This is Interesting...at Least Worth a Look - NCEP Ensembles

[Steve H.]

HPC Extended Forecast Discussion
Posted by Michael P. Pitt-HurricaneMike on 9/2/2003, 11:30 am

HPC still talking about the possibility of the 500 mb holding through the period.
THE NCEP ENSEMBLE MEAN IS THE WRN MOST OUTLIER
THIS PERIOD HOLDING ENERGY BACK OVER THE LWR MS
VLY THROUGH THE PERIOD AND KEEPING HEIGHTS HIGH
OVER THE EAST... RESULTING IN A MUCH STRONGER 500
MB RIDGE OVER THE WRN ATLANTIC. THE ENSEMBLE
MEAN THEN WOULD BE SLOWER/WEAKER AND NEVER
REALLY ALLOWING THE FRONT TO EXIT THE ERN
SEABOARD BUT MORE IMPORTANTLY GUIDE FABIAN ON
A MORE WESTWARD TRACK. THE MED RNG GUIDANCE
LATE LAST WEEK HAD A REAL DIFFICULT TIME WITH THE
STRENGTH OF THIS RIDGE AND FCSTED GRACE TO
ENTER INTO LA. THE RESULTANT WAS TX AND THE ONLY
MODEL SUGGESTING THIS IDEA WAS THE ECMWF WHICH
HAD THE STRONGER RIDGE.

THE ECMWF KEEPS THE ZONAL FLOW ACTIVE
THROUGHOUT THE PERIOD... MOVING THE SHORT WAVE
ENERGY OVER THE EAST OUT INTO THE NRN ATLANTIC
VERY QUICKLY BUT ALSO HOLDS ENERGY AWAY FROM
THE UPPER FLOW OVER THE LWR MS VLY. FABIAN AS A
RESULT WOULD STILL MOVE AWAY FROM THE COAST.
THE 06Z GFS AND UKMET HOLD AND DEVELOP A
STRONGER 500 MB FEATURE OVER THE GRT LAKES AND
DIG THE SHORT WAVE INTO THE MID-ATL... BASICALLY
KNOCKING DOWN THE RIDGE AND DRIVING HEIGHTS
DOWN IN THE EAST... AND HELP KEEP FABIAN AWAY
FROM THE EAST COAST AND LIFT THE TROPICAL
CYCLONE INTO THE ATLANTIC.

THE 00Z GFS SEEMS LIKE THE PERFECT COMPROMISE...
HOLDING ONTO SHORT WAVE ENERGY... TRAPPING IT
OVER THE LWR MS VLY/TN VLY AND SHEARING OUT THE
ERN TROUGH AXIS BUT ALSO HOLDING ONTO MORE
RIDGING OVER THE ATLANTIC. MORE REASONING ON
GOING WITH THIS SOLUTION IS... WHEN HEIGHTS REMAIN
RATHER LOW OR LWR MORE OVER NRN CANADA... LIKE
THEY ARE THIS PERIOD... VERY STRONG RIDGING
USUALLY EXISTS OVER THE ATLANTIC. THIS WOULD
SUPPORT THE NCEP ENSEMBLE MEAND/00Z GFS AND
ECMWF BUT THE ECMWF IS MUCH DIFFERENT ON THE
DEVELOPMENT OF THE ERN PAC TROUGH... MOVING
INTO THE WRN US DURING THE PERIOD... SLOWER THAN
THE 00Z GFS AND NCEP ENSEMBLE MEAN. THE 00Z
SEEMS THE BEST COMPROMISE AT THIS TIME BUT THE
ENSEMBLES ARE WORTH OUR ATTENTION. PLEASE
REFER TO DISCUSSIONS FROM THE NHC ON HURRICANE
FABIAN.

[Stormsfury]

The ETAxx had a depiction of Fabian moving slowly NW through 168 hours...and just barely crossing 35N through the period and puts it precariously close to Cape Hatteras. I don't know the track record of the ETAxx since I usually don't give it a looksee.

120 hrs


144 hrs


168 hrs

SF