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The following is the EC summary of weather events over the stormy past weekend of Friday, July 19, 2013 and Saturday, July 20, 2013. EWR adds some of our graphics and info from our own monitoring activities below the summary.

Environment Canada Summary:

Updated weather summary for all of Southern Ontario and the
National Capital Region issued by Environment Canada
At 10:46 AM EDT Monday 22 July 2013.

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

A hot and humid air mass ahead of a cold front provided the perfect
combination to set off severe thunderstorm activity across Central
and Southern Ontario Friday. The severe weather became extensive
during the afternoon and evening hours resulting in the biggest
severe weather outbreak of the season. An exceptionally large area
was affected, from Windsor to Ottawa and from Lake Erie to North Bay.

Friday morning, thunderstorms gave severe wind damage to callander
(near North Bay) resulting in the declaration of a state of emergency
for the town.

Severe thunderstorms continued to develop eastward and southward. In
the early afternoon, storms produced a swath of damage from Pembroke
to Petawawa where cars were flipped over, roofs blown down, trees
uprooted, street lights snapped, and trailers overturned. By late
afternoon, wind damage was reported in dozens of communities in a
broad swath from Lake Huron and Georgian Bay through to Eastern
Ontario.

The severe storms developed southward during the evening hours,
causing wind damage in the Golden Horseshoe and in Southwestern
Ontario. Flooding and downed trees were reported in Niagara Falls
with rainfall estimated at 75 to 100 mm. 150 mm was reported to have
fallen at Rondeau bay.

2 minor injuries were reported in Chatham late Friday evening when a tree fell on a car with the people in it.

Hundreds of thousands of residents were left without power following the storms. As of this morning, approximately 17,000 homes remained
without power.

Environment Canada storm damage teams have investigated damage in
Barrie, Orillia, Gravenhurst, Hamilton, Petawawa, callander and
Dufferin County. The most severe damage was found near honeywood, in
duffern county, where estimated winds of 150 km/hr destroyed a cattle
barn and threw the roof 300 metres. This damage rates ef1 on the
enhanced Fujita scale. Evidence thus far indicates that the storm
damage in Ontario was caused by straight-line, downburst winds.

Below is a list of the most significant damage reports that
Environment Canada has received as of 7:00 PM Sunday.

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

11:20 AM Gravenhurst 2.5 cm hail

12:40 PM Petawawa and roof damage, trailers flipped,
Pembrooke power outages

12:55 PM Petawawa plaza front facet off, windows blown out,
Roof caved in

1:55 PM Gravenhurst large trees down, power lines down

2:30 PM Coldwater trees down and snapped, power outages

2:45 PM Gravenhurst cars overturned

2:50 PM Orillia trees down, power lines down, street
Lights snapped

2:55 PM lake dalrymple power lines and trees down

3:00 PM W of Ottawa roof damage, crop damage, trees down

3:00 PM’s of Gull Lake 150 trees down on South Morris island

3:15 PM Barrie funnel cloud, trees down – caused
Damage to homes

3:20 PM se of tree damage
Bracebridge

3:20 PM Bobcaygeon trees uprooted

3:30 PM Kanata large hail

4:00 PM N of Arthur trees down

4:35 PM Barrie building damage, trees snapped,
Power outages

4:50 PM Listowel wind gust of 92 km/h

5:10 PM Ottawa trees down (primarily in west end)

5:10 PM Borden wind gust of 96 km/h

5:10 PM mulmar barn roof thrown 300 metres, barn
Destoyed near honeywood, ef1 damage,
Winds estimated at 150 km/hr.

5:15 PM Napanee trees down, gas leaks, power outages

5:30 PM Innisfil funnel cloud, limbs down

5:30 PM Waterloo arpt wind gust of 119 km/h, trees down

5:35 PM sw of Bradford funnel cloud

5:40 PM Guelph dozens of trees snapped or uprooted,
Hundreds of branches down, damage to
Homes from fallen trees or limbs

5:45 PM Casselman 53 mm rain

5:50 PM Kitchener trees down – caused damage to homes,
-Waterloo power outages, damage to bus shelter

5:50 PM Stratford trees down

5:55 PM Port Carling mature trees down, trees snapped
Port Severn

5:55 PM Gravenhurst large trees down, power lines down

6:00 PM Toronto Pearson wind gust of 104 km/h

6:00 PM paris tree damage, wooden balcony torn off
House, cinderblock warehouse collapse

