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View Full Version : Sat/Sun, July 2/3.11


Derecho
06-28-2011, 07:01 PM
Too early to start speculating? :whistling:

Latest DTX AFD for SEMI
SATURDAY LOOKS TO BE THE MORE INTERESTING DAY. A WEAK COLD FRONT
WILL SLOWLY SAG SOUTH ACROSS THE AREA ON SATURDAY. LATEST 12Z GFS
BUFR SOUNDINGS SHOW SBCAPE VALUES CLIMBING TO NEARLY 4000 J/KG.
ALTHOUGH THIS IS LIKELY TOO HIGH GIVEN THE 75+ SURFACE DEWPOINTS
FORECASTED BY THE GFS...MODIFIED SOUNDINGS WITH A 71F SURFACE
DEWPOINT STILL GIVE SBCAPE VALUES AROUND 3000 J/KG WITH CIN VALUES
AROUND 100 J/KG. THIS CAP...ALTHOUGH WEAKER IN THE NORTHERN CWA...IS
SOMEWHAT CONCERNING GIVEN VERY LITTLE SYNOPTIC FORCING WITH THE MAIN
SHORTWAVE WELL NORTH OF THE REGION IN ONTARIO. CHANCES FOR
CONVECTION MAY DEPEND ON UPSTREAM MCS DEVELOPMENT IN ORDER TO
OVERCOME THIS CAP. IF CONVECTION DOES MANAGE TO INITIATE...IT WILL
NOT BE DIFFICULT TO ORGANIZE GIVEN 40+ KNOTS AT 500MB AND 25+ KNOTS
AT 850MB IN A LARGELY UNIDIRECTIONAL WIND PROFILE. DEEPER MIXING AND
A SLIGHTLY WARMER AIRMASS WILL ALLOW HIGH TEMPS ON SATURDAY TO MAKE
A RUN AT THE LOWER 90S BUT THIS IS LARGELY DEPENDENT ON THE TIMING
OF POSSIBLE CONVECTION.

davefootball123
06-28-2011, 11:18 PM
Ya ive been watching the models very closley... Deffenitley a very unstable environment with lots of CAPE and Lifted indicies down to -10 in areas. Shear is also quite favourable. The one thing that i am still watching is 850 mb/surface winds are out of the WSW at 18z and 0z on Saturday. If this is the case im not entirley sure we will have enough forcing along the short wave trough for a large severe weather event. None the less...severe weather seems quite possible with linear segmants/clusters and possible MCS seems to be the probable convective mode if anything were to happen. Also if you take a look at the QPF forecast at 00z Saturday it indicates some fallen precip through much of southwestern ontario and into the GTA....wonder if it thinks there will be some storms too. As for Sunday, I dont expect much. If you look at the forecast MLCAPE and Lifted Indices the best instability is in the States on Sunday towards the east coast.

Smokin Joe
06-29-2011, 03:33 PM
any updates on the situation?

Derecho
06-29-2011, 04:32 PM
The one thing that i am still watching is 850 mb/surface winds are out of the WSW at 18z and 0z on Saturday..

Cold front passage around mid-afternoon according to the SREF

davefootball123
06-29-2011, 06:01 PM
Cold front passage around mid-afternoon according to the SREF

The cold front looks to pass between 12 and 2 on the 15z SREF...NAM is a little later with it coming through after dinner....There now looks to be some 850 mb forcing along the front which is good. Airmass is still looking to be pretty unstable over the southwest with MLCAPES AOA 1500j/kg with lifted indices between -2 and -8 however further east into the Golden horseshoe it appears instability will be less facourable. Shear isnt looking as good as it was but 30-40kts still looks to be reasonable. Main threat appears damaging winds with these storms if any were to form.

Derecho
06-30-2011, 09:00 AM
Looks like my jinxing powers are still going strong :unsure:

Only extreme SW Ontario is in the current day 3 "see text" risk.

