THE HIGH

PLAINS...EVENTUALLY EXTENDING FROM MT SWD TO NM.

WHILE NOT EXCEPTIONALLY STRONG...LOW-LEVEL SELYS BENEATH MID-LEVEL

SWLYS WILL YIELD SHEAR SUFFICIENT FOR ORGANIZED/ROTATING

STORMS...AND THUS THREAT FOR LARGE HAIL AND LOCALLY DAMAGING WINDS

IS EXPECTED WITH STRONGER STORMS. STORMS SHOULD CONTINUE OVERNIGHT

AS LOW-LEVEL JET INCREASES -- PARTICULARLY INTO MT WHERE AN

EWD-MOVING MCS MAY DEVELOP IN CONJUNCTION WITH A 40 KT-PLUS ESELY

LOW-LEVEL JET.

[Nick F]

13z update has increased tornado probs to 5% and hail to 30% from SE Colorado northwards:

...HIGH PLAINS/NM TO MT...

MID LEVEL SPEED MAX ROTATING THROUGH THE BASE OF LARGER SCALE TROUGH

WILL SPREAD INLAND FROM SRN CA TO THE INTERMOUNTAIN WEST THIS

PERIOD. GRADUAL INCREASE IN THE SWLY MID LEVEL FLOW WILL COINCIDE

WITH DIURNAL AND DIFFERENTIAL HEATING OVER THE FRONT RANGE AND ERN

SLOPES OF THE ROCKIES WITH MOIST LOW LEVEL SELY UPSLOPE FLOW

STRENGTHENING THROUGH THE DAY.

BY 21Z...EXPECT SBCAPE VALUES TO RANGE FROM ABOUT 1000 J/KG OVER

SERN MT TO AROUND 2000 J/KG ACROSS SERN NM. STORMS ARE LIKELY TO

INITIATE ACROSS THIS ENTIRE EXTENSIVE REGION. STRONGER 0-6KM SHEAR

OF 30-40KT IS FORECAST FROM CO TO WY WHERE A FEW TO SEVERAL

SUPERCELLS COULD DEVELOP WITH ATTENDANT THREATS OF HAIL/WIND AND

TORNADOES. INCREASING LARGE SCALE FORCING FOR ASCENT WILL DEVELOP

ACROSS MT WHERE STORMS SPREADING OFF HIGHER TERRAIN MAY BE

MAINTAINED WELL AFTER DARK...DEVELOPING EAST ALONG INSTABILITY

GRADIENT FROM ERN MT INTO ND...IN THE FORM OF AN MCS WITH WIND AND

HAIL.

STORMS FROM SERN CO TO NM WILL ALSO POSE A THREAT OF SEVERE

WIND/HAIL AND PERHAPS A TORNADO BUT WILL EXIST IN SLIGHTLY WEAKER

FLOW/SHEAR...COINCIDENT WITH LARGE SCALE HEIGHT RISES. THIS SUGGESTS

THAT THIS ACTIVITY WILL BE PRIMARILY DIURNAL IN NATURE AND DECAY

WITHIN A COUPLE HOURS AFTER SUNSET.

[nsrobins]

Stu Robinson's presentation on the DCVZ at last Autumn's Torro meeting illustrated how potent this mechanism can be when, as Nick says, most other drivers appear to be absent. Will certainly be worth a look. It was interesting to see so few chasers on the road yesterday despite what appeared to be, and ultimately turned out to be, quite a resonable event.

Hope it's as profitable today.

[ANYWEATHER]

Indeed ,Nick, looks favourable for the DCVZ and Limon is the place to sit and wait for this to develop! I think Im right in saying that Limon or a place nearby was devastated by a tornado some years back. Eastern Colorado is home to about 9 months of the year of Tornadic storms although many of them nonsupercell tornadic storms, but generally these storms have slow storm motions so good for photography etc! Anyway judging by the latest gfs output there could well be a few chases around that area in the coming days.... guys and gals best of luck to everyone.

