Subject: Re: Offshore vs nearshore sonde composite
Date: Tue, 06 Aug 2002 06:17:12 -0800
From: "Christopher Landsea" <Chris.Landsea@noaa.gov>
To: James Franklin <James.Franklin@noaa.gov>
CC: Peter Black <Peter.Black@noaa.gov>,
     Colin McAdie <Colin.J.Mcadie@noaa.gov>,
     Ed Rappaport <Edward.N.Rappaport@noaa.gov>,
     Richard Pasch <Richard.J.Pasch@noaa.gov>,
     John L Beven <John.L.Beven@noaa.gov>,
     "James M. Gross" <James.M.Gross@noaa.gov>,
     Brian R Jarvinen <Brian.R.Jarvinen@noaa.gov>,
     Mark Powell <Mark.Powell@noaa.gov>,
     Max Mayfield <Max.Mayfield@noaa.gov>

Hi James & company,

----- Original Message -----
From: James Franklin <James.Franklin@noaa.gov>
Date: Sunday, August 4, 2002 10:57 am
Subject: Re: Offshore vs nearshore sonde composite

> By the way, the definition of intensity has no mention of land in
> it, so one need not, indeed, should not, be trying to convert actual
> surface winds occurring over one surface to some other surface for
> the purpose of estimating the intensity.  As desirable as this might
> be for certain applications, that simply is not part of the
> definition at this time.  The intensity of a tropical cyclone is the
> maximum sustained wind present at 10 m at a particular point in time
> and attributable to the cyclone circulation.The underlying surface
> can be water, land, or crazy glue, for that matter -
> whatever the hurricane happens to be over at the time.

Yes, that is the definition of intensity that is done operationally,
in the best track, and in the hurricane specialists' table
in their TC reports.  But there also is a requirement at NHC to
estimate what the Saffir-Simpson scale IMPACT was for hurricanes
making landfall in the U.S. or close calls that caused hurricane
conditions over land.  This is needed in the US vulnerability
assessments and is included in HURDAT as the last line for each
storm (e.g. "CFL4" means Category 4 impact in Southeast Florida).
(For example, Hurricane Irene of 1999 is in the best track as
a hurricane throughout its trek over south Florida, yet it is
only listed as a US hurricane impact for Southwest Florida [the
Keys] and not Southeast Florida.  The reasoning being - correct in
my opinion - that the hurricane winds remained offshore and no
sustained hurricane force conditions were observed on the coast or
inland in Miami-Dade or Broward counties.)

I'm not sure if Colin or Ed have a formal definition for the
landfall impact, but here is mine:

HURRICANE LANDFALL IMPACT IN THE CONTINENTAL U.S.:  The highest maximum
sustained [1 min] wind present at 10 m at the U.S. coast or inland
attributable to the cyclone circulation as the hurricane is making
landfall (or a close approach).  This highest wind is used to
assign the appropriate Saffir-Simpson Hurricane Scale category.

THIS is the value that the Andrew debate really centers on now...

Best regards,
chris

Chris Landsea
NOAA AOML/Hurricane Research Division