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Comments of and replies to the
National Hurricane Center Best-Track Change Committee
February 2004


Minutes of the best-track change committee meeting, 23 February, 2004
Members Jack Beven, Jim Gross, Brian Jarvinen, Richard Pasch, Ed Rappaport, 
and chair (Colin McAdie) present.					

   < Replies to NHC Best Track Change Committee indented and in brackets -
     CWL - March 2004 >

The committee met to consider the third revision submitted by Chris Landsea 
et al. for the period 1851-1910, received 12 Dec 2003.    The committee 
delayed meeting for several weeks, by mutual agreement, so that Landsea et 
al. could obtain additional observations from Bermuda that might have 
bearing on the storms of 1891. 

General comments:
There seems to be a wealth of data available from the Army forts in Texas.   
The committee would appreciate knowing the period during which this data is 
available, and encourages its use in any future reanalysis.

   < The Army fort data has been utilized for reconstructing hurricane
     impacts since at least David Ludlum's _Early American Hurricanes
     1492-1870_.  The vast majority of these observations were collected
     between the early 1850s and the early 1890s.  (1890 was the first
     year of the establishment of the U.S. Weather Bureau as a civilian
     group.)  It has only been in the last two years though that it has
     been easy to access these documents through the efforts of the
     National Climatic Data Center's program - Climate Database Modernization 
     Program - .  This
     project has scanned in to electronic format thousands of such original
     documents and allows their access on-line.  It is suggested that the
     availablility of these observations should at some point lead to a
     thorough re-study of the Atlantic basin hurricane database for the
     period of the 1850s through the 1880s.  Unfortunately, such a project
     is beyond the scope of the current re-analysis efforts. >

Model results provided by Mike Dickinson are mentioned without elaboration.   
The committee would appreciate some documentation on the model mentioned in 
the metadata.

   < The model employed by Mike Dickinson is the Accurate Environmental
     Forecasting (AEF) RealTrack model, which is based upon the operational
     Geophysical Fluid Dynamics Laboratory hurricane forecast model.  The
     AEF RealTrack model is a version that has been extensively modified to
     permit simulations of the wind field produced by a hurricane with a
     prescribed track and intensity.  Dickinson et al. (2004) will be 
     presented at the May 2004 AMS Hurricanes and Tropical Meteorology
     Conference.  This paper is now specifically referenced in the metadata
     writeup and is provided here as an appendix. >
 
For convenience, the following is organized by year and storm number.

Specific comments: 
1851 #1 Accepted as revised.  Note that Hydrological Prediction Center should
be Hydrometeorological Prediction Center. 

   < So changed. >

1854 #1 Additional storm is accepted, however it is noted that the winds may 
be a little high given the Ft. Ringgold pressure.  Noted that Ft. Ringgold is 
inland.   

   < Agreed.  Winds reduced from 60 kt as originally estimated down to
     50 kt at 18 UTC on the 26th. >


1855 #5 The committee examined a magnified image of the track in the location 
of landfall.   Based on the ensuing discussion concerning the terrain, a 
smoother intensity change results if the 09/16 06 UTC wind is revised to 
105 kt rather than 110 kt. Otherwise accepted. 

   < While a 105 kt intensity estimate at 06 UTC on the 16th might make 
     for a smoother intensity time series, the standard for intensity 
     increments for 1851 through 1885 has been 10 kt.  Thus all 239 
     tropical storms and hurricanes added into HURDAT for this early era
     have a 10 kt resolution to their intensity estimates.  Making an
     exception for this particular system would not be advisable since
     there really is not enough evidence for knowing the intensity to
     the nearest 5 kt at either 105 or 110 kt.  (The error for this system 
     is probably more like plus or minus 10-15 kt at landfall.)  Thus the 
     intensity is kept at 110 kt for this time. >

1878 #5 The revision is accepted on the basis of reinterpretation of the 
4-cup anemometer data.  The use of the Dickinson model in this case is not 
completely clear.   Please discuss.  Although accepted, the committee feels 
it would be more  comprehensive to corroborate with any possible data between 
Cape Lookout and Myrtle Beach.

   < The model employed by Mike Dickinson is the Accurate Environmental
     Forecasting (AEF) RealTrack model, which is based upon the operational
     Geophysical Fluid Dynamics Laboratory hurricane forecast model.  The
     AEF RealTrack model is a version that has been extensively modified to
     permit simulations of the wind field produced by a hurricane with a
     prescribed track and intensity.  Dickinson et al. (2004) will be 
     presented at the May 2004 AMS Hurricanes and Tropical Meteorology
     Conference.  This paper is now specifically referenced in the metadata
     writeup and is provided here as an appendix. 

