July 8, 2014 Severe Weather


Storm Summary

A significant outbreak of severe weather occurred across western and central New York on Tuesday July 8th, 2014. The region was square within the warm sector of a surface low pressure system shifting north of the Lower Great Lakes where warm and humid air created a very unstable environment as an upper level trough of cold air moved overhead. Large scale lift provided by a shortwave trough embedded within a 60-80 knot jet stream aloft and a surface cold front to the west helped severe thunderstorms to develop across Ohio and Pennsylvania near midday. These storms moved across western then central New York state through the afternoon and evening where strong wind shear and the presence of a Mesoscale Convective Vortex (MCV) helped the storms produce long swaths of damaging winds from the western Southern Tier to just south of Rochester then southeast and east of Lake Ontario. Over 70 severe weather reports were received for downed trees and power lines as well as significant property damage. A single short lived but damaging tornado was also surveyed across Lewis county, NY. (See Storm Reports section below for more detailed reports of storm damage.)

WPC surface analysis from 2PM EDT. Low pressure is centered near Georgian Bay with a cold front across northwest Ohio and warm front well north of Lake Ontario. This places NY in the warm sector of the Low pressure system which is a favorable environment for severe weather development.
Water vapor satellite imagery from 140PM EDT with 500 millibar height contours. A strong embedded shortwave trough annotated by the dashed red line was shifting east across Ohio. This feature was the large scale trigger for storms forming over eastern OH (yellow circle) which would eventually move across NY.
SPC Mesoscale Analysis from 4PM EDT showing contoured Most Unstable CAPE and a very impressive 50-70 knots of Effective Bulk Shear. CAPE is a measure of instability where values of 1000 - 2000 J/kg are sufficient for strong to severe storms while the Effective Bulk Shear is a measure of winds throughout the bottom half of a storm environment. Only 25-40 knots are needed for Supercells.


Mesoscale Discussion issued by the Storm Prediction Center at 1129AM EDT. Contours of Mixed Layer CAPE, 0-6 Km Wind Shear and 500 millibar temperatures displayed. This product highlighted a 80% probability of issuance of a Severe Thunderstorm Watch as ingredients for severe storms including moisture, lift, instability and wind shear were coming together over Ohio, Pennsylvania and New York. SPC convective outlook from 1230PM EDT. An earlier Slight Risk across upstate NY was upgraded with a portion of western and central New York included in a Moderate Risk for severe weather while the rest of Upstate NY remained in a Slight Risk for severe weather including risks for damaging winds, large hail and isolated tornadoes.
Severe Thunderstorm Watch issued by the Storm Prediction Center at 105PM EDT with primary threats being widespread damaging winds, isolated large hail and a tornado or two.


Radar Reflectivity Loop

Loop of half-hour interval Buffalo (KBUF) and Montague (KTYX) radar 0.5 degree reflectivity images from 1PM to 730PM EDT showing the severe thunderstorms that developed along the MCV as it swept across New York. Also overlaid are cloud-to-ground lightning strikes and warning polygons. Notice the red colors which show the most intense storm cores.

Radar Radial Velocity Loop

Loop of half-hour interval KBUF and KTYX radar 0.5 degree radial velocity images from 1PM to 730PM EDT showing the radar detected wind speeds of rain and hail within the thunderstorms as they swept across New York. The green/blue colors are radial velocity moving toward the radar and the red/orange colors are radial velocities moving away from the radars. The brighter red/orange or green/blue indicates strong winds within the thunderstorms. These strong winds were brought down to the surface by the storms producing the reports of widespread wind damage. The first 10 images are radial velocity from KBUF then as the strong winds moved east the last 4 images are taken from KTYX.

Oswego County Damaging Straight Line Winds

Significant straight line wind damage was observed in Oswego county from a thunderstorm cluster which showed a radar reflectivity pattern of a bow echo with rear inflow notch and radial velocity pattern of winds over 80kts or near 100mph. The left image is the radar reflectivity from KTYX at 602PM EDT. Note the bowing line annotated with the black curved line and the black arrows showing the direction of movement. This pattern indicates strong winds within the line of thunderstorms. The left most arrow on this image points toward the rear inflow notch where radar reflectivities are reduced do to the strong winds rushing into the back of the line of storms. The right image shows radial velocity returns of over 80kts within the annotated black circle. When winds of this magnitude reach the ground they can bring significant damage along the storm's path. The damage pattern from straight line winds shows damage all blown toward the direction the storm was moving.

Lewis County Tornado

This image shows radar radial velocity from the Montague, NY Doppler Radar (KTYX) at 0.5 degrees above the ground with a timestamp of 6:52PM EDT. Red colors indicate radial velocity going away from the radar and green represents radial velocity toward the radar. Annotated on the image is approximately the track of the EF-1 rated tornado (light blue) with yellow arrows showing a broad inbound (toward the radar) next to outbound (away from the radar) radial velocity couplet indicating broad rotation inside the storm. At this time step a single maximum 90 knot outbound radial velocity pixel along the surveyed tornado track is shown. Tornadoes which occur within the type of environment similar to what was in place this day typically only touchdown for a few short minutes and have very small radial velocity couplets. Significant damage was found along the path of this tornado with more details found in the Public Information Statement issued after the storm survey was complete.

Storm Reports


Disclaimer

Click on the image to navigate to a web page where you can zoom and scroll the map and click on the individual storm reports for more information.


Storm Survey Photos of Damage in Lewis County