Tropical Storm Grace Post-Storm Analysis

[JonathanBelles]

When do you think Grace really formed?? When do you think it became a Tropical Storm?

Please provide proof for all statements made in this thread.

[CrazyC83]

Based on the structure and environment, I believe it formed at 0000Z on October 1.

[Cryomaniac]

More pressing, when did it lose all of it's tropical characteristics?

[CrazyC83]

More pressing, when did it lose all of it's tropical characteristics?

I believe it was at 0000Z October 7, while over Great Britain. It still appeared to be warm-core and non-frontal as it approached and made landfall.

[Cryomaniac]

More pressing, when did it lose all of it's tropical characteristics?

I believe it was at 0000Z October 7, while over Great Britain. It still appeared to be warm-core and non-frontal as it approached and made landfall.

I agree, but I'm sure the NHC wont.

[Chacor]

Grace appeared to keep its structure well-defined with a banding ring of convection as far over land as into eastern Wales/southwest England, which makes this an interesting TCR to watch for.

[cycloneye]

I think the Grace report be one of the last or the last one to be out. Will they upgrade to hurricane?

[Ad Novoxium]

I think in terms of intensity, it will be given the "go" for Hurricane, largely because A) it had the structure and organization, and B) they've upgraded based on less (the original quote on Vince was that "if it looks like a hurricane, it probably is"). However, I know little about what truly makes systems tropical, extratropical, and subtropical, so on the matter of when it formed and when it transformed, I can't truly say.

[Derek Ortt]

I do not expect an upgrade from Grace. Just no conclusive data to justify the upgrade

[Cryomaniac]

I do not expect an upgrade from Grace. Just no conclusive data to justify the upgrade

Do you think it was still at least partly tropical at landfall?

[Ad Novoxium]

I do not expect an upgrade from Grace. Just no conclusive data to justify the upgrade

I wonder something: Is there a difference between no conclusive data signifying an upgrade and a lack of data in terms of making a post-season upgrade (Grace was fairly far out to sea)? I ask because something similar occured in 01 when Barry very nearly got to hurricane intensity at landfall.

[Derek Ortt]

no data and inconclusive data are basically the same thing. It is still inconclusive and cannot really justify an upgrade

[CrazyC83]

There isn't much data period from Grace. The only knowns are:

1/1800 - Pressure was 984mb based on a surface report from the Azores - there were no conclusive wind reports at all. That was at the first instance the eye was well-defined. After that, it clearly weakened, likely dropping to about 40 kt around 2/1200 and at which point it was pretty steady-state until about 3/1800.

6/0000 - Pressure was 986mb based on a ship report, although at that point the winds were no more than 50 kt and the storm looked a lot better between 4/1200 and 5/1800.

6/1800 to 7/0000 - Ship reports I believe suggested 35 kt winds at that time, and pressure at landfall appeared to have been 995mb based on surface observations. From how I could interpret satellites, Grace appeared distinct and tropical until about 6/2100. Around 7/0000, it rapidly lost its convection and by 7/0600 it was clearly nothing more than part of the frontal zone.

Lowest pressure was probably at around 5/0600 or 5/1200 and was likely around 981mb based on extrapolation from the peak to the 986 and how much it decayed in between. As for the winds, a lot of guessing has to be done. Normally, 981mb = about 75 kt, but at such a high latitude the normal pressure-wind relationship certainly does not apply, even for a small storm like Grace.