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Fort.22 file

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A single meteorological input file (wind velocity and atmospheric pressure) is read when meteorological forcing has been indicated by the NWS parameter in the fort.15 file. More precisely, the format of and need for the fort.22 file depend on the ones and tens (i.e. the last 2) digits and the sign (positive/negative) of NWS (see here). See also the Supplemental Meteorological/Wave/Ice Parameters and wind stress pages.

Contents

General Notes

Unless otherwise specified for a given format, ADCIRC expects wind data to represent specific conditions and pressure data to be sea level pressure. Where necessary, ADCIRC assumes a "background" atmospheric pressure of 1013 millibars.

Meteorological data in most formats must be provided for the entire model run, otherwise the run will crash. Exceptions include OWI (NWS=12) and GFDL (NWS=16).

For most formats, latitude and longitude coordinates describing the spatial extents of the meteorological data must follow the convention of the ADCIRC model domain. For example, if the mesh uses negative longitude values to indicate locations West of the Greenwich meridian, the meteorological file must be similarly organized. Any grid that crosses the Greenwich Meridian should be organized so that the seam occurs at 180 deg longitude. Therefore, the meteorological and ADCIRC grids should use negative longitudes West of the Greenwich Meridian and positive longitudes to the East.

File Format

The remainder of this page is devoted to the formats of the fort.22 file for the different values of NWS. Each line of input data is represented by a line containing the input variable name(s). Blank lines are only to enhance readability. Loops indicate multiple lines of input. Conditional input is indicated by an if clause.

NWS = 1 Wind Stress & Pressure at All Nodes and Timesteps

File Structure

for k=1,NP

JN, WSX(k), WSY(k), PRN(k,j)

end k loop

Notes

Meteorological data is input directly to all nodes in the ADCIRC grid.

The units for pressure are meters of water.

The first set of met. data corresponds to TIME=STATIM+DTDP. Additional sets of met data must be provided at every time step, (WTIMINC = DTDP).

Wind stress must be input in units of velocity squared (consistent with the units of gravity) and surface atmospheric pressure must be input in units of equivalent height of water (e.g., meters of water, feet of water that are consistent with the units of gravity). Stress in these units is obtained by dividing stress in units of force/area by the reference density of water. Pressure in these units is obtained by dividing pressure in units of force/area by the gravitational constant and the reference density of water. For example, 10^5Pa =10^5 N/m^2 =10^5 kg m/(s m)^2 divided by 9.81 m/s^2 and 10^3 kg/m^3 equals 10.2 meters of water.

NWS = ±2 Wind Stress & Pressure at All Nodes and Specified Time Interval

File Structure

for k=1, NP

JN, WSX(k), WSY(k), PRN(k,j)

end k loop

Notes

Meteorological data is input directly to all nodes in the ADCIRC grid.

The units for pressure are meters of H2O.

If NWS=2, the first set of met. data corresponds to TIME=STATIM. If NWS=-2, the first set of met data corresponds to TIME=HOT START TIME. Additional sets of met. data must be provided every WTIMINC, where WTIMINC is the met. data time interval and is specified in the Model Parameter and Periodic Boundary Condition File. Met data is interpolated in time to the ADCIRC time step.

Wind stress must be input in units of velocity squared (consistent with the units of gravity) and surface atmospheric pressure must be input in units of equivalent height of water (e.g., meters of water, feet of water that are consistent with the units of gravity).Stress in these units is obtained by dividing stress in units of force/area by the reference density of water. Pressure in these units is obtained by dividing pressure in units of force/area by the gravitational constant and the reference density of water. For example,

10^5Pa =10^5 N/m^2 =10^5 kg m/(s m)^2 divided by 9.81 m/s^2 and 10^3 kg/m^3 equals 10.2 meters of water

NWS = 3 Fleet Numeric Format

File Structure

IWTIME

for k = 1,NWLAT

for j = 1,NWLON
WSPEED(k,j)
end j loop

end k loop

for k = 1, NWLAT

for j = 1, NWLON
WDIR(k,j)
end j loop

end k loop


Notes

Meteorological data is input to a longitude, latitude grid and interpolated in space onto the ADCIRC grid.The ADCIRC grid must be in lon, lat coordinates.