Smokin Joe
06-30-2011, 09:30 AM
I'm holding out hope that the risk area will fatten up for sat. over the next couple of days and creep over the border.....but man this is depressing if nothing comes this weekend

EC has Windsor reaching 35c now on saturday from 32 yesterday.......i'm going down if there is any hope

davefootball123
06-30-2011, 04:20 PM
Saturday still could be interesting for a possible line of thunderstorms. Instability is looking fairly good on the latest NAM, GFS and SREF. These models bring the cold front through between 5pm and 12am...Temps and dewpoints still look quite favourable... along with PW values of 1.5 inches or greater, however there isnt alot of favourable shear looks to be about 30kts. And the GFS and NAM hint at a possible cap(warm air aloft between 850 and 700mb limiting storm formation) however if the cap erodes storms are deffeintley possible given the MUCAPES of around 2000j/kg or greater. Still needs to be watched. At the moment i wouldnt be suprised if we got in a slight tomorrow but i may have just jinxed it so ya ;)


EDIT: 18z NAM run gets rid of the cap almost entirley also a little more favourable 0-700mb shear is starting to show up hinting at some possible damaging winds with a line that may form...have to watch this one for sure

Derecho
06-30-2011, 06:38 PM
A great AFD from DTX, it sounds promising.


UPPER LEVEL WAVE SEEN ON WATER VAPOR IMAGERY OVER UTAH/COLORADO WILL
LIFT THROUGH THE UPPER MIDWEST ON FRIDAY NIGHT AND INTO ONTARIO ON
SATURDAY. WITH THIS FEATURE PASSING NORTH OF UPPER MICHIGAN IT ONLY
SUPRESSES 500MB HEIGHTS TO BETWEEN 586-589DM ON SATURDAY. GIVEN THE
WEAK UPPER LEVEL FORCING...PREFERENCE IS TOWARDS THE SLOWER FRONTAL
TIMING GIVEN BY THE 12Z NAM/UKMET/ECMWF. THIS PLACES THE FRONT NEAR
OR SOUTH OF THE I-69 CORRIDOR BY THE MID-AFTERNOON/PEAK HEATING TIME
FRAME. LOCATIONS SOUTH OF THE FRONT WILL LIKELY STILL BE SOMEWHAT
CAPPED LEAVING SOME UNCERTAINTY IN CONVECTIVE POTENTIAL.
HOWEVER...WITH A WEAK FRONT IN THE VICINITY(POSSIBLY RECEIVING A
BOOST FROM LAKE BREEZES OFF LAKE HURON)...PUSHING SOUTH INTO THE
INCREASINGLY UNSTABLE AIRMASS(92/72 PARCEL) MAKES SEVERE WEATHER A
CONCERN ON SATURDAY AFTERNOON/EVENING. WHAT WE MAY LACK IN SHEAR
AND LARGER SCALE FORCING...WE WILL BE ABLE TO COMPENSATE FOR GIVEN
THE HIGH INSTABILITY...PROVIDING A THREAT FOR SEVERE STORMS WITH
STRONG WINDS BEING THE PRIAMRY THREAT. DEPENDING ON FRONTAL TIMING
A HEAT ADVISORY MAY ALSO NEED TO BE CONSIDERED GIVEN HEAT INDICIES
IN THE UPPER 90S TO NEAR 100 FOR THE GREATER DETROIT AREA AND
LOCATIONS FURTHER SOUTH.

davefootball123
07-01-2011, 12:46 AM
SREF and NAM are starting to come into decent agreement with the passage of the front. They both agree that we will be very unstable...Looks like some good dynamics are setting up. I think saturday could be interesting. Only thing that still isnt looking great is shear along and ahead of the coldfront.

Raedwulf
07-01-2011, 04:23 AM
YEA BABY!! Saturday is back on track!!! SLGT risk covering all of southern ontario

"THIS WILL LIKELY LEAD TO
SIGNIFICANT DESTABILIZATION/POTENTIAL INSTABILITY WITH SBCAPE
PERHAPS AS HIGH AS 4000-5000 J/KG SATURDAY AFTERNOON/EARLY EVENING."

StormJunkie
07-03-2011, 12:34 AM
Was on a two day holiday on Lake st. Claire and didn't check the models before heading out. As we were packing up this afternoon, I recognized the edges of (Cb) clouds on the horizon. By the time I got to Chatham, I was witnessing a very large cell moving SSE with another cell forming to its NW. I set up my camera and spent the next half hour recording it's progress until it hit Chatham right on. then for two hours, traveled home to Cambridge video taping the back end of the squall line. Got some great footage that I will have to edit and upload.

Over all, this was a mean storm system. Just watching the wind shear churning the clouds under the rain free base threw my head for a spin. Later on, the lightning made a spectacular appearance as I was heading back. Was a magnificent show that I will not forget.

