THE RIDGE RULES! NHC 11 A.M. SAYS MODELS NOT.........

#1 Postby **dixiebreeze** » Sat Sep 13, 2003 9:50 am

HANDLING THE RIDGE WELL. WEST FOR AT LEAST 36 MORE HOURS.......

Hurricane Isabel Discussion Number 30

Statement as of 11:00 am EDT on September 13, 2003

Isabel has completed an eyewall replacement cycle based on a
13/1102z SSMI overpass showing a closed 35 nmi diameter eye. The
intensity is maintained at 130 kt based on continuity with the
previous data...a consensus satellite intensity estimate of 127
kt...raw ODT values of t6.5...or 127 kt...and the fact that the eye
has cleared out nicely and surrounding eyewall cloud tops have
cooled to -70c and colder once again. Next recon mission is at 18z.

The initial motion is 280/08. Over the past 72 hours...Isabel has
been moving at 275 degrees. The hurricane made a slight northward
wobble during the earlier eyewall replacement cycle...but it now
appears to have resumed a 275-280 degrees motion. All of the global
and regional models have had a distinct right-of-track bias by as
much as 10 degrees...and each model run has been a little farther
west and slower. The exception is the 06z GFDL run which made a
major shift westward by more 200 nmi in the later forecast periods
...While the 06z NOGAPS model accelerated Isabel and has the
hurricane onshore the southeast coast of North Carolina in 120
hours. However...the model consensus is slower and farther west
before a turn to the northwest occurs in the later periods. The
models obviously have not been handling the strong ridging to the
north of Isabel very well. This may be due to the outflow on the
north side being drawn northward and sinking along 30n-33n...which
may have helped to strengthen the subtropical ridge. Water vapor
imagery indicates this pattern has persisted for more than 72 hours
and continues to shift westward with Isabel. Therefore...a general
westward motion should continue for another 36 hours or so.
Afterwards...there remains considerable divergence among the models
and how they handle the current shortwave trough/low over the
southeastern U.S. Water vapor imagery indicates the trough has
become negatively tilted in an east-west orientation. This would
suggest that the low should begin to lift out and allow the ridge
north of Isabel to gradually build westward...which is similar to
the 06z GFS...GFDL...and ETA...and 00z UKMET solutions. The key
will be how the central U.S. Trough evolves and how deep it digs
into the southern U.S. And Gulf of Mexico. The official forecast
was adjusted slightly to the left of and slower than the previous
forecast...which is consistent with the guna model consensus.
However...it is still too early to determine when or where Isabel
will make landfall. Hopefully...the NOAA Gulfstream-IV synoptic
data mission at 14/00z will provide better model convergence.

Although Isabel has a rather large eye diameter...conditions appear
favorable for at least some slight additional strengthening over
the next couple of days as the hurricane moves over warmer water.

Forecaster Stewart

zoeyann · #2 Postby **zoeyann** » Sat Sep 13, 2003 9:52 am

This is bad for Florida and good for the upper east coast right?

Josephine96 · #3 Postby **Josephine96** » Sat Sep 13, 2003 9:53 am

Zoey ann- It sounds that way.. If the ridge builds westward, Isabel will move westward and us Floridians will get an up close and personal look at her..

#4 Postby **dixiebreeze** » Sat Sep 13, 2003 9:53 am

I THINK THAT'S EXACTLY RIGHT. IF SHE TURNS VERY MUCH N. IT WON'T BE DUE TO ANY TROUGH, AT LEAST NOT AT THIS POINT. THAT RIDGE IS SIMPLY TOO STRONG AND MOVING IN TANDEM WITH ISABEL.

zoeyann · #5 Postby **zoeyann** » Sat Sep 13, 2003 9:57 am

This is what I was worried about. Never trust a steering current they are too fickleLOL

JetMaxx · #6 Postby **JetMaxx** » Sat Sep 13, 2003 9:59 am

What it means is EVERYONE needs to closely monitor the latest advisories...