The first set of met. data must be at or before the date and time listed in the Model Parameter and Periodic Boundary Condition File as the beginning time of the simulation. Additional sets of met. data must be provided every WTIMINC, where WTIMINC is the met. data time interval.Values for NWLAT, NWLON, WTIMINC, and several other parameters must be set in the Model Parameter and Periodic Boundary Condition File. Met data is interpolated in time to the ADCIRC time step.

Wind velocity (@ 10 m above the water surface) must be input in units of m/s (regardless of the units of gravity).

The following relations are used to compute wind stress from the input wind velocity.

WIND_SPEED = magnitude of WIND_VEL

DRAG_COEFF = 0.001*(0.75+0.067*WIND_SPEED)

If (DRAG_COEFF.gt.0.003) DRAG_COEFF=0.003

WIND_STRESS = DRAG_COEFF*0.001293*WIND_VEL*WIND_SPEED

NWS = ±4 PBL Hurricane Model format

Meteorological data is input directly to a subset of nodes in the ADCIRC grid (as specified by the node number JN).The ADCIRC grid must be either in lon, lat coordinates or in meter-based Cartesian coordinates.

File Structure

FOR EACH WIND TIME INCREMENT

DO UNTIL LINE = ” #”
JN, WVNX(JN), WVNY(JN), PRN(k,j)
END DO UNTIL

END FOR EACH

Notes

If NWS = 4, the first set of met. data corresponds to TIME=STATIM. If NWS = -4, the first set of met data corresponds to TIME=HOT START TIME. Additional sets of met. data must be provided every WTIMINC, where WTIMINC is the met. data time interval and is specified in the Model Parameter and Periodic Boundary Condition File. Met data is interpolated in time to the ADCIRC time step.

Each data line must have the format I8, 3E13.5. Data input lines are repeated for as many nodes as desired. A line containing the # symbol in column 2 indicates met data at the next time increment begins on the following line. At each new time, any node that is not specified in the input file is assumed to have zero wind velocity and pressure = 1013.

Wind velocity (assumed to be 10m 10 minute averaged value) must be input in knots and surface atmospheric pressure must be input in hundredths of a millibar.

The following relations are used to compute wind stress from wind velocity:

WIND_VEL{m/s @ 10m} = WIND_VEL{knots @ bl average}*0.5144 (In prior ADCIRC versions, an additional factor of 1.04 was included in the formulation to convert from 30 minute avg winds to 10 minute avg winds. This factor was removed and it is currently assumed that the input wind data uses a 10 minute averaging period. Note, this is unrelated to the value of WTIMINC).

WIND_SPEED = magnitude of WIND_VEL

DRAG_COEFF = 0.001*(0.75+0.067*WIND_SPEED)

if(DRAG_COEFF.gt.0.003) DRAG_COEFF=0.003

WIND_STRESS = DRAG_COEFF*0.001293*WIND_VEL*WIND_SPEED

The following relationship is used in ADCIRC to convert to pressure in meters of water from pressure in hundredths of a millibar:

PRESSURE{m H2O}=PRESSURE{Pa/100}*100/(GRAVITY*DENSITY H2O)

NWS = ±5 Wind Velocity & Pressure at All Nodes and Specified Time Interval

File Structure

for k = 1, NP

JN, WVX(k), WVY(k), PRN(k,j)

end k loop

Notes

Meteorological data is input directly to all nodes in the ADCIRC grid.The ADCIRC grid must be either in lon, lat coordinates or in meter-based Cartesian coordinates.

