5 P.M. DISCUSSION CASTS DOUBT ON SHARP NW TURN.........

[dixiebreeze]

Hurricane Isabel Discussion Number 27


Statement as of 5:00 PM EDT on September 12, 2003


Reports from Air Force reserve and NOAA hurricane hunter aircraft
confirm that Isabel is a category 5 hurricane. Maximum observed
flight-level winds so far are 156 kt at 700 mb...supporting surface
winds near 140 kt. The eye is 30 nm wide with a closed Wall and a
minimum pressure of 920 mb. The initial intensity thus remains 140
kt...which agrees with satellite intensity estimates. It should be
noted that Isabel looks a little less organized in satellite
imagery than it did 24 hr ago. Thus it might have been a little
stronger yesterday.
The eye has recently nudged to the right...but the longer term
motion remains 270/8. There is little change in the synoptic
pattern or reasoning from the previous forecast. Isabel is
currently south of a deep layer ridge...with an anticyclone seen
in water vapor imagery near 29n55w...and upper-level troughs along
68w and 42w. In the short term...this should produce a westward to
possibly west-northwestward motion. Upstream...a deep layer
cyclonic circulation is over the southeastern United
States with a mid/upper-level ridge building over southeastern
Canada. Large-scale guidance forecasts the southeastern system to
move northward...leaving a weakness on the southwest side of the
Canadian ridge as it builds eastward into the Atlantic. NHC track
guidance agrees on a westward to west-northwestward motion through
72 hr... and to that time the forecast track is an update of the
previous package. Considerable divergence occurs after 72 hr. The
UKMET calls for a gradual turn toward the northwest by 120 hr in
response to the weakness. The GFS...NOGAPS...GFDL...and Canadian
models all call for a more northward motion. Since all models keep
some deep layer ridging over the northwest Atlantic north and
northeast of Isabel...so sharp of a turn continues to look a little
dubious. Thus...the 3-5 day official forecast will lean toward the
UKMET. It should be noted that the UKMET is calling for more
northward motion after 96 hr than forecast earlier...and the
official forecast is thus shifted to the right of the previous
forecast after 72 hr. Given the divergence of the models at 120
hr...it is still too early to speculate which parts...if any...of
eastern coast of the United States may get affected by Isabel.
Isabel is forecast to remain in a warm-water low-shear environment
for roughly the next 72 hr. During that time...the intensity
should be controlled mainly by eyewall replacement cycles. The
intensity forecast will thus call for a slow weakening through that
time based on continuity from previous forecasts and climatology.
After 72 hr...the GFS and ships models suggest Isabel may be
affected by southwesterly vertical shear. Based on this...the
intensity forecast will call for a somewhat faster weakening after
72 hr.
Wind radii have been revised on the basis of aircraft data. It
should be noted that large-scale models all forecast Isabel to grow
in size beyond 72 hr even if the inner core weakens.
Forecaster Beven

forecast positions and Max winds

[WeatherEmperor]

Looks like Florida is becoming all-clear.

[dixiebreeze]

No, not with all the uncertainties remaining after the 5 p.m. disc. Right now I have a little more faith in the ridge than I do in the trough, but we'll see.

I have to compare a storm this size with a locomotive going full tilt -- nothing stops it.

[Stormcenter]

WeatherEmperor


Now I must have missed that. Where does it state in the NHC discussion that Florida is "all clear"?

[Josephine96]

You know these "all clear for Florida" signals have got to stop cause it aint the truth till it officially happens..

Dixie, there was a guy on Go Pbi who always called "all clear for Florida" way too early.. I forgot his name.. wasn't it like "dyno mat" or something lol

[~SirCane]

With Fabian, everyone was 100% confident that he was going to turn to the North.

I see no confidence in that at all with Isabel. I see a lot of uncertainty.

[dixiebreeze]

Yes, I think it was. I'd never say "all clear" until it's "all clear."

[Tommedic]

Let's all be honest with ourselves.... If there was any way to predict landfall or guarantee lack of this far out we would have nothing to banter about. I believe threat to Fl is reducing daily as I watch everything. But you notice that I said reduced and not eliminated. I do begin to get a feel that SC/NC region will be impact area. Partly gut and partly watching clouds, her spin, etc. Been wrong before.. But I'm afraid I've been right too. Guess it could have been luck.

Anyway, my first thought in all of this is to pray for all of us. As I've said before, I would love to get to look at a storm like this, but truly I would like it to go out to sea or just weaken before landfall.

[seaswing]

Think he's still there.... Dyno Storm or Why ban dynosauer or somthing like that. As a native of Florida...... and all natives know..."you never say never"

[dixiebreeze]

The bottom line on this 5 p.m. discussion is that no one really knows much more than they did before it came out. Isabel has decided to make things difficult for us.

She's a locomotive and may be strong enough to control the signals and switches.

[seaswing]

yep Dixie.....she's is big enough to make her own decisions here. Isn't that the "creating it's own environment theory"?

[ColdFront77]

Let's all be honest with ourselves.... If there was any way to predict landfall or guarantee lack of this far out we would have nothing to banter about.

There would still be a number of us coming here to chat about a storm and/or even the possible development of a storm.

Otherwise, the USA Weather and Off Topic Forum would have more activity, as well as the other forums from time to time.