6:10 PM Toronto trees down, including a
Historic century old tree, power
Lines down

6:30 PM Hamilton trees down

6:45 PM Stoney Creek trees down, trees snapped

7:05 PM Hamilton arpt wind gust of 104 km/h

7:10 PM St Catharines trees down, 75-85 mm of rain,
Flooding

7:3o PM Chatham trees down, power lines down,

7:45 PM Grimsby trees down, power outages, 65 mm of
Rain

7:45 PM Waterdown trees down

8:20 PM Chatham-Kent trees down, power outages

8:30 PM Ancaster trees and power lines down, small
Hail

8:45 PM norwich wind gust of 90 km/h, trees down

9:00 PM mulmur barn damage, crop damage, roof
Damage, power outages

9:10 PM Hamilton arpt wind gust of 106 km/h

9:20 PM Mount Hope trees down, trampoline blown onto
Roof, crop damage

10:00 PM Port Colborne wind gust of 98 km/h

11:00 PM Port Colborne wind gust of 93 km/h, power outages

02:00 AM (sat) Waterloo arpt wind gust of 91 km/h

Reports with exact time unknown:

St George trees and hydro lines down
Essex County trees down
Simcoe County trees down
Rondeau bay 150 mm rain
Chatham minor injuries to two passengers of
A car
Wiarton large tree uprooted
Blenheim trees down, flooded basements, power
Outages
Niagara Falls 75-100 mm rain, flash flooding
Beamsville/ 75-85 mm rain, flash flooding
Vineland

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

Observations from EWR:

EWR’s rain gauge measured 35mm of rain by the completion of the frontal passage Saturday morning. In the radar animation below, covering the time from 7:28 pm Friday to 9:01 am Saturday morning, two storm systems collided over the Niagara Escarpment at Grimsby at approximately 9:10PM Friday evening (early part of the animation). The westernmost system advanced eastward along the north shore of Lake Erie from the St. Thomas area, and colliding with the system moving southerly across the GH-GTA from the Kitchener-Waterloo area. The Lake Erie system was strongly electified, and the light show was impressive. The gust front from that system was strong with torrential rain in wind as it passed over Dundas, Ancaster and Hamilton. The bulk of the rain we measured at EWR came from that gust front.

20130720 Click image to start animation if it doesn’t start on its own.

[click on any of the following images to see them full size]

2013-0719-srv1-619

This Storm Relative Velocity* image, taken at 6:20pm on Friday, shows two areas of rotational development along the gust front of the storm line that had just arrived from the Kit-Wat area. The inverted pink triangle is a “TVS signature” sent out by the KBUF radar system, indicating conditions for tornadic rotation exist. Immediately to the right of the TVS signature is a very tight “couplet” – bright red and green, indicating that rotational winds exist. The beam centre at this distance from the Buffalo station is about 4300 feet, so it is unknown if this rotation yielded a waterspout or not (its over Lake Ontario at this point).

South of Cobourg, another area of suspected rotational development – quite a large area, suggesting the storm cell is developing a rotating core. The bright green is suggestive of a strong in-flow jet.

When this storm passed over Dundas, there was a strong “fresh earth” smell to the storm leading edge, and a bit of “greenness” to the advancing shelf. Both are suggestive that there had been tornadic activity in the cell in its travels, or at least very strong updraft over open land.

* Storm Relative Velocity – a radar measure of the direction and intensity of winds in a storm, relative to the wind velocity over ground of the storm. Visualizes the wind within a storm, as opposed to the wind we feel over ground. Green – winds flowing toward the radar station, red, flowing away. To be tornadic the couplet must straddle a radial – a line drawn from the radar site to a couplet.

2013-0719-srv2619-2

This image is a zoom-in of the previous one, to get a better look at the couplet. Key elements are the tight and intense colour change. This is indicative of very tight rotation, consistent with a small but well defined funnel, tornado or waterspout.

2013-0719-srv3637--1

A combined Storm Relative Velocity (right) and Base Reflectivity view of the previous area, approximately 20 minutes later. The storm line has moved further across the lake. The previous couplet has dissipated, and a new TVS has come up, although there isn’t any overt indication in the SRV pattern to indicate a cell. These views only represent one angle sweep – the lowest tilt – there may have been more evidence in higher tilts.