If NWS=5, the first set of met. data corresponds to TIME=STATIM. If NWS=-5, the first set of met data corresponds to TIME=HOT START TIME. Additional sets of met. data must be provided every WTIMINC, where WTIMINC is the met. data time interval and is specified in the Model Parameter and Periodic Boundary Condition File. Met data is interpolated in time to the ADCIRC time step.

Wind velocity (@ 10 m above the water surface) must be input in m/s and surface atmospheric pressure must be input in meters of water.

The following relations are used to compute wind stress from wind velocity:

WIND_SPEED = magnitude of WIND_VEL

DRAG_COEFF = 0.001*(0.75+0.067*WIND_SPEED)

if(DRAG_COEFF.gt.0.003) DRAG_COEFF=0.003

WIND_STRESS = DRAG_COEFF*0.001293*WIND_VEL*WIND_SPEED

NWS = 6 Wind Velocity and Pressure on Rectangular Grid

File Structure

for k=1, NWLAT

for j=1, NWLON
WVXFN(k,j), WVYFN(k,j), PRN(k,j)
end j loop

end k loop

Notes

In versions 43 and earlier the format of input was P, U, V. The input has now changed to U, V, P to be consistent with other NWS formats.

Meteorological data is input on a rectangular grid (either in Longitude, Latitude or Cartesian coordinates, consistent with the grid coordinates) and interpolated in space onto the ADCIRC grid. In setting up the meteorological grid it is assumed that y (e.g., latitude) varies from north (k=1) to south (k=NWLAT) and x (e.g., longitude) varies from west (j=1) to east (j=NWLON). The spatial extents of the meteorological grid must be consistent with the ADCIRC model domain. For example, if ADCIRC uses negative longitude values to indicate locations W of the Greenwich meridian, the meteorological file must be similarly organized. Any grid that crosses the Greenwich Meridian should be organized so that the seam occurs @ 180 deg longitude. Therefore, the meteorological and ADCIRC grids should use negative longitudes W of the Greenwich Meridian and positive longitudes to the E.

The meteorological grid MUST cover the entire ADCIRC mesh; that is, the ADCIRC mesh must be entirely within the meteorological grid or an error will result.

The first set of met. data corresponds to the beginning time of the current simulation. If the model is cold started this corresponds to TIME=STATIM . If the model is hot started, this corresponds to TIME=HOT START TIME. Additional sets of met. data must be provided every WTIMINC, where WTIMINC is the met. data time interval.Values for NWLAT, NWLON, WTIMINC, and several other parameters must be set in the fort.15 file. Met data is interpolated in time to the ADCIRC time step.

Wind velocity (@ 10 m above the water surface) must be input in units of m/s and surface atmospheric pressure must be input in units of Pascals = Newtons/square meter.

The following relations are used to compute wind stress from the input wind velocity.

WIND_SPEED = magnitude of WIND_VEL

DRAG_COEFF = 0.001*(0.75+0.067*WIND_SPEED)

If (DRAG_COEFF.gt.0.003) DRAG_COEFF=0.003

WIND_STRESS = DRAG_COEFF*0.001293*WIND_VEL*WIND_SPEED

The following relationship is used in ADCIRC to convert to pressure in meters of water from pressure in Pascal:

PRESSURE{m H2O}=PRESSURE{Pascal}/(GRAVITY*DENSITY H2O)

NWS = ±7 Wind Stress and Pressure on Rectangular Grid

This format has not been fully implemented, though it is expected in v55.

ADCIRC version:  ?55?


File Structure

for k=1, NWLAT

for j=1, NWLON
WVXFN(K,J),WVYFN(K,J),PRN(K,J)
END DO

END DO

Notes

NWS = ±8 (Symmetric) Dynamic Holland Vortex Model

File Structure

Use the ATCF Best Track/Objective Aid/Wind Radii Format.