Isabel is a slow mover...and unless it gets north of latitude 30N, is likely to remain a slow mover....which will give whoever is ultimately in it's path plenty of time to prepare (ie. -3 or 4 days).

The folks who need to be most vigilant are those from South Carolina to New England....BECAUSE IF Isabel makes it to 30N and gets caught by a trough, it could accelerate northward (move faster toward the coastline) -- as many major hurricanes have done in the past (Donna, Hazel, Carol, Bob, Hugo, etc).

#7 Postby **dixiebreeze** » Sat Sep 13, 2003 10:02 am

She's getting better organized again says Stewart in the 11 a.m. Advisory:

Statement as of 11:00 am AST on September 13, 2003

...Powerful category 4 Hurricane Isabel getting a little better
organized as it moves westward...

at 11 am AST...1500z...the center of Hurricane Isabel was located
near latitude 22.2 north...longitude 61.5 west or about 405 miles
...650 km...northeast of San Juan Puerto Rico.

Isabel is moving toward the west near 10 mph...17 km/hr...and this
general motion is expected to continue for the next 24 hours.

Maximum sustained winds are near 150 mph...240 km/hr...with higher
gusts. Some slight strengthening is possible during the next
24 hours. An Air Force reserve hurricane hunter aircraft is
scheduled to investigate the dangerous hurricane this afternoon.

Hurricane force winds extend outward up to 85 miles...140 km...
from the center...and tropical storm force winds extend outward up
to 175 miles...280 km.

The estimated minimum central pressure is 935 mb...27.61 inches.

Large ocean swells and dangerous surf conditions are likely over
portions of the Leeward Islands...the Virgin Islands...Puerto Rico
...And the Dominican Republic over the next several days.

Repeating the 11 am AST position...22.2 N... 61.5 W. Movement
toward...west near 10 mph. Maximum sustained
winds...150 mph. Minimum central pressure... 935 mb.

It's conceivable she could retain her Cat. 5 status IMO.

The next advisory will be issued by the National Hurricane Center
at 5 PM AST.

Forecaster Stewart

#8 Postby **wxman57** » Sat Sep 13, 2003 10:06 am

I don't know what you are seeing in that discussion. The building ridge is implying a greater threat to the MID Atlantic coast Vs. heading out to sea, not a greater threat to Florida vs. the Hatteras area. But it seems that this is being interpreted that Florida is now a target? I don't think so. Remember, the NHC wasn't sure if Isabel would head out to sea and miss the U.S. before. The new discussion just says that an out to sea track is unlikely, so their track is now aiming for the Mid Atlantic Coast. You don't see their track pointing at Florida, do you?

#9 Postby **dixiebreeze** » Sat Sep 13, 2003 10:11 am

wxman, no I don't see it pointing at Florida and I don't expect to until Isabel is 2 to 3 days from landfall. I also don't think it will likely be S. Fla., but anywhere from West Palm Beach north. There is trending going on IMO -- but we have a while to wait, I agree.

zoeyann · #10 Postby **zoeyann** » Sat Sep 13, 2003 10:14 am

Actually I was reading this as worse for Florida because I never believed she would go out to see, but you bring up an excellent point when you account for that line of thinking. Everything is relative, and the more perspective the better. Thanks! (but I still think it looks bad for central Florida)

#11 Postby **dixiebreeze** » Sat Sep 13, 2003 10:15 am

Isabel is clearly picking up steam again:

http://www.ssd.noaa.gov/PS/TROP/DATA/RT ... IR4/20.jpg

#12 Postby **Air Force Met** » Sat Sep 13, 2003 10:23 am

No zoeyann...it's bad news for the EC. IT means that Izzy will not be a fish. The trof and the ridge will put her in a squeeze and when she moves up the EC...she will do so at 20 kts if not more. Not a lot of evac time. Be prepared if anyone lives from Cape Hat northward.

