Monday, September 24, 2012

The Wandering Nadine

Nadine had straddled the line between tropical and nontropical entities for a while over the weekend, losing a chunk of thunderstorm activity near its center of circulation and "transitioning" to a nontropical storm system for a while on Saturday before developing additional thunderstorm activity and "reacquiring" a tropical designation. It's been a neat storm to watch as it spins and meanders slowly across the Eastern Atlantic, closer to Africa and Europe than to us in the US.

Nadine has straddled that subtropical/nontropical/tropical fence for a couple of days while spinning from near the Azores islands late last week to a position to the south of the Azores (and west-northwest of the Canary Islands, which are off of the Northwest Africa coastline), proving the "fun" in subjective classification of tropical cyclones.  While for our interests stateside it's not really an important matter (Nadine won't hit us), Nadine's weird path and life do provide a fair bit of scientific curiosity over the subjective nature of tropical versus nontropical entities as the storm has evolved over the past two weeks.

Nadine missed being picked up by a storm system to its north late last week and was forced southward by a developing high pressure ridge in the North Atlantic.  This allowed Nadine to move over warmer waters and develop a bit more thunderstorm activity near its low pressure center.   While Nadine spins slowly over the Eastern Atlantic, the current thinking from computer modeling is to take the storm slowly west and then northwest over the next several days.  Most models take the storm around the Azores a second time...

...with the exception being the Euro, which keeps the cyclone spinning across the Atlantic for the next ten days.  By a week from Wednesday, the computer model has Nadine positioned west of the Azores as a distinct storm system, sandwiched between a high to the northeast of the Azores and a trough to its west.

In terms of longevity, Nadine has a ways to go to reach the record for longest duration of tropical cyclones in the Atlantic. Overall, the record belongs to the 1899 San Ciriaco Hurricane at 28 days.  In the satellite era, Ginger from 1971 has the record at 27 plus days.  Kyle in 2002 was the last storm to seriously threaten the longevity marks, traversing the Atlantic for 22 days in a weird, snake-like path through the Central Atlantic before making US landfall towards the end of its life as a weak tropical storm.  Nadine still has a ways to go before even approaching these longevity records, and even if it is still around in ten day's time in some fashion it will not be the longest lasting cyclone in the would still have four or so days to go.

Nonetheless, it's a curious and tenacious storm to watch.