Random Chaos
(Weather Analyst)
Wed Sep 07 2005 02:38 PM
Re: Tropical Storm Ophelia Forms off Florida East Coast

Ophelia:

I'm looking at the models, both intensity and track, and the sat image. Here are my opinions - don't take them as fact - I'm not a pro

Ridge to the north appears to be building. This will force Ophelia to stay south, looping it like the GFS, NOGAPS, and UKMET models show. CMC overweakens the ridge, allowing Ophelia to pass through. I don't see this happening.

Ophelia is showing signs that it is going to strengthen beyond SHIPS guidence. It is already a Dvorak 3.0 - that's just below hurricane strength. Based on this it seems all intensity models are low. GFDL...never even makes Ophelia a TS...clearly wrong. GFDI, GFTI, and GFNI keep Ophelia a TS for 3-4 days before strengthening her to a Cat 2 hurricane in a day...also doesn't seem likely based on what Ophelia has already done. SHIPS and related models bring Ophelia up to a hurricane Cat 1 quickly, but then plateau her and slowly weaken her. While this is possible, given the SSTs and the Sat view, as long as she stay's out to sea I don't see why Ophelia won't grow stronger than Cat 1.

The track is very important to intensity. If Ophelia does this loop that is forcast, it keeps her over warm water longer. The ridge that is forcing the loop is WNW to ESE, which is keeping Ophelia from swinging out to sea, and forcing her south. GFS long term (from NECP's site) takes Ophelia into the Georgia coast and back out over the FL panhandle...the latter point weakened probably to a TD before coming back in over Louisiana. I'm thinking the impact point will be a little further south...into Florida as a Cat 2, and the crossing angle WSW. From there, given a week to allow SSTs to recover from the cooling caused by Katrina, we could see Ophelia reach the gulf as TS and strengthen back to a weak hurricane before swinging north around the ridge after 2+ days.

Lets hope GFDL is correct and weakens this thing. I don't see it happening.

============================

GFDL:

Someone asked about the GFDL and Katrina in the last thread. GFDL was very good on the track and intensity of Katrina only after Katrina became a Hurricane. Before that GFDL just kept insisting on dissipating Katrina, and gave tracks that were widely disparate and erroneous. Becuase of these track issues before Katrina became a hurricane, the southward jog before the Florida landfall was dismissed.

Basically, GFDL seems to need a well established system to build a good track and intensity for. A TS that has been so for at least a day, or a Hurricane. When a system is developing this close to land and this quickly, GFDL often never gets the chance to lock onto it.

GFDL is based on the AVN run from 6 hours before the GFDL comes out (as I recall) combined with biasing information to allow it to lock onto the current storm center. Becuase of this, fast developing systems, like both Katrina was and Ophelia is, are hard for the GFDL to get a good understanding of.

--RC



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