July 2, 2015: Salisbury’s Straight-Line Wind Event
The storm system that pushed through Salisbury yesterday left damage across parts of Wicomico county, leaving residents stunned thinking a tornado pushed through their neighborhood.
The National Weather Service (NWS) in Wakefield, VA forecasts for the Salisbury area and issues warnings when needed. The NWS did not send an actual survey team to the site of the damage, but they worked closely with Wicomico county officials and reviewed photos and videos. After the process, it was determined that the damage was caused by straight-line winds within a wet microburst.
A wet microburst, also called a “downburst” is a burst of fast flowing air that rushes out of a thunderstorm, colliding with the ground creating an outward movement of strong and dangerous winds. These systems can sometimes cause more damage than a weak tornado, but tornado damage and debris all have a swirl to it unlike microbursts. Microbursts also occur over a small area, typically less than a few square miles. In the image above, you can see a bit of a hook on the radar image at the time it pushed through Salisbury. This is sometimes an indicator of a strong storm with some rotation involved. The image below is an illustration showing the formation of microbursts.
Now that we know the cause of the damage, the next question is, why wasn’t there any warning from the NWS? I spoke with Mike Montefusco this morning, a forecaster at the NWS office in Wakefield. He said the wind speeds associated with the microburst in Salisbury were between 45-55 mph, which is below severe criteria. For a warning to be issued, winds must exceed 60 mph. The NWS was tracking the storm at the time and according to them, it did not appear to be severe. Montefusco said, “it certainly didn’t look severe on radar…winds were sub 40 knots or so…and no circulation signatures.” Here’s their findings below:
AFTER COLLABORATION WITH COUNTY EMERGENCY MANAGEMENT…WET MICROBURST WAS DETERMINED TO HAVE DOWNED SEVERAL TREES FROM MARBLE COURT TO KAYWOOD DRIVE… INCLUDING THE TIDE MILL APARTMENT COMPLEX. ALL DAMAGE WAS REPORTED IS IN A NARROW… 1 MILE STRETCH JUST NW OF SALISBURY AIRPORT…OR ALONG THE US-13 BYPASS. WIND SPEEDS IN THE AREA DURING THE EVENT WERE ESTIMATED TO RANGE BETWEEN 45 AND 55 MPH.