Notes

Hurricane parameters are read in from the Single File Meteorological Forcing Input File. Wind velocity and atmospheric pressure are calculated at every node on the fly by ADCIRC internally using the Dynamic Holland model. The input file is fixed width (not comma separated values or csv) and is assumed to correspond to the ATCF Best Track/Objective Aid/Wind Radii Format. Historical tracks, real-time hindcast tracks and real-time forecast tracks may be found in this format. Selecting NWS = 8 also requires the specification of the cold start time, storm number, and boundary layer adjustment (see YYYY MM DD HH24 StormNumber BLAdj). Garret’s formula is used to compute wind stress from the wind velocity.

The symmetric vortex model (NWS=8) in ADCIRC assumes that the longitudes in the fort.22 are west longitude, so it multiplies the longitude values by -1. It ignores the ‘E’ or ‘W’ in the longitude column of the fort.22.

The symmetric vortex model (NWS=8) does not use any of the isotach wind speeds or wind radii data. When reading lines labeled “BEST” from the fort.22, it obtains timing information from the year, month, day, and hour in column 3. When reading lines labeled “OFCL” from the fort.22, it uses the forecast increment (a.k.a. TAU) from column 6. The use of these two different columns by ADCIRC NWS=8 is to maintain consistency with the official file structure for the ATCF file format.

For NWS=8, ADCIRC knows the current time because the user provides the year, month, day, and hour of cold start on the WTIMINC line in your fort.15. It also has the time that has elapsed since cold start, because that is provided in the hotstart file, if any. It then compares the current time with the date/times in the fort.22 (as described in the previous paragraph) to automatically find the right place to begin reading data from the fort.22.

So, in summary, if the whole fort.22 consists of “BEST” lines, the symmetric vortex model (NWS=8) only looks at column 3 for time information. And it automatically knows where to start reading cyclone data, based on the coldstart date/time the user provides in the fort.15 file.

NWS = 9 Asymmetric Holland Vortex Model

This has been deprecated and is no longer available.

ADCIRC version: <  ???


NWS = 10 National Climatic Data Center GFS

It appears there is no fort.22 file for this format, and users should consult the fort.200 page, but this hasn't been confirmed.

Wind velocity and atmospheric pressure are read in from a sequence of National Weather Service (NWS) Aviation (AVN) model output files. Each AVN file is assumed to contain data on a Gaussian longitude, latitude grid at a single time.

File Structure

for k=1, LONB*LATB

PG(k), UG(k), VG(k)

end j loop

NWS = 11 Stripped National Weather Service (NWS) ETA 29km

It appears there is no fort.22 file for this format, and users should consult the fort.200 page, but this hasn't been confirmed.

Wind velocity (10 m) and atmospheric pressure are read in from a sequence of stripped down National Weather Service (NWS) ETA 29km model output files.

File Structure

for k=1, LONB*LATB

PG(k), UG(k), VG(k)

end j loop

NWS = ±12 Oceanweather ASCII Format Gridded Wind and Pressure

Oceanweather Inc (OWI) ASCII "WIN"/"PRE" format , details can be found at NWS12

NWS = 13 Oceanweather NetCDF Format Gridded Wind and Pressure

Oceanweather Inc (OWI) NetCDF format , details can be found at NWS13

ADCIRC version: 55


NWS = ±14 Gridded GRIB2 or NetCDF Wind and Pressure

When using NetCDF files (fort.221.nc, fort.222.nc) as met inputs, the fort.22 is required in order to list the relevant variable names so that the internal NetCDF read routines can find the pertinent variables. In the case of GRIB2 input files (fort.221.grb2, fort.222.grb2) the fort.22 is not required because the variable names are standardized and on start-up the internal wgrb2api library prints out inventory look-up files (*.inv) that it uses to find the information contained within the *.grb2 files.

