• Tag Archives derecho
  • Mammatus and Derechos

    66  bar steep rise 29.68  0mph NW dew-point 64  Summer, muggy night

    Waxing Crescent of the Thunder Moon

    Another line of storms moved out of the north west, along I-94.  They hit us about 8 PM, the skies green like pale mashed peas.  Kate noticed some mammatus clouds and a lightning display in the east, already headed toward someone else.  There were tornado touchdowns, far away this time.  These storms are our tsunamis, our earthquakes, our hurricanes.

    They come here because of our location, our spot on the globe.  They usually spawn from cool arctic air meeting humid Gulf of Mexico air drawn up by circulating lows.  Their paths have a general line, north west to south east, but the specific spots along the way that experience damage varies wildly.  A couple of storms ago a tornado touched down south of us about 2 miles.  A couple of years ago a tornado hit an eastern part of Andover.  That may have been the storm which hit us with hail, requiring new siding and a new roof.

    If a tornado hits your house, it may as well have been a tsunami, a hurricane or an earthquake.  The damage will be considerable, your life in danger.  Straight line winds generated by wall clouds can and do reach ground speeds of 90 mph.  In the first four years after we bought this house we had two straight line winds that took out several large trees in our woods.

    In certain instances these are derechos. The bow-shaped echoes that get meteorologists excited are distinguishing characteristics.  So are sustained straight lines above 58 mph, over a long front.  These are mostly a North American storm.