Unusual tropical storm-like low forms off coast of France
An unusual hybrid low pressure system has formed in the Mediterranean Sea, about 100 miles south of the coast of France. The low began as an extratropical storm named "Rolf", but has stalled out over the relatively warm waters of the Mediterranean over the past two days, and has acquired tropical characteristics. Heavy thunderstorms have built over the northeast portion of the low, and the storm has a symmetric spiral shape with a cloud-free center, like a tropical storm. The Navy is calling this system Invest 99L. The National Hurricane Center is not responsible for the Mediterranean Sea, so they are not issuing any products for 99L. NOAA's Satellite and Information Service (NESDIS) is giving 99L a tropical classification based on its satellite presentation, with winds in the 40 - 45 mph range. French radar shows heavy rains from 99L are beginning to affect Southeast France and the island of Corsica. The Lion Buoy, located about 100 miles to the west of the center of 99L, recorded sustained winds of tropical storm force, 40 mph, at 00 UTC yesterday. Water temperatures at the buoy were 17°C (63°F), far below the 26°C threshold usually needed to sustain a tropical storm. The coldest waters I've seen a tropical storm form in were 22°C during Hurricane Epsilon of 2005. I doubt that NHC would name this system if they did have responsibility for the Mediterranean, due to the cold water temperatures.
"Rolf" is expected to move slowly northwards into the coast of South France by Wednesday night. Meteo France is predicting heavy rains of 30 - 40 mm/hr (1.2 - 1.6"/hr) will affect the coast Tuesday night through Wednesday, with sustained winds of 50 mph, gusting to 75 mph.
Onzin...
1) NOAA geeft standaard ook namen aan subtropische stormen
2) Zeewatertemperaturen bedragen 20 graden in dit gebied. Grace en Vince come to mind...
3) NOAA was diegene die dit als een tropisch systeem heeft geclassificeerd
4) SST's van 26 graden zijn echt niet de heilige graal... Lapse rate is veel belangrijker. Als het op 500 Hpa -20 is, lukt het zeker wel om bij 20 graden SST tropische cyclogenesis te bewerkstelligen...
Misschien is het voor de heren en dames meteorologen eens tijd om net als de astronomen eens om tafel te gaan en met een duidelijke definitie te komen wat een tropische storm, en wat een polar low is. Ikzelf zou ongeveer 15 graden SST aanhouden, deze temperatuur houdt "polar lows" uit de (sub)tropische zeeen, en "tropische stormen" uit de (sub)arctische zeeen. Maakt het wel zo helder voor het grote publiek.
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