ADCIRC version: = 55


File Structure

Temporal dimension name
Datetime variable name
Format of the datetime time variable [special note, if first character is not a '%' then it will ignore this variable and will assume to start from the first time snap]
Zonal (east-west) dimension name
Longitude variable name
Meridional (north-south) dimension name
Latitude variable name
Sea-level Pressure variable name
Zonal 10-m Wind Velocity name
Meridional 10-m Wind Velocity name
Ice area-fraction name [optional, only if fort.225.nc present for ice area fraction]

Example (WRF output)

Time
Times [if no datetime variable then set to dummy such as 'none']
%Y-%m-%d_%H:%M:%S [if no datetime variable then set to dummy such as 'none']
west_east
XLONG
south_north
XLAT
PSFC
U10
V10
aice [optional]

Notes

If the time variable is not in a datetime format (e.g., is a float in minutes since..) the datetime format can be set to a dummy name, e.g., 'minutes'. The code checks to see if the first character of the datetime format is '%'. If not the code will assume to simply begin reading from the first time snap. If the datetime variable is available the code will work out which time snap to start reading from based on the reference date, NCDATE located near or at the bottom of the fort.15 file.

NWS = 15 H*Wind Gridded Wind and Inferred Pressure

The goal of the implementation of the HWind capability within ADCIRC was to allow HWind files to be used as-is, without resorting to an intermediate format. As a result, the fort.22 file consists of a header line to provide some configuration parameters, and then a list of the filenames of the HWind files to be used in the ADCIRC run.

File Structure

comment line

hWindMultiplier

presssureWindRelationship

for i=1 to numHWindFiles

hours(i) centralPressure(i) rampMult(i) filename(i)

end i loop

Notes

HWind files are data assimilated snapshots of the wind velocity fields of tropical cyclones that were produced by the NOAA Hurricane Research Division (HRD) through 2013, before becoming a private sector data product. The files have the following characteristics:

the format explicitly indicates the center of the storm

the (u,v) data are on a regular grid

the regular grid is a mercator projection with origin at storm center

the mercator grid spacing is in meters and is uniform in x and y (dx=dy)

the dimensions (nx,ny) of the mercator grid are equal (nx=ny)

the grid dimensions change from snapshot to snapshot; for example, the first shapshot may be 161×161 while the 2nd snapshot may be 121×121 (etc)

sequential hwind snapshots will not be evenly spaced in time for a particular storm

H*Wind data do not contain barometric pressure information. For the dvorak, knaffzehr, and specified Pc options, the barometric pressure field is computed by determining the radius to maximum winds Rmax (i.e., the distance of Vmax from the center of the storm), calculating the Holland B parameter, and then using the Holland formulation to calculate barometric pressure as a function of the distance from the center of the storm.

To illustrate the definitions and descriptions provided, a concrete example of an HWind fort.22 file is provided as follows:

! first line is a comment line, max length 1024 characters

1.0 ! 2nd line is a velocity magnitude multiplier

dvorak ! 3rd line: one word for the pressure-wind relationship

0.0 -1 0.0 “/home/jason/hwind/al092011_0828_1330” ! time (hours), Pc (mb), ramp mult, filename

6.0 -1 0.5 “/home/jason/hwind/al092011_0828_1930”

12.0 -1 1.0 “/home/jason/hwind/al092011_0829_0130”

NWS = 16 ASCII NOAA GFDL Gridded Wind And Pressure

The GFDL input capability uses GFDL model output files as-is; as a result, the fort.22 file consists of a list of GFDL model output files to be used in ADCIRC.

File Structure

comment line

GFDLWindMultplier

MaxExtrapolationDistance

for i=1 to numGFDLFiles

hours(i) rampMult(i) filename(i)

end i loop

Notes

GFDL model output files are produced by the Geophysical Fluid Dynamics Laboratory at NOAA. Each ASCII GFDL model output file contains one or more nested grid dataset where the nested grids are allowed to change in time. Coarse grid data is not stored where finer nest data is given. The files are formatted as follows:

