climate hyperbole

Showing the linearity of the inverse pressure deficit in the cross-section of hurricane Irma

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Naples FLA sea level pressure during hurricane Irma fly-by. NOAA station code NPSF1. The eye of the storm passed directly over Naples, so this station gives a good diametric cross-section of the storm.

Data source: http://www.ndbc.noaa.gov/station_page.php?station=NPSF1

30 inches of Hg was observed to be a typical value of the SLP before the storm hit, thus representing a nominal pressure of the surrounding meteorology. This value was adjusted to 30.1 to remove a slight residual curvature from the inverse pressure anomaly.

Data processing
pre-process data to fix bad time format ( 12:05 am etc ) and extract pressure column:

# copy all data cols to  Irma_naples.txt

awk '($0 ~ /^09/){print}' Irma_naples.txt > Irma_naples_crop.txt

# extract atm pressure col and correct  bogus time formats: "12.xx am"

awk '{if (length($3)==5) dot=3; else dot=2; t=$3;h=int(substr($3,1,dot-1));mm=substr($3,dot,3); \
if (($4=="pm")) add=12; else add=0; if (h==12)h=0; { $3 = h+add "" mm} ;print $1" "$2" "$3" "$12}' Irma_naples_crop.txt > Irma_naples_atm.txt


gnuplot script to recreate graph:

gnuplot>

set xdata time 
set timefmt "%m %d %H:%M"
set datafile missing "-"

set title "Sea Level Pressue at Naples  during Hurricane Irma  ( NOAA NPSF1 station ) "
set xlab "\ndate (mm/dd) \nhttp://www.ndbc.noaa.gov/station_page.php?station=NPSF1" 

set y2lab "inverse presure anomaly / inches Hg^-1"
set ylab "sea level pressure  / inches Hg"
set ytic nomirror ; set y2tics;
set key bottom left Left reverse

 plot "Irma_naples_atm.txt" using 1:4             

 plot "Irma_naples_atm.txt" using 1:4  title "sea level press. ", ""  u 1:((1/(30.1- $4) )) axes x1y2 title "( 1 / ( 30.1- SLP )" linecol rgb "light-blue"