Tropical Storm Danny is a girly-man. It has some pretty robust convection but its well east of the center. By Friday afternoon the low level circulation was completely exposed and the hurricane hunter reported a central pressure at a pedestrian 1007 mb. It’s also running out of time for development. As a deep trof starts to invade the eastern two thirds of the nation, southwesterly winds ahead of the trof will increase and end any chance for upper level support. That upper trof that has been plaguing Danny from the beginning just never went away as the models had been thinking. The storm spent most of the day drifing to the west, which the models also never figured out, but with all of the convection going on east, it may be trying to reform a center. By late in the day, it started a more northern drift. Either way, the modeling data does not call for real significant increase in intensity as it moves up the Southeast and mid Atlantic coasts. So, the National Hurricane Center isn’t even bothering to change the tropical storm watch for the outer banks of North Carolina to a warning. If it reforms farther east, then there is almost no chance of it affecting the US. But, the conventional models all still run it along the Carolina coast. It quickly loses its tropical characteristics, which never really fully developed anyway. But, in this case its a so what situation because the models want to run it along the Northeast Coast and have it deepen from its current 1007 mb down to about 994mb and then move it into Nova Scotia. So, there could be some heavy rain, gusty winds and high seas…in some regards similar to Bill except the seas probably won’t be running as high.
There is another tropical cyclone trying to get going way out about 300 miles WSW of the Cape Verde Islands. That one has some potential and its farther south than previous cyclones that have formed of late. That would decrease the potential for it getting caught up in any unseasonal trofs that move into the Atlantic. But, its way out there and there are lots of possibilities. At this point, I would almost hazard a suggestion that it has a better chance of adversely affecting the US than Danny…but it so far out that one can’t really say that so I won’t. 9 of 15 tropical cyclone models make it a Tropical Storm in 48 hours with 6 of those eventually making it a hurricane, two claiming Cat 2. We’ll see. Man proposes, God disposes.
WTNT45 KNHC 282035
TROPICAL STORM DANNY DISCUSSION NUMBER 10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052009
500 PM EDT FRI AUG 28 2009
AFTER STALLING EARLIER THIS AFTERNOON…THE CENTER OF DANNY IS
FINALLY MOVING SLOWLY NORTHWARD OR NORTH-NORTHEASTWARD. DATA FROM AN
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SUGGEST THAT DANNY IS
STILL A MINIMAL TROPICAL STORM…BASED ON A 33-KT OBSERVATION FROM
THE SFMR IN THE SOUTHEASTERN QUADRANT.
THE INTENSITY FORECAST SHOWS THE POSSIBILITY FOR A LITTLE
STRENGTHENING IN THE SHORT TERM…AS THE INCREASING UPPER-LEVEL
DIVERGENCE COULD SUPPORT THE REDEVELOPMENT OF CONVECTION NEAR THE
CENTER. HOWEVER…BY 24 HOURS…DANNY WILL BE MOVING INTO A VERY
UNFAVORABLE ENVIRONMENT FOR A TROPICAL CYCLONE…WITH THE SHIPS
MODEL SHOWING WIND SHEAR INCREASING TO 35 KT BY THAT TIME. BY 36
HOURS…DANNY WILL BE OVER SSTS OF NEAR 20C…AND INTERACTING WITH
THE DEEP-LAYER BAROCLINIC TROUGH OVER THE EASTERN U.S. MOST OF
THE LATEST GLOBAL MODELS AND PHASE SPACE DIAGRAMS SHOW THAT DANNY
WILL BE EXTRATROPICAL BY THAT TIME. THERE IS THE POTENTIAL FOR SOME
INTENSIFICATION OF DANNY LATE IN THE FORECAST PERIOD AS AN
EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC.
THE GUIDANCE WAS INITIALIZED WITH A LONG TERM MOTION OF 315/08…
AND REMAINS IS GOOD AGREEMENT ON THE RAPID ACCELERATION OF DANNY
NORTHWARD AND NORTH-NORTHEASTWARD. IN FACT…THE MODEL SPREAD IS
SMALLER NOW THAN IT WAS EARLIER TODAY. THE OFFICIAL TRACK IS SLOWER
THAN THE MODEL CONSENSUS THROUGH MOST OF THE PERIOD DUE TO THE SLOW
INITIAL MOTION. FROM 24 TO 36 HOURS…THE NEW FORECAST IS SHIFTED
TO THE RIGHT OF THE PREVIOUS FORECAST TRACK…BUT DANNY IS STILL
EXPECTED TO MOVE CLOSE TO THE SOUTHEASTERN COAST OF NEW ENGLAND AND
APPROACH NOVA SCOTIA IN 36-48 HOURS.
DATA FROM THE AIRCRAFT SUGGEST THAT THE ONLY 34-KT WINDS ARE LOCATED
IN THE SOUTHEASTERN QUADRANT. THE LACK OF WINDS ON THE WEST SIDE OF
DANNY LESSEN THE THREAT FOR TROPICAL STORM WIND REACHING THE NORTH
CAROLINA OUTER BANKS. HOWEVER…THE WATCH IS LEFT IN PLACE IN CASE
THE WIND FIELD BECOMES BETTER DEFINED ON THE WESTERN SIDE OF DANNY.
AS DANNY BECOMES EXTRATROPICAL…ITS EXPANDING WIND FIELD MAY
IMPACT THE COAST OF NEW ENGLAND. THESE POTENTIAL IMPACTS WILL BE
HANDLED WITH GALE WARNINGS AND OTHER PRODUCTS ISSUED BY LOCAL NWS
OFFICES IN THAT REGION.
FORECAST POSITIONS AND MAX WINDS
INITIAL 28/2100Z 30.4N 75.4W 35 KT
12HR VT 29/0600Z 32.7N 75.8W 40 KT
24HR VT 29/1800Z 37.3N 73.2W 40 KT
36HR VT 30/0600Z 41.9N 68.2W 40 KT…EXTRATROPICAL
48HR VT 30/1800Z 46.5N 61.4W 40 KT…EXTRATROPICAL
72HR VT 31/1800Z 50.5N 49.5W 40 KT…EXTRATROPICAL
96HR VT 01/1800Z 53.0N 35.0W 45 KT…EXTRATROPICAL
120HR VT 02/1800Z 55.0N 22.0W 50 KT…EXTRATROPICAL