8/27/04 FCST: Frances (Atlantic)

[Joel Wright]

Yeah looking at it on satellite it looks pretty sheared now from the west. That combined with drier air to the west should hopefully continue to weaken it. I think there's a very good chance it could be down to a cat two by the time it makes landfall. Very good news indeed.

 

[mikegeukes]

Frances 120 mph winds and pressure is 954 mb.

THE INTENSITY FORECAST IS VERY PROBLEMATIC.

HURRICANE FRANCES DISCUSSION NUMBER 38 5AM EDT
http://www.nhc.noaa.gov/text/refresh/MIATC...ml/030856.shtml?

I found some more links for real time data:

Tropical Cyclones
http://cimss.ssec.wisc.edu/tropic/

Layer Mean Wind Analyses
http://cimss.ssec.wisc.edu/tropic/real-tim.../winds-dlm.html

Saharan Air Layer Analysis
http://cimss.ssec.wisc.edu/tropic/real-tim...ak/sal-atl.html

Satellite Derived Winds and Analyses
http://cimss.ssec.wisc.edu/tropic/real-tim...inds/winds.html

Satellite Images (GOES-12)
http://cimss.ssec.wisc.edu/tropic/real-tim...ges/images.html

24-hour Wind Shear Tendency Analyses
http://cimss.ssec.wisc.edu/tropic/real-tim.../winds-sht.html

Mike

 

[Thomas Loades]

The NHC's forecast still seems to think, though, that by 1400 EDT on Sep. 4, Frances' sustained winds will be back up to 120 kts. with gusts of 145 kts. (132 mph sustain/160 mph gust). That still sounds more than bad enough.

However — and the dynamics may not be the same fo a hurricane as large as Frances — I do recall that Andrew weakened after passing over the Bahamas; the sustained winds went down to 115 mph. But then we know what happened later.

It looks like there's still some convection in the eyewall, from the latest IR image — mostly in the western half of it.

 

[David Schuttler]

Now with the slow down can Florida handle the heavier accumalation of rainfall that will happen?

20 plus inches was one est. I heard

 

[Kevin Scharfenberg]

Is Frances any more than a cat. 1 hurricane right now? The max flight level winds and satellite images barely support hurricane strength. Something appears to be disrupting the circulation so much that it may not recover. I would not be surprised at this rate if Frances is only a tropical storm when it finally reaches the coast. I think NHC really needs to think about backpeddling before they lose more credibility...sticking with cat. 3 strength when the hurricane clearly isn't even producing cat. 3 gusts is not good for anybody.

Edit: I see the 100 mph sustained wind in Eleuthera. That's the first time I've seen surface sustained winds higher than any of the reported flight level winds. Strange!

 

[Jeff Snyder]

I agree with Kevin... I think the max flight-level winds over the last 12-18 hours has been, at most, 105kts. I mean, the discussion itself said that recon and dropsonde measurements don't support the 105kts given, but its based solely on satellite estimates... Why? This has been the case the past 24-36 hours too... The eye was sampled well by one surface station (one of the islands, I forget which one) and only got max sustained winds of 120mph, while the NHC was givin' it 145mph. Ground/plane truth seems to be semi-considerably under satellite "estimates", so I'm not sure why the NHC is basing the 5am intensity soley off these estimates. I tihnk there are some significant politics going on right now, since I"m sure, from a funding standpoint, that it's better to forecast 145mph and get 115mph than to forecast 115mph and get 145mph...

The pressure continues to rise, as it's now (per 8am interm discussion) at 957. Frances is likely a Cat 2 storm right now -- officially still a Cat 3-- and continues to weaken. Satellite presentation is not very good, as the storm continues to become more asymmetric. Again, intensity forecasting for strong hurricanes is a crapshoot, so who know what'll happen in 36 hours. It is interesting to note that strong winds are occurring a long way from the eye, too...

 

[B Ozanne]

As noted above, Andrew reached it's peak intensity before weakening over the Bahamas. Pressure rose to 951mb and winds dropped to 110kts. Upon entering the Florida Straits it rapidly intensified and continued to intensify inland. The most intense convection, lowest pressure, and highest winds occured after the eye had come ashore.

Then again, past performance is no indication of the future.

 

[rdale]

Looks like dropsondes are finding eyewall surface winds around 90-100kts as of 13Z - I can imagine if she doesn't get going before landfall some extended forecasts for the eastern third of the country will be making dramatic changes!

- Rob

 

[B Ozanne]

I'm watching ZNS Network in the Bahamas. At 10:30 am Governors Harbor reported 110mph winds (who knows how accurate that is) and the anchor said the worst was yet to come. Expecting 150mph winds by 2pm. Who knows.

 

[David Wolfson]

That sounds about right. The eye was passing just east of there. I think they've seen about the worst.

 

[Glen Romine]

Models are starting to diverge again on the forecast track. A left turn is pretty much required at this point for Frances to meet the expected NHC forecast track. Looking at the latest sat loop, I'm not sure that Frances isn't already a bit right of the forecast track. With the strength of the high pressure to the north, seems Frances is keeping stronger low-level winds in the tighter presure gradient on the north side - but becoming increasingly assymetric with time. Recent microwave sat images don't show much in the way of precip on the south side of the system. The MIA radar at extended range shows some rather pathetic looking organization, and agrees on a NE shift in the position. I'm leaning towards thinking Frances' landfall will be much further north up the coast - if at all. While this would be good news for those no longer in the path - it would be disastrous for the NWS and FL EM personnel following the historic evacuation.

Glen

 

[B Ozanne]

I wouldn't be that concerned how the storm looks on Miami radar. For one, the radar is currently down. Two, at that range the radar is looking very high into the sky.

From the looks of it forward motion has really slowed. I am less certain about the track now then I was a day ago. I'm not sure what's worse. Two hours of 145 mph winds or ten hours of 100 mph winds.

 

[rdale]

And note that Charley made landfall with sustained 100kt winds as Frances is going to have as per the latest NHC outlook...

- Rob

 

[Glen Romine]

I wouldn't be that concerned how the storm looks on Miami radar. For one, the radar is currently down. Two, at that range the radar is looking very high into the sky.

I know the radar is down, thanks, but the last images are still relavent - the hurricane is not moving very fast. Also, it basically just agrees with the same information from the microwave sat images. Yes, the radar is slicing high through the eyewall at that range - but the eyewall should have the deepest convection in the hurricane - extending upwards of 16 km - which is certainly reasonable at that range. The convection in the nothern eyewall is evident - but there apparently is no deep convection in the southern half of the eyewall. If the radar can see 1/2 the eyewall perpendicular to the radar beam, it should be able to see the other half if it was there and deep enough. It can't.

Glen

 

[Glen Romine]

And note that Charley made landfall with sustained 100kt winds as Frances is going to have as per the latest NHC outlook...

- Rob

Sure, Charley strengthened considerably before landfall - but it was never as disorganized as Frances currently is. While the shear is forecast to weaken just before landfall, and certainly could allow Frances to reintensify - it has steadily weakened for the past day (filling ~ 20 mb) and is under the same detrimental conditions for another 24-36 hours - so what quality of storm will be present when the environmental conditions do finally improve? Obviously nobody knows what is going to actually happen - but it is reasonable to speculate that this storm is dying and may have more of a flooding impact than strong winds.

Glen