If the NHC honestly thought this hurricane had any remote chance of coming close to FL...they would stall it near the Bahamas for 2 days. They didn't. South Fl is not going to see this storm. The ridge building north means it will keep it from recurving into the ocean.

#13 Postby **Stephanie** » Sat Sep 13, 2003 10:28 am

Air Force Met wrote:No zoeyann...it's bad news for the EC. IT means that Izzy will not be a fish. The trof and the ridge will put her in a squeeze and when she moves up the EC...she will do so at 20 kts if not more. Not a lot of evac time. Be prepared if anyone lives from Cape Hat northward.

If the NHC honestly thought this hurricane had any remote chance of coming close to FL...they would stall it near the Bahamas for 2 days. They didn't. South Fl is not going to see this storm. The ridge building north means it will keep it from recurving into the ocean.

The stronger the ridge, the better the steering mechanism for Isabel as well to shift more northward in time, right?

ameriwx2003 · #14 Postby **ameriwx2003** » Sat Sep 13, 2003 10:32 am

I take the TPC advisories as meaning that the Fish option is out. In the 5 AM advisory they made a strong statement that not one model brings this to Florida and that is still true. The trending seems to be that further up the Coast looks to be in trouble:):)

bev1 · #15 Postby **bev1** » Sat Sep 13, 2003 10:34 am

As always we just need to watch and wait. These storms seem to have a mind of their own and the weather patterns that determine direction then to be constantly changing.

blizzard20 · #16 Postby **blizzard20** » Sat Sep 13, 2003 10:44 am

Florida will will likely not get the Hurricane. The area likely too get Isabel is from virginia area towards southern New england area.
It will likely start moving fast when it reaches the Virginia coast area move more Northward towards the Southern New england area .

The ridge is very strong over the Altantic ocean but how far west will it expanded . It will expanded west but I think the storm will move Northward when its reaches the North Carolina area, Virginia area coast go up the Nj coast over Long Island into Wester ct. as a CAT 4 / 5.

#17 Postby **Air Force Met** » Sat Sep 13, 2003 10:51 am

Steph and AmeriWx: Yes and Yes

JetMaxx · #18 Postby **JetMaxx** » Sat Sep 13, 2003 10:53 am

blizzard20....have you checked the sea surface temps offshore the U.S. East Coast lately??

Diamond Shoals, NC...just east of Cape Hatteras is only reading 75°.....Offshore Virginia Beach and Ocean City the sst is 72-74°, and only 68° south of Long Island...

Son, the ONLY way this hurricane will be a cat-4 at landfall on Long Island is if it races northward at 60+ mph once it passes the north wall of the Gulf Stream...and that ain't gonna happen. A category 5 hurricane is out of the question for New England.....no way!

~SirCane · #19 Postby **~SirCane** » Sat Sep 13, 2003 10:55 am

but Florida is NOT out of the woods. NONE whatsoever.

If anything, Florida is more of a threat now than it was early this morning.

calidoug · #20 Postby **calidoug** » Sat Sep 13, 2003 10:57 am

No, the trending seems to be that they backed off that 5am advisory re:Florida.

Note all the mention of further S and W than expected, and models changing to the LEFT now. Also a mechanism is discussed for why the ridge is holding. AND they've got the storm strengthening again as the water warms. Stronger storm = more ridge pumping.

If that trough lifts out, and the ridge stays strong, you're left with W to WNW movement until something else happens.

And that means those in FL better not let down their guard just yet.

Recall Andrew... with that storm, it was already AT 25N, and the models kept showing a turn... it didn't turn.

THE RIDGE RULES! NHC 11 A.M. SAYS MODELS NOT.........

THE RIDGE RULES! NHC 11 A.M. SAYS MODELS NOT.........

Huh?

This statement means out to sea is gone it hits the coast

Sorry folks..

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