Line 1: Number of grid cells (f10.4) NCELLS

Lines 2 through NCELLS+1: Ten columns of data formatted as 10f10.4 as follows:

column 1: u (m/s)

column 2: v (m/s)

column 3: Temperature (K)

column 4: mixing ratio(kg/kg)

column 5: storm accum precipitation (cm)

column 6: sea level pressure (hPa)

column 7: longitude (decimal deg)

column 8: latitude (decimal deg)

column 9: hurricane hour

column 10: nest number (this is not always present)


To illustrate the definitions and descriptions provided, a concrete example of a GFDL fort.22 file is provided as follows:

! first line is a comment line, max length 1024 characters

1.0 ! 2nd line is a velocity magnitude multiplier

100.0 ! 3rd line: maximum extrapolation distance (m)

0.0 -1 0.0 “/home/jason/hwind/al092011_0828_1330″ ! time (hours), Pc (mb), ramp mult, filename

6.0 -1 0.5 “/home/jason/hwind/al092011_0828_1930″


If the ADCIRC time falls outside the interval of time covered by the GFDL model output files, ADCIRC will insert “blank snaps”, i.e., it will set the wind velocity at all mesh vertices to 0.0 m/s and the barometric pressure to a uniform background pressure of 1013mb.

NWS = 19 Dynamic Asymmetric Holland Vortex Model

Note that use of this is discouraged.

File Structure

The file needs to be in the ATCF Best Track/Objective Aid/Wind Radii Format.

Notes

User has the ability to select which isotach to use in each of the 4 quadrants. User also has ability to modify RMAX and Holland’s B parameter using the ASWIP program. The auxiliary preprocessing program ASWIP.F (located in the /wind directory and executable is created by typing, make aswip, in the work folder after adcirc executable has been generated), will generate the fort.22 input file for NWS=19 from a NWS= 9 formatted input file.

Hurricane parameters are read in from the Single File Meteorological Forcing Input File. It is assumed that the line in the fort.22 file with a zero as the forecast increment (i.e., column 6) corresponds to the start of the current simulation run, whether it is a hotstart or cold start. In other words, there is no option to set the NWS value negative to indicate that the file starts at the ADCIRC hotstart time. Rather, the forecast increment in hours (column 6) is used to indicate the relationship between the ADCIRC time and the data in the fort.22 file. Wind velocity and atmospheric pressure are calculated at exact finite element mesh node locations and directly coupled to ADCIRC at every time step using the asymmetric hurricane vortex formulation (Mattocks et al, 2006; Mattocks and Forbes, 2008) based on the Holland gradient wind model. The input file is assumed to correspond to the ATCF Best Track/Objective Aid/Wind Radii Format. Historical tracks, real-time hindcast tracks and real-time forecast tracks may be found in this format. This option uses the radii at specific wind speeds (34, 50, 64, 100 knots) reported in the four quadrants (NE, SE, SW, NW) of the storm to calculate the radius of maximum winds as a function of the azimuthal angle. Garret’s formula is used to compute wind stress from the wind velocity. The NWS=19 option allows the user to set a value for Rmax and Holland B Parameter. Additionally the user can select the isotachs to be used for each of the 4 quadrants. The utility program aswip_1.0.3.F located in the /wind folder will generate the NWS=19 fomatted file from a NWS=9 formatted fort.22 input file.

In order to use the NWS=19 option, the file needs to be in best track format. The forecast period (column #6) needs to be edited to reflect the time of the forecast/nowcast for each track location (each line) in hours from the start of the simulation (0, 6, 12, 18, etc). The original data in that column depends on what type of best track format data is being used. The original data might have 0 or other numbers in that column. See: ATCF Best Track/Objective Aid/Wind Radii Format. It is suggested that users change the “BEST” tech type to “ASYM” in column 5 in the fort.22 file to denote that the file has been modified to accommodate the asymmetric wind formulation (the simulation time in hours in the 6th column has been added, etc.) so it will not get confused in the future with a best track file.