The Coboug pattern is better defined and is most likely a strong inflow jet. This is borne out by the shape of the cell in the Base Reflectivity scan. This is a tornadic supercell in the making, but it didn’t mature much beyond this phase.

Of interest, is the well defined “gust front” shelf or roll cloud formed ahead of the storm over Niagara. Notice the thin cloud line in the base reflectivity scan, and the thin green and red line in the SRV scan, stretching from Youngstown in a gentle arc eastward out of the frame, just ahead of the main cloud mass.

2013-0719-srv5638-1

This image is the same as the previous scan, just one radar cycle later. The TVS icon has dropped, but the Cobourg cell is maintaining its integrity.

2013-07-11: Tropical Storm Chantal has dissipated.

2013-07-10: Tropical Storm Chantal is having difficult holding together and may diminish to a tropical wave.

The images above contains active information elements which can be accessed at the NHC site. Click on the image to go there or to the National Hurricane Center.

WTNT33 KNHC 100837
TCPAT3

BULLETIN
TROPICAL STORM CHANTAL ADVISORY NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
500 AM AST WED JUL 10 2013

…CHANTAL WEAKENING…
…MAY BE DEGENERATING INTO A TROPICAL WAVE…

SUMMARY OF 500 AM AST…0900 UTC…INFORMATION
———————————————-
LOCATION…16.5N 69.5W
ABOUT 260 MI…420 KM WSW OF SAN JUAN PUERTO RICO
ABOUT 140 MI…225 KM S OF SANTO DOMINGO DOMINICAN REPUBLIC
MAXIMUM SUSTAINED WINDS…45 MPH…75 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 29 MPH…46 KM/H
MINIMUM CENTRAL PRESSURE…1011 MB…29.85 INCHES

WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY…

THE TROPICAL STORM WARNING FOR PUERTO RICO…AND THE TROPICAL STORM
WATCH FOR THE U.S. VIRGIN ISLANDS…VIEQUES…AND CULEBRA ARE
DISCONTINUED.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

A TROPICAL STORM WARNING IS IN EFFECT FOR…
* ENTIRE COAST OF THE DOMINICAN REPUBLIC
* ENTIRE COAST OF HAITI
* TURKS AND CAICOS
* SOUTHEASTERN BAHAMAS

A TROPICAL STORM WATCH IS IN EFFECT FOR…
* CENTRAL BAHAMAS

INTERESTS IN EASTERN CUBA AND THE NORTHWESTERN BAHAMAS SHOULD
MONITOR THE PROGRESS OF CHANTAL.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA…PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 500 AM AST…0900 UTC…THE CENTER OF TROPICAL STORM CHANTAL WAS
LOCATED NEAR LATITUDE 16.5 NORTH…LONGITUDE 69.5 WEST. CHANTAL IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 29 MPH…46 KM/H…AND THIS
GENERAL MOTION WITH A DECREASE IN FORWARD SPEED IS EXPECTED THROUGH
TONIGHT. A TURN TOWARD THE NORTHWEST IS EXPECTED ON THURSDAY…
FOLLOWED BY A TURN TOWARD THE NORTH-NORTHWEST ON THURSDAY NIGHT.
ON THE FORECAST TRACK…THE CENTER WILL BE NEAR OR OVER HISPANIOLA
LATER TODAY…NEAR OR OVER EASTERN CUBA BY EARLY THURSDAY…AND
NEAR CENTRAL CUBA BY LATE THURSDAY.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 45 MPH…75
KM/H…WITH HIGHER GUSTS. SOME WEAKENING IS FORECAST DURING THE
NEXT 48 HOURS. SATELLITE IMAGES…SURFACE OBSERVATIONS…AND AIR
FORCE HURRICANE HUNTER DATA INDICATE THAT CHANTAL HAS BECOME
DISORGANIZED…AND THE SYSTEM COULD DEGENERATE INTO A TROPICAL WAVE
LATER TODAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 90 MILES…150 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1011 MB…29.85 INCHES.

HAZARDS AFFECTING LAND
———————-
WIND…TROPICAL STORM CONDITIONS COULD REACH THE DOMINICAN REPUBLIC
LATER THIS MORNING…AND HAITI LATER TODAY. TROPICAL STORM
CONDITIONS COULD OCCUR OVER PORTIONS OF THE SOUTHEASTERN BAHAMAS
AND THE TURKS AND CAICOS TONIGHT…AND OVER PORTIONS OF THE CENTRAL
BAHAMAS BY EARLY THURSDAY.

