My 5 p.m. EST WED Isabel analysis & forecast

JetMaxx · #1 Postby **JetMaxx** » Wed Sep 17, 2003 3:32 pm

Isabel appears to be beginning to intensify...and also increase in forward speed in response to a developing steering current between high pressure over New England/ southeastern Canada and a trough digging southward over the Central U.S. -- which will accelerate the hurricane toward eastern North Carolina and Virginia.

I don't understand the National Hurricane Center's reasoning for lowering Isabel's estimated maximum sustained winds from 110 mph to 105 at 2 p.m.; especially in light of flight level wind reports of 139 mph in the southeast eyewall, and 132 and 131 mph in the northest eyewall measured by reconnisance aircraft this afternoon....along with a central pressure that has fallen from 957 mb to 955 mb since this morning.

I believe that Isabel is already a major hurricane....those flight level wind reports at 10,000 feet correspond to 115-120 mph on the surface. However, in the interest of compatibility...I'm initiating Isabel's 5 p.m. intensity as 110 mph and 955 mb....and feel confident the hurricane will continue to strengthen and arrive on the Carolina coast tomorrow as a strong category 3 hurricane capable of major damage and extensive storm surge flooding.

I urge, in the strongest terms....if you live in a vunerable area....on a barrier island, low ground, or areas that are flood prone in the HURRICANE WARNING AREA, please EVACUATE AS SOON AS POSSIBLE...DON'T DELAY. Hurricane Isabel will pickup forward speed and could arrive sooner than I'm forecasting.

Isabel is a very large hurricane....and I expect hurricane force winds and high tides over much of the mid-Atlantic coastal areas from North Carolina to Maryland and Delaware, including the southern portion of Chesapeake Bay. The large size of the hurricane will also increase the threat of serious flooding....both near the coast and well inland along the storm track.

CURRENT:

WEDNESDAY SEP 17

5 PM EST...31.2N - 73.1W...110 MPH

FORECAST:

THURSDAY SEP 18

5 AM EST...33.2N - 74.8W...120 MPH

11 AM EST..35.0N - 76.4W...125 MPH (Landfall near Cedar Island, NC)

5 PM EST...36.6N - 78.0W....90 MPH (Near Roanoke Rapid, NC)

FRIDAY SEP 19

5 AM EST...39.5N - 79.5W....55 MPH (Over extreme western Maryland)

5 PM EST...45.0N - 78.0W....50 MPH...EXTRATROPICAL
(Near Petersborough, Ontario Canada)

#2 Postby **Mattie** » Wed Sep 17, 2003 3:38 pm

JetMaxx - can you give me some idea of the diameter of the hurricane on land terms that I am familiar with? I am from Louisiana and currently reside in Texas. . . . possibly giving a land reference along biloxi/gulfport would be helpful - if you are familiar with that area. . .

Or anyone?

Thanks!

Wolfman21 · #3 Postby **Wolfman21** » Wed Sep 17, 2003 3:39 pm

Im from Person County, NC. Im j/w what you think I will get as far as winds and rain??

Its just north of the triangle, thanx

Mello1 · #4 Postby **Mello1** » Wed Sep 17, 2003 3:45 pm

I don't understand the National Hurricane Center's reasoning for lowering Isabel's estimated maximum sustained winds from 110 mph to 105 at 2 p.m.; especially in light of flight level wind reports of 139 mph in the southeast eyewall, and 132 and 131 mph in the northest eyewall measured by reconnisance aircraft this afternoon....along with a central pressure that has fallen from 957 mb to 955 mb since this morning.

Could this be the just the wind gust speeds? The 5pm stats are at 105, gusting to 135. I'm very far from being knowledgable about this, but doesn't that seem to be a big spread between sustainable speed and gust?

PuertoRicoLibre · #5 Postby **PuertoRicoLibre** » Wed Sep 17, 2003 3:55 pm

Truly a mystery to me. When they don't have data they tend to act conservative until the recon comes in (and they tell you that's what they are doing) which is often criticized as too dismissive of other data sources. Here they have the ACTUAL recon data and they dismiss it completely and keep the data on the conservative side. And I ask, on what FACTUAL basis can they justify throwing every Recon report this afternoon into the trashcan? Is there one?

