You are currently browsing the monthly archive for July 2011.
SEVERE WEATHER ALERT — 02:56 AM EDT Jul 29 2011
This is an automated alert of potentially severe weather for the Golden Horseshoe- Greater Toronto Area, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 02:56 AM EDT on Jul 29 2011, from radar data analyzed
from NWS radar site KBUF in Buffalo, NY, operating in Short Range Composite Reflectivity (NCR), VCP mode 212.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert
was equal to or greater than: 65 dbZ. These values are an indication of potentially severe weather within the alert scan zone:
*** “8” to 16″/hr very heavy rain: marble size to golf ball sized hail possible” ***
and may include extremely strong storm related winds and tornadic activity.
Go to http://radar.ephemerata.ca for current radar views of the alert zone and monitor official weather reports to assess your personal risk.
[Cross-posted from the EWR Blog]
Probably. Environment Canada will make the official determination, but the radar evidence from last night suggests a small strong F0 and perhaps a weak F1 one was quite likely. A compact but intense cell crossed into Southwestern Ontario east of Sarnia about 7PM in the evening July 23, 2011.
We watched the cell develop strong verticality over the next couple of hours with high hail densities evident high in the updraft. We noted an MDA event (“mesocyclone detection algorithm” – an automated detection of updraft rotation in a thunderstorm, converting it from an ordinary thunderstorm to a supercell) over this cell about an hour after it crossed the lake shore. The reflectivity radar trace indicated a large upper hail core.
The overall presentation of the cell didn’t suggest a classic tornadic mesocyclonic cell. However, when we looked at the storm relative velocity profile on the lowest tilt we found the couplet (yellow arrow) shown in fig. 1. The couplet didn’t show on further upward tilts, indicating some degree of rotation was occurring near or at the base of the cell. Since the distance between KDTX and the location of the couplet is about 80 miles, the SRV couplet indicated a velocity disturbance around 5000 feet. Since the beam is narrow, and above the ground, it cannot determine how low the disturbance went.
Figure 1. Storm Relative Velocity couplet, July 23, 2011, Lambton Co.
A velocity couplet in a storm relative velocity profile indicates a rapid change in the direction component of the velocity vector (velocity, by definition, is the combination of speed and its direction context). Storm relative velocity profiles measure changes within a wind profile, and therefore will show when there is a significant change in direction of wind, like occurs in a tight rotating air column).
Though the scale is not shown in fig. 1, the wind shift in the couplet can be measured. The light green portion of the couplet measures to -44 knots, to +15 knots for the immediately adjacent red bin. This translates to a wind shift (rotation) occuring at approximately 120 km/h. This measured amount puts the event at the high end of the F0 scale (64-116 km/h and the low end of the F1(117-180 km/h) range. The couplet doesn’t indicate whether or not any rotation actually reached the ground. Damage evaluation will confirm further if the duration was enough to consider a full fledged low power tornado. The SRV couplet survived on the radar scan for more than one cycle, indicating the event would possibly have been in play for several minutes.
SEVERE WEATHER ALERT — 08:04 PM EDT Jul 24 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 08:04 PM EDT on Jul 24 2011, from radar data analyzed
from NWS radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 60 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “4” to 8″/hr very heavy rain: marble size hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
SEVERE WEATHER ALERT — 07:27 PM EDT Jul 24 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 07:27 PM EDT on Jul 24 2011, from radar data analyzed
from NWS radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 65 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “8” to 16″/hr very heavy rain: marble size to golf ball sized hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
SEVERE WEATHER ALERT — 06:06 PM EDT Jul 24 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 06:06 PM EDT on Jul 24 2011, from radar data analyzed
from NWS radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 60 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “4” to 8″/hr very heavy rain: marble size hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
SEVERE WEATHER ALERT — 07:38 PM EDT Jul 23 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 07:38 PM EDT on Jul 23 2011, from radar data analyzed
from NWS radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 65 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “8” to 16″/hr very heavy rain: marble size to golf ball sized hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
UPDATE: Buffalo advises it’s back in service, although I note updates are a bit erratic.
NOUS61 KCLE 230419
FTMBUF
Message Date: Jul 23 2011 04:19:06
The Buffalo radar is down due to transmitter problems. Estimated time of return to service is unknown.
SEVERE WEATHER ALERT — 05:16 PM EDT Jul 18 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 05:16 PM EDT on Jul 18 2011, from radar data analyzed
from radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 60 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “4” to 8″/hr very heavy rain: marble size hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
SEVERE WEATHER ALERT — 05:04 PM EDT Jul 18 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 05:04 PM EDT on Jul 18 2011, from radar data analyzed
from radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was equal to or greater than: 60 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “4” to 8″/hr very heavy rain: marble size hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
SEVERE WEATHER ALERT — 04:52 PM EDT Jul 18 2011
This is an automated alert of potentially severe weather conditions for portions of western and southwestern Ontario, from Ephemerata Weather Radar. See attached scan image.
The alert triggered at 04:52 PM EDT on Jul 18 2011, from radar data analyzed
from radar site KDTX in Detroit, MI, operating in Short Range Composite Reflectivity (NCR), VCP mode 12.
This alert was issued because radar echo returns exceeding 60 dbZ have been detected in the alert zone. The maximum detected radar echo level in this alert was: 60 dbZ. These values are an indication of possible severe weather occuring or developing within the alert scan zone:
*** “4” to 8″/hr very heavy rain: marble size hail possible”
and may include extremely strong storm winds and tornadic activity. Go to
http://radar.ephemerata.ca for current radar views of the alert zones and monitor official weather reports to assess your personal risk.
EWR Wx ALERT 