STORM SURGE…A STORM SURGE…ACCOMPANIED BY DANGEROUS WAVES…WILL
RAISE WATER LEVELS BY AS MUCH AS 1 TO 2 FEET IN THE TROPICAL STORM
WARNING AREA.

RAINFALL…CHANTAL IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
3 TO 6 INCHES OVER PUERTO RICO…THE U.S. VIRGIN ISLANDS…THE
SOUTHEASTERN BAHAMAS…THE DOMINICAN REPUBLIC AND HAITI. ISOLATED
MAXIMUM AMOUNTS OF 10 INCHES ARE POSSIBLE OVER HISPANIOLA.

WTNT43 KNHC 100837
TCDAT3

TROPICAL STORM CHANTAL DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL AL032013
500 AM AST WED JUL 10 2013

OBSERVATIONS FROM A HURRICANE HUNTER MISSION AND NOAA DATA BUOY
42059 INDICATE THAT CHANTAL MAY NO LONGER HAVE A CLOSED
CIRCULATION. THE SATELLITE PRESENTATION OF THE SYSTEM HAS ALSO
DETERIORATED MARKEDLY THIS MORNING…AND IS BARELY CLASSIFIABLE BY
THE DVORAK TECHNIQUE. FLIGHT-LEVEL AND SFMR SURFACE WINDS DO NOT
SUPPORT AN INTENSITY OF MORE THAN 40 KT…AND THE CURRENT WIND
SPEED IS SET AT THAT VALUE. EVEN IF CHANTAL DOES NOT CEASE ITS
EXISTENCE AS A TROPICAL CYCLONE…DYNAMICAL GUIDANCE SHOWS STRONG
WESTERLY SHEAR OVER THE SYSTEM FOR THE NEXT COUPLE OF DAYS. THE
SHEAR…ALONG WITH LAND INTERACTION…SHOULD CAUSE FURTHER
WEAKENING. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE
STATISTICAL-DYNAMICAL LGEM GUIDANCE AND THE INTENSITY MODEL
CONSENSUS.

ALTHOUGH THE CENTER IS DIFFICULT TO TRACK…THE BEST ESTIMATE IS
THAT CHANTAL MOVED VERY RAPIDLY WESTWARD…NEAR 28 KT…OVER THE
PAST SEVERAL HOURS. A MORE CONSERVATIVE…LONGER-TERM…ESTIMATE
OF INITIAL MOTION IS 285/25. A WELL-DEFINED MID-LEVEL RIDGE TO THE
NORTH OF THE STORM HAS BEEN STEERING IT QUICKLY WESTWARD TO
WEST-NORTHWESTWARD. A WEAKNESS IN THE RIDGE IN THE VICINITY OF THE
EASTERN GULF OF MEXICO AND THE FLORIDA PENINSULA SHOULD RESULT IN
CHANTAL…OR ITS REMNANT…TURNING TOWARD THE NORTHWEST AND NORTH
OVER THE NEXT FEW DAYS. SINCE THE INITIAL POSITION HAS BEEN
SHIFTED SUBSTANTIALLY WESTWARD IN COMPARISON TO THE PREVIOUS
ADVISORY… THIS NECESSITATES A LARGE WESTWARD SHIFT TO THE NHC
FORECAST TRACK. NONETHELESS…THE NEW OFFICIAL FORECAST IS STILL
ON THE EASTERN SIDE OF THE TRACK MODEL GUIDANCE SUITE.

SINCE THE CYCLONE MAY BE OPENING UP INTO A WAVE…ADVISORIES MAY BE
DISCONTINUED LATER TODAY.

FORECAST POSITIONS AND MAX WINDS

INIT 10/0900Z 16.5N 69.5W 40 KT 45 MPH
12H 10/1800Z 17.8N 72.3W 35 KT 40 MPH
24H 11/0600Z 19.5N 75.7W 30 KT 35 MPH
36H 11/1800Z 21.5N 78.5W 30 KT 35 MPH…INLAND
48H 12/0600Z 23.8N 79.5W 30 KT 35 MPH
72H 13/0600Z 27.5N 80.0W 30 KT 35 MPH
96H 14/0600Z 31.0N 81.0W 35 KT 40 MPH
120H 15/0600Z 32.5N 82.0W 25 KT 30 MPH…INLAND

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