[gpspete]

Indeed ,Nick, looks favourable for the DCVZ and Limon is the place to sit and wait for this to develop! I think Im right in saying that Limon or a place nearby was devastated by a tornado some years back. Eastern Colorado is home to about 9 months of the year of Tornadic storms although many of them nonsupercell tornadic storms, but generally these storms have slow storm motions so good for photography etc! Anyway judging by the latest gfs output there could well be a few chases around that area in the coming days.... guys and gals best of luck to everyone.

Limon Tornado June 6th 1990 8:10pm

[NL]

Mesoscale discussion and the team are in prime position..!!

MESOSCALE DISCUSSION 0717

NWS STORM PREDICTION CENTER NORMAN OK

0226 PM CDT WED MAY 26 2010

AREAS AFFECTED...CENTRAL HIGH PLAINS

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 261926Z - 262030Z

BOUNDARY LAYER MOISTURE IS GRADUALLY SPREADING NWWD ACROSS THE CNTRL

HIGH PLAINS AS SELY FLOW INCREASES ON BACK SIDE OF CNTRL U.S. RIDGE.

SFC DEW POINTS HAVE NOW RISEN INTO THE MID 50S ACROSS MUCH OF ERN

CO/WY WHERE AN AXIS OF MLCAPE APPROACHING 1500 J/KG EXTENDS FROM THE

CO/KS BORDER...NWWD INTO NERN WY.

LATEST VIS SATELLITE IMAGERY SUPPORTS THIS GRADUAL DESTABILIZATION

WITH BOUNDARY LAYER CU FIELD EXPANDING/DEEPENING ACROSS THE UPSLOPE

REGIONS. MORE RECENTLY ISOLATED THUNDERSTORMS HAVE DEVELOPED ALONG

A WWD SURGING OUTFLOW BOUNDARY ACROSS THE TX/OK PANHANDLES...NWWD

INTO SERN CO. OTHER ACTIVITY IS DEVELOPING NEAR DEN...AND WITH TIME

DEEP CONVECTION SHOULD EVOLVE OFF THE LARAMIE RANGE. ALTHOUGH DEEP

LAYER SHEAR IS NOT THAT STRONG...VEERING PROFILES SHOULD SUPPORT

ROTATING UPDRAFTS AND SUPERCELLS. LARGE HAIL IS LIKELY WITH THE

STRONGER STORMS...AND PERHAPS A COUPLE OF TORNADOES.

Tornado warning already on a storm around 150 mile to the NW of the team.

192

WFUS55 KBOU 261931

TORBOU

COC001-031-262015-

/O.NEW.KBOU.TO.W.0025.100526T1931Z-100526T2015Z/

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE DENVER CO

131 PM MDT WED MAY 26 2010

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A

* TORNADO WARNING FOR...

WEST CENTRAL ADAMS COUNTY IN NORTHEAST COLORADO

NORTHEASTERN DENVER COUNTY IN NORTHEAST COLORADO

* UNTIL 215 PM MDT

* AT 132 PM MDT...A SEVERE THUNDERSTORM WAS REPORTED OVER CENTRAL

COMMERCE CITY...OR 12 MILES NORTHEAST OF DENVER. THIS STORM WAS

MOVING NORTH AT 10 MPH.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO BRIGHTON...

BARR LAKE...NORTHWESTERN DENVER INTERNATIONAL AIRPORT...

NORTHEASTERN THORNTON AND NORTHEASTERN COMMERCE CITY.

Latest visible satellite image.

[NL]

Tornado watch just about to be issued .

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 223

NWS STORM PREDICTION CENTER NORMAN OK

150 PM MDT WED MAY 26 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

NORTHEAST COLORADO

THE WESTERN NEBRASKA PANHANDLE

EASTERN WYOMING

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 150 PM UNTIL

900 PM MDT.

TORNADOES...HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 60 STATUTE

MILES EAST AND WEST OF A LINE FROM 25 MILES WEST NORTHWEST OF

GILLETTE WYOMING TO 50 MILES SOUTH OF LIMON COLORADO. FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU3).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.

