Update, November 21, 2013, 9:43 a.m. Eastern: Tropical Storm Melissa – the loose cannon of the 2013 Atlantic hurricane season, racing over the ocean and remaining tropical over cool water, now threatening the Azores:
WTNT44 KNHC 210837
TROPICAL STORM MELISSA DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013
500 AM AST THU NOV 21 2013
EVEN THOUGH MELISSA IS CURRENTLY OVER QUITE COOL 21 C SEA SURFACE
TEMPERATURES…THE STORM IS STILL PRODUCING DEEP CONVECTION AND IS
HOLDING ON TO TROPICAL CYCLONE STATUS. THE MAIN REASONS THE STORM IS
ABLE TO REMAIN TROPICAL OVER THE COOL WATER IS BECAUSE OF THE
COMBINED FACTORS OF A COLD AIRMASS ALOFT AND FAIRLY LOW WIND SHEAR.
THE CLOUD PATTERN STILL CONSISTS OF FRAGMENTED CURVED BANDS MAINLY
CONFINED TO THE WESTERN PORTION OF THE CIRCULATION…AND THE DVORAK
CLASSIFICATIONS STILL SUPPORT AN INTENSITY OF 45 KT. MOST OF THE
MODELS SHOW MELISSA CHANGING LITTLE IN STRENGTH OVER THE NEXT
COUPLE OF DAYS…BUT THE SYSTEM WILL LIKELY BE LOSING ITS TROPICAL
CHARACTERISTICS DURING THE NEXT 12 TO 24 HOURS WHILE IT MOVES OVER
SEA SURFACE TEMPERATURES LOWER THAN 20 C. AFTER THE CYCLONE BECOMES
POST-TROPICAL…A GRADUAL WEAKENING IS PREDICTED WITH DISSIPATION
EXPECTED IN 3 TO 4 DAYS.
MELISSA CONTINUES TO RACE EAST-NORTHEASTWARD AT 28 KT EMBEDDED IN
THE STRONG MID-LATITUDE FLOW TO THE SOUTHEAST OF A LARGE
EXTRATROPICAL CYCLONE. A DECREASE IN FORWARD SPEED AND A TURN TO
THE EAST AND THEN SOUTHEAST ARE EXPECTED OVER THE NEXT FEW DAYS. THE
NHC FORECAST IS AGAIN ADJUSTED SOUTHWARD…FOLLOWING THE LATEST
TREND IN THE GUIDANCE.
GALE-FORCE WINDS ARE EXPECTED TO SPREAD ACROSS THE WESTERN AND
CENTRAL AZORES LATE TODAY OR TONIGHT AFTER MELISSA LOSES TROPICAL
FORECAST POSITIONS AND MAX WINDS
INIT 21/0900Z 39.1N 38.5W 45 KT 50 MPH
12H 21/1800Z 40.2N 33.6W 45 KT 50 MPH
24H 22/0600Z 41.5N 27.7W 45 KT 50 MPH…POST-TROPICAL
36H 22/1800Z 42.2N 22.8W 45 KT 50 MPH…POST-TROP/EXTRATROP
48H 23/0600Z 42.2N 19.8W 40 KT 45 MPH…POST-TROP/EXTRATROP
72H 24/0600Z 40.0N 16.5W 30 KT 35 MPH…POST-TROP/EXTRATROP
Update, November 20, 2013, 11:15 a.m. Eastern: Melissa has made the transition (PDF, technical) to a tropical storm, per the NHC forecasters, with sustained winds of 60 mph and a central pressure of 988 mb. It will only last for 24-36 hours, they think.
This transition wasn’t unexpected, but the forecast track has shifted dramatically. It’s heading for Europe now (possibly in Portugal), though most probably will extratropical by the time it gets there.
Update, November 18, 2013, 10:22 a.m. Eastern: The NHC jumped the gun a bit with their 11 a.m. bulletin, but we do have Subtropical Storm Melissa as of this morning!
It could develop into a tropical storm in the next 48 hours, but the experts think it unlikely to reach hurricane strength, though they’re not ruling that out. It will remain over the central and then northern Atlantic, not threatening land (UK and Europe are getting a break!) until it reaches, maybe, Greenland.
It’s late in the year, but hurricane season lasts until the end of November in the Atlantic Basin and the National Hurricane Center is watching a big low pressure system hundreds of miles southeast of Bermuda that’s packing gale-force winds and could develop.
It might turn into either a tropical cyclone (tropical storm or hurricane) or a subtropical cyclone. Either way, the meteorologists would give it a name: Melissa.
Here is the NHC expert’s take on things right now:
ABNT20 KNHC 172329
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
700 PM EST SUN NOV 17 2013
FOR THE NORTH ATLANTIC…CARIBBEAN SEA AND THE GULF OF MEXICO…
A NON-TROPICAL LOW PRESSURE SYSTEM LOCATED OVER THE CENTRAL ATLANTIC
OCEAN ABOUT 850 MILES EAST-SOUTHEAST OF BERMUDA IS PRODUCING WINDS
TO GALE FORCE. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR THIS
LOW TO ACQUIRE SUBTROPICAL OR TROPICAL CHARACTERISTICS DURING THE
NEXT FEW DAYS WHILE IT MOVES SLOWLY NORTH-NORTHWESTWARD TO
NORTHWARD. THIS SYSTEM HAS A MEDIUM CHANCE…50 PERCENT… OF
BECOMING A SUBTROPICAL OR TROPICAL CYCLONE DURING THE NEXT 48
HOURS…AND A HIGH CHANCE…70 PERCENT…OF BECOMING A SUBTROPICAL
OR TROPICAL CYCLONE DURING THE NEXT 5 DAYS.