11 AM NHC Discussion

[Guest]

Hurricane Frances Discussion Number 19


Statement as of 11:00 am EDT on August 29, 2004



the hurricane is in steady state and has a rather impressive
representation on satellite images with a large eye. Because there
is less intense convection surrounding the eye...the T-numbers have
decreased a little bit...suggesting that the hurricane may not be
as strong as a few hours ago. However...the initial intensity is
kept at 115 knots until direct measurements from the reconnaissance
plane become available later today. At this point...Frances could
either intensify a little bit more or could experience some
fluctuations in intensity. Nevertherless..it is expected to remain
as an intense hurricane.
As the GFS global model has been forecasting...Frances is now moving
slowly westward. The best estimate of the initial motion is 280
degrees at 8 knots. It appears that the expansion of the developing
subtropical ridge north of the hurricane is already occurring. This
pattern would steer the hurricane between the west and
west-northwest over the next five days. This forecast is
consistent with the GFS...UK...Canadian and the ECMWF global models
which are in very good agreement in building a strong subtropical
ridge and moving the hurricane dangerously north of Puerto Rico and
across the Bahamas to just east of Florida. The GFDL model is
beginning to show a little more northwesterly motion by the end of
the forecast period. This track would be less threatening for South
Florida and the Keys.

Forecaster Avila

forecast positions and Max winds

initial 29/1500z 18.6n 54.7w 115 kt
12hr VT 30/0000z 18.8n 56.1w 120 kt
24hr VT 30/1200z 19.5n 58.5w 120 kt
36hr VT 31/0000z 20.0n 61.0w 120 kt
48hr VT 31/1200z 20.5n 63.5w 120 kt
72hr VT 01/1200z 21.8n 68.7w 120 kt
96hr VT 02/1200z 23.5n 72.6w 125 kt
120hr VT 03/1200z 25.5n 76.5w 125 kt

[Rainband]

That would be good news if it happened, well for South Florida anyway

[Downdraft]

This is gonna be a real nail biter for Florida. At the moment everything from Miami to Jacksonville is up for grabs. The strength of the sub-tropical ridge is gonna determine who faces this buzz saw! No one can stop it but right now the whole state of Florida should be thinking about how to get out of it's way. Time to make plans folks you don't want to sit this one out if it's coming in from the Atlantic.

[Guest]

Its funny to me that while referring to the west turn they reference the GFS,UKMET,CMC & ECMWF but as it approaches South Fla they refer to only the GFDL.

[Derecho]

The GFDL had more of an initial west turn than most of the other models, actually.

And, of course, based on recent sat the "West turn" isn't as west as advertised.

[B-Bear]

Hurricane Frances Discussion Number 19


Statement as of 11:00 am EDT on August 29, 2004



the hurricane is in steady state and has a rather impressive
representation on satellite images with a large eye. Because there
is less intense convection surrounding the eye...the T-numbers have
decreased a little bit...suggesting that the hurricane may not be
as strong as a few hours ago. However...the initial intensity is
kept at 115 knots until direct measurements from the reconnaissance
plane become available later today. At this point...Frances could
either intensify a little bit more or could experience some
fluctuations in intensity. Nevertherless..it is expected to remain
as an intense hurricane.
As the GFS global model has been forecasting...Frances is now moving
slowly westward. The best estimate of the initial motion is 280
degrees at 8 knots. It appears that the expansion of the developing
subtropical ridge north of the hurricane is already occurring. This
pattern would steer the hurricane between the west and
west-northwest over the next five days. This forecast is
consistent with the GFS...UK...Canadian and the ECMWF global models
which are in very good agreement in building a strong subtropical
ridge and moving the hurricane dangerously north of Puerto Rico and
across the Bahamas to just east of Florida. The GFDL model is
beginning to show a little more northwesterly motion by the end of
the forecast period. This track would be less threatening for South
Florida and the Keys.

Forecaster Avila

forecast positions and Max winds

initial 29/1500z 18.6n 54.7w 115 kt
12hr VT 30/0000z 18.8n 56.1w 120 kt
24hr VT 30/1200z 19.5n 58.5w 120 kt
36hr VT 31/0000z 20.0n 61.0w 120 kt
48hr VT 31/1200z 20.5n 63.5w 120 kt
72hr VT 01/1200z 21.8n 68.7w 120 kt
96hr VT 02/1200z 23.5n 72.6w 125 kt
120hr VT 03/1200z 25.5n 76.5w 125 kt

Just for clarification--they are NOT saying that this hurricane is any less of a threat to southern Florida than previously forecast. What they are saying is that the GFDL model forecasts Frances to be less of a threat to southern Florida. I think it is important to note the difference.

GFDL is only ONE model, and it is not in agreement with the other models. I got the impression, by you highliting that threat statement, that you are trying to give the impression that Frances is somehow less of a threat to southern Florida. I'm not sure that is wise, because that is not, in fact, what the NHC is saying in this latest statement.

[Guest]

forecast positions and Max winds

initial 29/1500z 18.6n 54.7w 115 kt
12hr VT 30/0000z 18.8n 56.1w 120 kt
24hr VT 30/1200z 19.5n 58.5w 120 kt
36hr VT 31/0000z 20.0n 61.0w 120 kt
48hr VT 31/1200z 20.5n 63.5w 120 kt
72hr VT 01/1200z 21.8n 68.7w 120 kt
96hr VT 02/1200z 23.5n 72.6w 125 kt
120hr VT 03/1200z 25.5n 76.5w 125 kt

Well judging by those foercast positions it appears with each advisory that the threat is lessening for this area.

[B-Bear]

forecast positions and Max winds

initial 29/1500z 18.6n 54.7w 115 kt
12hr VT 30/0000z 18.8n 56.1w 120 kt
24hr VT 30/1200z 19.5n 58.5w 120 kt
36hr VT 31/0000z 20.0n 61.0w 120 kt
48hr VT 31/1200z 20.5n 63.5w 120 kt
72hr VT 01/1200z 21.8n 68.7w 120 kt
96hr VT 02/1200z 23.5n 72.6w 125 kt
120hr VT 03/1200z 25.5n 76.5w 125 kt

Well judging by those foercast positions it appears with each advisory that the threat is lessening for this area.

Compare those forecast positions to the 5 AM, and then to yesterday's forecast positions, and then to the day before that. It is WAY to early to be suggesting that today's forecast is going to bear out. This hurricane is still 5 days out, and major changes to track are yet likely in the future.

[Brent]

While I do agree that the track shows a LITTLE less threat to Miami/Dade County, just remember the average 5-day track error is 200-300 miles.