DISCUSSION...LOW-LEVEL MOISTURE CONTINUES TO SPREAD NWWD ACROSS THE

HIGH PLAINS AS SURFACE TEMPERATURES WARM WITH DAYTIME HEATING.

THESE PROCESSES HAVE CONTRIBUTED TO A MODERATELY UNSTABLE

ENVIRONMENT WITH WEAKENING CONVECTIVE INHIBITION...AS EVIDENCED BY

THE RECENT STORM DEVELOPMENT NEAR DENVER...AND OTHER DEEPENING

CUMULUS NEAR THE LARAMIE RANGE IN WY. EXPECT STORM

COVERAGE/INTENSITY TO INCREASE THROUGH THE AFTERNOON...WITH VERTICAL

SHEAR SUFFICIENT FOR SLOW-MOVING SUPERCELLS WITH LARGE HAIL AND

DAMAGING WINDS. ADDITIONALLY...LOW-LEVEL SHEAR WILL GRADUALLY

INCREASE BY THIS EVENING IN A SUFFICIENTLY MOIST ENVIRONMENT TO

SUPPORT THE THREAT FOR A FEW TORNADOES.

WWUS40 KWNS 261950

WWP3

TORNADO WATCH PROBABILITIES FOR WT 0223

NWS STORM PREDICTION CENTER NORMAN OK

0250 PM CDT WED MAY 26 2010

WT 0223

PROBABILITY TABLE:

PROB OF 2 OR MORE TORNADOES : 60%

PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 20%

PROB OF 10 OR MORE SEVERE WIND EVENTS : 20%

PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 20%

PROB OF 10 OR MORE SEVERE HAIL EVENTS : 70%

PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : 50%

PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : 90%

&&

ATTRIBUTE TABLE:

MAX HAIL /INCHES/ : 2.5

MAX WIND GUSTS SURFACE /KNOTS/ : 60

MAX TOPS /X 100 FEET/ : 500

MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 20015

PARTICULARLY DANGEROUS SITUATION : NO

[Nick F]

Tornado warning tracking a tornado over Northern Denver International Airport:

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE DENVER CO

206 PM MDT WED MAY 26 2010

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A

* TORNADO WARNING FOR...

CENTRAL ADAMS COUNTY IN NORTHEAST COLORADO

NORTHEASTERN DENVER COUNTY IN NORTHEAST COLORADO

EXTREME SOUTH CENTRAL WELD COUNTY IN NORTHEAST COLORADO

* UNTIL 245 PM MDT

* AT 206 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING

A TORNADO OVER NORTHERN DENVER INTERNATIONAL AIRPORT...OR 17 MILES

NORTHEAST OF DENVER. THIS STORM WAS MOVING NORTHEAST AT 5 MPH.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO LOCHBUIE...

BARR LAKE...NORTHERN DENVER INTERNATIONAL AIRPORT AND NORTHEASTERN

COMMERCE CITY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A

STURDY BUILDING. AVOID WINDOWS. IF IN A MOBILE HOME...A VEHICLE OR

OUTDOORS...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT

YOURSELF FROM FLYING DEBRIS.

&&

LAT...LON 3996 10456 3988 10461 3985 10469 3988 10479

3996 10478 4003 10474 4002 10462

TIME...MOT...LOC 2006Z 215DEG 6KT 3989 10471

[Tom Lynch]

I bet you lot are enjoying this. I am enjoying watching it unfold.

Tom

[Tom Lynch]

Yes chaps that cell you are heading towards looks atm to be the best option. Has shown great promise slow moving , rotaion. I hope you are sucessful with this one.

Tom

[davehsug]

Yes chaps that cell you are heading towards looks atm to be the best option. Has shown great promise slow moving , rotaion. I hope you are sucessful with this one.

Tom

Can you see this Tom? I've had the loading symbol for nearly an hour now.

[dallas]

Can you see this Tom? I've had the loading symbol for nearly an hour now.

Yeah me too

stream is now back

[Roger J Smith]

Any sign of balloon boy?

Well, it's a bonus for the tour to have a view (perhaps) of the Rockies, if not this evening, then possibly tomorrow morning.