Bane · #6 Postby **Bane** » Wed Sep 17, 2003 4:06 pm

From TPC:

IF FLIGHT-LEVEL OBSERVATIONS WERE ALL WE HAD...ISABEL WOULD BE A
CATEGORY THREE HURRICANE. THE HURRICANE HUNTER AIRCRAFT THIS
AFTERNOON FOUND A NUMBER OF SPOTS OF WINDS OF 110-120 KT. THIS
WOULD NORMALLY CORRESPOND TO SURFACE WINDS OF 100-105 KT.
HOWEVER...NUMEROUS DROPSONDE PROFILES IN THE HIGH WIND REGIONS OF
THE CIRCULATION SHOW A CONSISTENT AND UNUSUALLY STEEP FALL-OFF OF
WIND IN THE BOUNDARY LAYER. THIS IS CONSISTENT WITH THE MEAGER
CONVECTION IN THE HURRICANE CORE. BASED ON THESE PROFILES...THE
INITIAL INTENSITY IS SET AT 90 KT. THE UPPER-LEVEL OUTFLOW PATTERN
HAS BECOME FAVORABLE...AS WAS FORECAST BY THE GLOBAL MODELS...AND
IN FACT THE CIRCULATION ALOFT IS STRENGTHENING. HOWEVER...
THERMODYANAMIC FACTORS ARE LIMITING THE ABILITY OF ISABEL TO
COMPLETELY RESPOND TO THE FAVORABLE UPPER-LEVEL FORCING. THE
OFFICIAL FORECAST DOES NOT ANTICIPATE ANY SIGNIFICANT INCREASE IN
STRENGTH PRIOR TO LANDFALL...BUT SHOULD THERE BE A SUBSTANTIAL
INCREASE IN DEEP CONVECTION ISABEL COULD QUICKLY REACH CATEGORY
THREE STATUS.

JCT777 · #7 Postby **JCT777** » Wed Sep 17, 2003 4:12 pm

Perry - excellent analysis, and you may very well be right.

Bane - thanks for posting that piece of info. It does appear possible that Isabel will become a Category 3 hurricane prior to landfall.

Howlin · #8 Postby **Howlin** » Wed Sep 17, 2003 4:26 pm

Who or what is TPC?

JetMaxx · #9 Postby **JetMaxx** » Wed Sep 17, 2003 4:37 pm

Howlin wrote:Who or what is TPC?

It's just another name for the National Hurricane Center (TPC means "Tropical Prediction Center").

ColdFront77 · #10 Postby **ColdFront77** » Wed Sep 17, 2003 4:43 pm

I read (in one of my weather books) that the "National Hurricane Center" was renamed the "Tropical Prediction Center." I noticed that either one or the other or both together are used.

HuffWx · #11 Postby **HuffWx** » Wed Sep 17, 2003 4:46 pm

Person County NC...Just SE of Danville VA.

Should see winds of 40-50 sustained with gusts to 70. 2-4 inches rain.

Huff

JetMaxx · #12 Postby **JetMaxx** » Wed Sep 17, 2003 4:53 pm

Mattie..here's the NHC forecast wind profile just before landfall tomorrow..

64 KT (Hurricane Force)...100NE 80SE 60SW 90NW.

50 KT (Storm Force)...150NE 100SE 80SW 125NW.

34 KT (Tropical Storm Force)...275NE 250SE 150SW 210NW.

NOTE: Distances are in nautical miles.
If the eye of hurricane Isabel were making landfall at Gulfport/ Biloxi, hurricane force winds would extend along the gulf coast from Grand Isle and New Orleans, Louisiana eastward all the way to Pensacola; and tropical storm force winds would cover the gulf coast from LaFayette, Louisiana to the Florida coast south of Tallahassee.....

Isabel is a very large hurricane....as large as Carla and Hugo were at landfall.

-----------

Wolfman21 - the NWS office in Raleigh is forecasting winds of 35-55 mph in your area. If Isabel is as strong as I fear (125 mph) at landfall, I won't be surprised to see 50-70 mph gusts to the north and northeast of Raleigh-Durham.

Stormsfury · #13 Postby **Stormsfury** » Wed Sep 17, 2003 5:14 pm

BUT SHOULD THERE BE A SUBSTANTIAL INCREASE IN DEEP CONVECTION ISABEL COULD QUICKLY REACH CATEGORY THREE STATUS.

This is what I'm afraid of ... IF this happens ... I just got home and Isabel is looking like she's on a threshold point .. either way. This is why many of us including myself can't stress enough that preparations should be made as if Isabel WILL COME IN AS A STRONG CAT 3 ... There's no harm in overpreparing ...

SF

#14 Postby **JtSmarts** » Wed Sep 17, 2003 5:17 pm

Stormsfury I totally agree, but the biggest is problem is that most of the people in harms way have no idea what might happen in regards to a sudden increase in intensity. :o

My 5 p.m. EST WED Isabel analysis & forecast

My 5 p.m. EST WED Isabel analysis & forecast

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