Thursday, July 24, 2014

Warm Season Storms

The Mid-Atlantic is often in the crosshairs of major weather events that barrel down from arctic or rumble up from the tropics. We live precisely in the region where cold air masses from the north collide with warm air masses from the south, and where ocean systems come ashore to land in our backyards. I can't remember a time when I didn't thrill to having a front row seat to these dramatic events, and though some were dangerous and one or two (maybe more) scared the wits out of me, I  love the excitement of tracking summer systems and learning the why's and how's of extreme weather. Hiking, paddling, driving, and walking through the summer, I am always on the lookout for evidence of how warm season storm events such as tornadoes, micro-bursts, front line winds, thunderstorms, and hurricanes, change our landscape.

Granddaughter Kenzey and I chased this big thunderstorm to the grocery store - shelf or Arcus cloud at base.

Arcus cloud over Swan Harbor Farm dropping cool sinking air into surrounding warm air mass below the main storm.

Evidence of past storms is all around us, we only need to learn how to read the landscape for the story.  Hiking through Eastern forests, we can see a strange  surface topography called 'pillow and cradle' that has nothing to do with human activity. The mounds are the remnants of wind-thrown trees at the root mass, long decayed, leaving a great pile of soil and embedded cobbles. The hole from where the tree was ripped from the soil lays at the base of the mound. Large collections of mound and cradle topography can be traced to strong summer storms, micro-bursts, or in some Northeast forests that have never been harvested - great historic storms like the Hurricane of 1938. 

Pillow and cradle surface topography in a Northeast forest.

On a recent visit to Sagamore Hill National Historic Site, the family home of Teddy Roosevelt in Oyster Bay, NY, my nine-year-old granddaughter couldn't help but 'whoa!' all the way to the water's edge at the sight of dozens of massive trees cut from the trail. We counted rings on stumps and observed openings where large patches of raspberries (that we ate) growing in a recent canopy openings. This was evidence of Hurricane Sandy that only two years ago tore through the Mid-Atlantic in October 2012. This was a scary storm for those of us who lived near the Mason-Dixon Line as the eye passed right along the boundary of Maryland and Pennsylvania, and pummeled us with northern trailing edge winds. It left us without power for ten days - and plenty of raspberries this summer!

Sagamore Hill NHS at Oyster Bay, NY, bears scars of Hurricane Sandy, 2012.

The boardwalk to the cobble and shell beach at Sagamore Hill had been replaced in 2013, the old one torn out by the storm. Much of the brackish grass meadow was killed by saltwater overwash.  Ragged gaps in the forest edge revealed that many of the old trees had been blown down and tidal guts and ponds now stood where entire patches of forest were ripped away.  Nature will soon fill the gaps and reorganize new ecological communities in these raw areas.

Raw, open gashes in the bay forests at Sagamore Hill NHS.

Citing a shortage of lumber as a reason for the delay in rebuilding the ruined boardwalk, the NPS used plastic wood product instead. It will be interesting to see how this material holds up in the next big storm to come this way.

Photo: National Park Service

High heat and humidity clashing with cool air masses create our most impressive storms along the Chesapeake Bay. Super cells can top out at 70,000 feet and rotate at their bases like slow-motion tornadoes or very small hurricanes. The precipitation from these monster storms can come as deluges, dropping several inches of rain over an hour.  Highly charged, a super cell can fill the air with weak but noticeable static electricity until dramatic bolts of cloud-to-cloud or cloud-to-ground lightening releases energy that can cause quite a disruption in our daily lives.

This huge summer storm sent a bolt of lightening that blew out our computers, lights, and set off alarms at Swan Harbor.

A rapidly building super cell over Swan Harbor Farm.

Unlike the West, lightening strikes here in the East do very little damage to our forests as the region is less prone to arid, droughty conditions. But that is not to say we don't have our fair share of ground strikes. Hikers who take to the forests in summer season are cautioned to be wary of hiking along ridgelines and promitories when thunderstorms approach. I've been in two very close calls on days that started out beautiful and ended in powerful storms that wreaked havoc with high winds, frequent lightening, and tremendous rains that resulted in dangerous flooding.

Lightening-struck tree in Elk Neck State Park, right on the MDT.
As many of us are hiking, biking, paddling, and exploring the out-of-doors during the warm months July through October, it's good to be storm-aware and know how to take precautions against rapidly building or moving storms. Once we learn the how's and why's we can better appreciate the awe and excitement of storm watching - and even a little chasing!

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