HPC ...PRELIMINARY MODEL DISCUSSION... Strong Ridge in Place

[KatDaddy]

A strong ridge through next week over New England and W Atlantic would mean a US landfall along SE US. Dont see the ridge pushing this into GOM. If I lived along the SE US Coast (FLA to NC) I would pay very close attention to Isabel next week.

...PRELIMINARY MODEL DISCUSSION...

THE 500MB LONGWAVE PATTERN OF A TROF OVER W-CENTRAL
NOAM....WITH RIDGES IN THE NEW ENG/WRN ATLANTIC AND ERN
PACIFIC...WILL MAINTAIN AMPLITUDE OVER THE NEXT WEEK. THE
STRONG MEAN RIDGE OVER NEW ENG AND THE WRN ATLANTIC COULD
HAVE SERIOUS IMPLICATIONS ON THE TRACK OF HURCN ISABEL
EARLY NEXT WEEK.

[Stormcenter]

But Kat Daddy she is ONLY moving at 9mph! How long will the conditons remain the same if she continues to slow her speed. No U.S. location is in the clear now or for least another week unless she makes a radical curve to the NE right now and that doesn't look likely. I guess you forgot about Betsy, Elena, and Andrew?

[Steve H.]

When was the discussion issued concerning the 500 mb ridge?

[jfaul]

When was the discussion issued concerning the 500 mb ridge?

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1035 AM EDT THU SEP 11 2003

VALID 12Z MON SEP 15 2003 - 12Z THU SEP 18 2003

...PRELIMINARY MODEL DISCUSSION...

THE 500MB LONGWAVE PATTERN OF A TROF OVER W-CENTRAL
NOAM....WITH RIDGES IN THE NEW ENG/WRN ATLANTIC AND ERN
PACIFIC...WILL MAINTAIN AMPLITUDE OVER THE NEXT WEEK. THE
STRONG MEAN RIDGE OVER NEW ENG AND THE WRN ATLANTIC COULD
HAVE SERIOUS IMPLICATIONS ON THE TRACK OF HURCN ISABEL
EARLY NEXT WEEK.

OUR DECISION FOR THIS FIRST RELEASE OF SEA LEVEL PROGS WAS
TO GO WITH ABOUT A 50-50 BLEND OF THE 12Z/10 ECMWF AND
06Z/11 GFS THRU WED DAY 6. FIRST...THIS BLEND CORRECTS THE
APPARENT ERROR OF THE 00Z/11 GFS OF BEING TOO FAST AND
LACKING IN AMPLITUDE WITH A SHORTWAVE REACHING THE MS VLY
ON MON DAY 4. SECOND...THIS BLEND CORRECTS THE TENDENCY OF
THE 06Z/11 GFS TO BE TOO FAR S OVER THE UPPER OH VLY TUE
DAY 5 WITH THIS SAME SHORTWAVE...GIVEN THE STRONG MEAN
500MB RIDGE OVER NEW ENG AND THE ADJACENT ATLANTIC. THE
12Z/10 ECMWF DOES A MUCH MORE REALISTIC JOB OF KEEPING A
STRONG RIDGE OFF THE NEW ENG COAST DAY 6 THAN THE LATEST
GFS RUNS.

...E OF THE ROCKIES..

OUR BIGGEST ADJUSTMENT TO THE 00Z/11 GFS MASS FIELDS AND
THEIR DERIVED MOS PRODUCTS WAS TO REFLECT A SLOWER EWD
TRANSLATION OF THE UPPER TROF DROPPING INTO THE
NRN/CENTRAL PLAINS STATES SUN DAY 3. THIS SLOWER TROF THEN
MOVES EWD ACROSS THE ERN CONUS MON-TUE...DAYS 4-5.

THE OTHER ADJUSTMENT IS THAT POPS/QPF ALONG THE MID
ATLANTIC/SE COASTS DAY 6 AND ESPECIALLY DAY 7 ARE EXPECTED
TO BE HIGHER THAN IMPLIED BY THE GFS...AS TROPICAL
MOISTURE FROM HURCN ISABEL BEGINS TO OVERRUN A STATIONARY
FRONTAL BOUNDARY.

...ROCKIES WWD...

NO LARGE SCALE SIGNIFICANT ADJUSTMENTS MADE TO 00Z/11 GFS
MASS FIELDS.

FLOOD

GRAPHICS AVAILABLE AT http://WWW.HPC.NCEP.NOAA.GOV

[Guest]

But Kat Daddy she is ONLY moving at 9mph! How long will the conditons remain the same if she continues to slow her speed. No U.S. location is in the clear now or for least another week unless she makes a radical curve to the NE right now and that doesn't look likely. I guess you forgot about Betsy, Elena, and Andrew?

That's exactly true and the models are trending slight to the north - they Do NOT at this time take the storm to EC. Only one does but how valid is it 180 hours? Not much. Everyone needs to remind on the outlook and she is slowin down - went from 10 mph to 9 mph - could get even slower and timing is everything - we all know that....

[chris_fit]

The more Izzy slows down........

1. is that good b/c that'll give time for the trough to come down from the west and bring it north?
2. is that bad b/c it'll give time for the ridge to build north of it and push it west?

~Chris

[Stormcenter]

Any of the above is true but the latter is what scares me for SE Florida.

[Coriolis2003]

The more Izzy slows down........

1. is that good b/c that'll give time for the trough to come down from the west and bring it north?
2. is that bad b/c it'll give time for the ridge to build north of it and push it west?

~Chris

The slower movement only increases the likelihood that an East Coast trough will deflect it northwards and away. This blocking ridge pattern will not last forever.

[Steve H.]

Thanks jfaul!