Azores storm could become Subtropical Storm Alberto
An interesting and surprising hybrid low pressure system with both tropical and extratropical characteristics has formed over the far Eastern Atlantic, about 400 miles southwest of the southern Azores Islands. This low, designated Invest 92L by NHC today, has developed an impressive amount of heavy thunderstorm activity near its center, despite the fact that it is over cold ocean waters with temperatures of 66°F (19°C.) This is well below the 26°C usually needed for a tropical storm to form. However, there is quite cold air aloft, so the temperature difference between the surface the upper levels has been great enough to create sufficient instability for 92L to organize. Wind shear is a moderate 15 - 20 knots, and satellite estimates of 92L's winds were 63 mph at 1:45 pm EDT Saturday, according to NOAA/NESDIS. NHC estimated that 92L had top winds of 50 mph at 2 pm EDT Saturday.
Figure 1. Afternoon satellite photo of Invest 92L, taken at 16 UTC May 12, 2012, by NASA's Aqua satellite. Image credit: NASA.
NHC is giving 92L a 40% chance of developing into a named storm by Monday. They will be reluctant to name it Alberto unless the storm can maintain it's current level of heavy thunderstorm activity for at least 6 - 12 hours. The storm's heavy thunderstorms have weakened some during the afternoon, making it less likely NHC will be inclined to name it; the fact that 92L is over waters of 66°F (19°C) hurts its chances. The coldest waters I've seen a tropical storm form in were 19°C, during Tropical Storm Grace of 2009. Grace holds the record for being the farthest northeast forming tropical cyclone in the Atlantic basin. Like 92L, Grace also formed near the Azores Islands, but in early October. The coldest waters I've seen a hurricane form in were 22°C, for Hurricane Epsilon of 2005. Latest guidance from the computer models show 92L meandering to the south of the Azores through Monday, then beginning a slow motion towards the northeast by Tuesday.
Jeff Masters
Reader Comments
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Like the use skunked! Lots of clouds here this morning so hopefully we can get some sun to get this atmosphere to destabilize.
Got over 4" last week which has really greened things up around here but all those rains barely put a dent in the low lake levels.
A LOW PRES...ANALYZED 1008 ON THE 0600 UTC SURFACE MAP IS
LOCATED NEAR 10.5N105.5W. THUNDERSTORM ACTIVITY HAS INCREASED
OVERNIGHT NEAR THE CENTER WITH THE STRONGEST CONVECTION IN A
BAND WITHIN AROUND 75 NM W SEMICIRCLE OF LOW CENTER. UPPER-LEVEL
WINDS APPEAR CONDUCIVE FOR SOME TROPICAL DEVELOPMENT. IF THIS
RECENT DEVELOPMENT TREND CONTINUES...THEN A TROPICAL DEPRESSION
COULD FORM LATER TODAY. THIS SYSTEM HAS A HIGH CHANCE OF
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES
SLOWLY NORTHWESTWARD OR WEST-NORTHWESTWARD.
Reason ya haven't got answers so far is cuz reading charts showing over 5days into the future is closer to reading tea leaves than forecasting. But since I'm the village idiot...
...talk is that the bothersome closed-low will be forming near the Yucatan around the 20th and formed around the 23rd. So figuring storm travel time from the Yucatan to the Keys, changing reservations is as likely to put you into the midst of a TropicalStorm as not.
Personally I'd rather have the worst weather at the end of a week's vacation than at the beginning. Better "Thank goodness we're leaving." after having a nice few days than arriving for "Is it gonna be like this for the rest of the entire trip?"
And there's the possibility that it wouldn't head to the Keys even if a TropicalCyclone were to form.
But as I said, and meant, I'm the village idiot. There's gotta be folks more qualified to give you advice.
Edited in: And I was correct about folks more qualified...
Dr.JeffMasters: The models have backed off on their predictions of a potential subtropical storm developing over the Western Caribbean or waters near Florida this weekend...
lots of cloud cover this morning.
that's about it.
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