The NWS=19 option requires the following variables in the fort.22 file in a best track format:

Forecast time in hours (column 6); enter the time in hours in each record starting at 0

Latitude of the eye (column 7)

Longitude of the eye (column 8)

Maximum sustained wind speed in knots (column 9)

Minimum sea level pressure in MB (column 10)

Wind intensity in knots of the radii defined in the record (34, 50, 64 or 100 knots) (column 12)

Radius of specified wind intensity for quadrants 1, 2, 3, 4 in NM (columns 14, 15, 16, 17); ? 0

Background pressure in MB (column 18); a standard value of 1013 can be used

Rmax as reported in the ATCF BEST TRACK file in column 20

Storm Name in Column 28 ATCF file format

Time Record number in column 29. There can be multiple lines for a given time record depending on the number of isotachs reported in the ATCF File

number of isotachs reported in the ATCF file for the corresponding Time record.

Columns 31-34 indicate the selection of radii for that particular isotach. 0 indicates do not use this radius, and 1 indicates use this radius and corresponding wind speed.

Columns 35-38 are the designated Rmax values computed for each of the quadrants selected for each particular isotach.

Column 39 is the Holland B parameter computed using the formulas outlines in the Holland paper, and implemented using the aswip program.

Available files:

The format of the file is fixed and users will want to use the aswip program to be sure that the input fort.22 file is properly formatted.

The command line for NWS=19 is ./aswip -n 19 -m 2 -z 1

NWS = 20 Generalized Asymmetric Holland Vortex Model (GAHM)

File Structure

The file needs is similar to the NWS = 19 format with 8 additional columns of data, see notes below for more information.

Notes

The Generalized Asymmetric Holland Model (GAHM) provides a set of theoretical and practical improvements over previous parametric meteorological vortex models in ADCIRC.

Forecast time in hours (column 6); enter the time in hours in each record starting at 0

Latitude of the eye (column 7)

Longitude of the eye (column 8)

Maximum sustained wind speed in knots (column 9)

Minimum sea level pressure in MB (column 10)

Wind intensity in knots of the radii defined in the record (34, 50, 64 or 100 knots) (column 12)

Radius of specified wind intensity for quadrants 1, 2, 3, 4 in NM (columns 14, 15, 16, 17); ? 0

Background pressure in MB (column 18); a standard value of 1013 can be used

Rmax as reported in the ATCF BEST TRACK file in column 20

Storm Name in Column 28 ATCF file format

Time Record number in column 29. There can be multiple lines for a given time record depending on the number of isotachs reported in the ATCF File

number of isotachs reported in the ATCF file for the corresponding Time record.

Columns 31-34 indicate the selection of radii for that particular isotach. 0 indicates do not use this radius, and 1 indicates use this radius and corresponding wind speed.

Columns 35-38 are the designated Rmax values computed for each of the quadrants selected for each particular isotach.

Column 39 is the Holland B parameter computed using the formulas outlines in the Holland paper, and implemented using the aswip program.

Column 40-43 is the quadrant-varying Holland B parameter

Column 44-47 are the quadrant-varying Vmax calculated at the top of the planetary boundary (a wind reduction factor is applied to reduce the wind speed at the boundary to the 10-m surface)

Historical storm files can be found archived here.

Forecast tracks can be found here.

The format of the file is fixed and users will want to use the aswip program to be sure that the input fort.22 file is properly formatted.

Options for the aswip program using NWS = 20 are the following:

./aswip -n # -m # -z #

-n = nws option
-m = methods of selecting isotachs for use in computation of radius/radii to maximum winds
1: always use the 34kt isotach
2: use the highest available isotach in any quadrant each time
3: use the 50kt isotach if it is available; otherwise use the 34kt isotach
4: use all available isotachs (must choose this for GAHM/NWS=20)
-z = approaches solving for Rmax
1 = only rotate wind vectors afterward
2 = rotate wind vectors before and afterwards (use this for NWS=20)

So the command line for NWS=20 is: ./aswip -n 20 -m 4 -z 2