Smokin Joe
07-03-2011, 07:38 AM
I chased the same storm and ended up in Forest as the leading edge came ashore from huron. It approached quite quickly and the gust front dropped the temp what seemed like 10 degrees or more instantly. There were branches pdown and a whole tree down on a sideroad north of town. Wind gusts were around 100km. Followed the line south and east right in the middle of the precip and then back across the 401 through some smaller and weakening cells that put on a really good lightshow and made it back to Bradford in time to see the front pass. Was in storms from 7-1030pm makes up for the dry spell lately with he storms. The rain free base was scary looking for sure on this storm it turned quite black prior to hitting. Great day for sure. Can't upload thumbnails from my iPhone now to the site I'm not sure why I have some pics of the storm as it overtakes the town. Darksky it says contact admi istrator if problem persists is there anything I can try to upload these pics from tapatalk?

obwan
07-03-2011, 08:17 AM
Buffalo explains why we here in Niagara stayed dry;

LAST NIGHT WAS CHARACTERIZED BY
CONVECTIVE FAILURE FOR MOST OF THE CWA. AN EXPANSIVE OUTFLOW
BOUNDARY FROM AN EARLIER UPSTREAM MCS PUSHED ACROSS MUCH OF WESTERN
NY AND REMOVED SOME INSTABILITY...BUT MORE IMPORTANTLY THE MID LEVEL
OUTFLOW FROM THAT MCS HAS DISRUPTED WHAT LITTLE CONVERGENCE THERE
WAS ALONG THE COLD FRONTAL BOUNDARY. WITH DISORGANIZED FLOW ALONG
THE LOW/MID LEVEL COLD FRONT THERE JUST IS NOT ENOUGH MOISTURE
CONVERGENCE TO GENERATE OR SUPPORT ANY DEEP MOIST CONVECTION.



I did get some lightning strikes over the lake, will try to post later.

DarkSky
07-03-2011, 12:30 PM
Great lightning show here in St. Kitts as the storm passed just out over the lake, but my line of site from the house was blocked by trees/houses, but I could see intense flashing occurring behind them. If I wasn't near-ready for bed I would have gone out to in good positioning to shoot it. Shot some stuff from inside the house (pictures posted in my lightning thread). Great LP storm (no precip here) too.

It would have been great to go shoot it over the lake, but I feel a bit uncomfortable in an open field at the top of a hill overlooking the lake standing next to an aluminum tripod while a lightning storm is going on...

DarkSky
07-03-2011, 12:59 PM
Summary from last night (Saturday, Jul.2) :

AWCN11 CWTO 031557
Weather summary for all of Southern Ontario and the
National Capital Region issued by Environment Canada
At 11:56 AM EDT Sunday 3 July 2011.

-------------------------------------------------------------
==weather event discussion==

An active 2nd of July...

A complex of thunderstorms rumbled along a warm front during the
morning giving very heavy downpours and frequent lightning across
Southwestern Ontario. Hail was reported by a Canwarn trained
Spotter in the forest city of London.

In the wake of the morning thunderstorms hot and humid air arrived
with temperature soaring to the mid thirties over the extreme
southwest. This set the stage for a cold front to trigger another
round of strong to severe thunderstorms across Southern Ontario.
While there was some tree damage in the Fergus area Saturday
Evening, most of the damage reports, mainly from Canwarn
Spotters, was in Essex County. Many areas received torrential
downpours reducing visibility to under 1 km, gusty winds, and a
Vivid lightning show put on by mother nature.

Numerous watches and warnings that were issued by environment
Canada have since been ended.

Severe weather reports received by Environment Canada as of 10.00
AM are in the table below.

-------------------------------------------------------------
Time(lcl) location event description

9.00 AM London 2-3 cm hail


7.50 PM Sarnia trees and power lines down

8.15-8.30 PM Windsor arpt 89 km/h squall gusting 109 km/h

8.50 PM 5 km E Fergus trees down

9.04-9,30 PM Windsor arpt wind gusts to 94 km/h
43 mm rain

9.00-9.30 PM Windsor trees and power lines down
3 cm size hail possibly larger
Building damage - siding ripped away

9.25 PM just N 2-3 cm hail
Leamington


This weather summary contains preliminary information
And may not constitute an official or final report.

END/OSPC