     There were three additional observations available between Myrtle Beach, 
     SC and Cape Lookout, NC:  Smithville, NC (now Southport) - SE 42 kt, 
     Wilmington, NC - SE 26 kt, Sloop Point, NC (northeast of Wilmington
     near Top Sail Beach) - 55 kt (estimated), and Cape Lookout.  Thus
     the other measurements are also consistent with tropical storm
     conditions in North Carolina.  These are now also added to the metadata 
     writeup. >

1891 #7 #8 #9   The analysis and data were examined and discussed at length. 
The track of (new) storm #7 is accepted as revised.   It is not clear, 
however, from the analysis provided that storm #8 can be completely 
eliminated from the Caribbean.  It is plausible, based on the analysis, that 
a weak tropical system (#8) may have existed in the Caribbean, drifted 
northward,  and served as the impetus for the formation of the extratropical 
low over Florida.   It seems somewhat unlikely that a purely baroclinic low 
would have developed this early, this far south.  In this scenario, #8 (with a
revised track to fit the analysis) becomes extratropical over Florida, and 
accounts for the northeastward portion of the track of #9.   (Inclusion of the
track of the extratropical portion of the track is consistent with current 
practice.)  The committee is in general agreement that #9 probably did not 
exist, given lack of discussion in MWR and the data presented, however Jack 
Beven has offered a final attempt to find anything that might have 
contributed to the Mitchell track.   It is still somewhat disconcerting that 
a track (Mitchells) would be published based on pure speculation. (concerning 
this please see the addendum)

   < Agreed.  Storm #9 has been removed and storms #7 and #8 have been
     kept with #8 revised as recommended.  Storm #8 is retained, but as
     indicated in the metadata file, the evidence for it being of tropical
     storm intensity as a tropical cyclone is marginal. >

1891 additional system #1 (July) Agree with not adding this system.

1891 additional system #4 (Sept) Agree with not adding this system.

1898 #8 Thank you for the additional research on this system.  The track is 
accepted, although it is noted that the northeastward motion, given the track
of #7, still seems unlikely.  It is not clear how to resolve the apparent 
inconsistency with the data supporting the track of #8.  The committee would 
appreciate plots of the data.  

   < The worksheets that we utilized for plotting up the data are now
     provided.  See appendix. > 

1898 additional system (May)   Agree with not adding this system.

1903 additional system #1 Agree with not adding this system.

1907 additional system #1 Agree with not adding this system, although Jack 
Beven will investigate further as time permits. 

1908 additional system #2 Accepted.  Note apparent typo with pressure of 
1990 mb.

   < Typo corrected.  1990 mb changed to the correct 990 mb. >
 
Note: inserted as an addendum to the minutes of 23 February 2004.

Subject: Re: BTC - minutes
Date: Wed, 25 Feb 2004 12:37:51 -0500
From: "John L Beven" 
Organization: Tropical Prediction Center/National Hurricane Center
To: Colin.J.McAdie@noaa.gov
CC: "Edward.N.Rappaport" ,
     "James.M.Gross" ,
     "Richard.J.Pasch" ,
     "Brian.R.Jarvinen" 

Colin, Ed, and all,

   As a follow up to my message yesterday, I did more library research
and found the publications of Vines, Garriott, and Fassig that Mitchell 
referenced in his 1924 publication.

   The tracks for October 1891 shown by Garriott and Fassig are rather
different than those in Mitchell.  First, neither Garriott or Fassig show 
the track of storm 7, even though it is fairly well documented in the Monthly 
Weather Review.  Second, Garriott and Fassig both start the track of storm 8 
over the eastern Gulf of Mexico two days after Chris' data shows storm 7 has 
gone by.  Third, neither Garriott or Fassig show a storm with a track even
remotely resembling that of storm 9.

   It is in Mitchell that storm 7 gets added to the tracks, that storm 8
gets extended into the Caribbean, and that storm 9 is added to the tracks.

   Father Vines 1898 work that was referenced in Mitchell makes no
mention of any tropical cyclone in Cuba in 1891.  Neither does a spanish-
language pamphlet on tropical cyclones affecting Cuba.  This suggests that, 
at best, storms 7 and 8 were weak systems if and when they affected the 
island.

   One caveat to all of this is that Mitchell, Fassig, and Garriott all
seemed to be interested in stronger and more easily trackable cyclones, so it 
is possible that the weaker systems may not been as well handled.

Jack


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