How can I decode the lowest one-minute pressure and peak one-minute winds?

Background:

The Tropical Prediction Center (TPC) has funded the National Data Buoy Center (NDBC) to change the software on their buoys to report the highest one-minute wind and the lowest one-minute pressure observed in the last hour. This will provide improved temporal sampling of key measurements that will more closely match the averaging times of wind and pressure implicit in TPC's forecasts. Selected buoy stations will be deployed with this capability early in the summer of 2005.

The additional information that these buoys will transmit each hour is as follows:

Measurement	Units
Highest one-minute mean wind speed	m/s to nearest m/s
Direction of one-minute peak wind	nearest ten degrees
Time of one-minute peak wind	nearest minute
Lowest one-minute average pressure	nearest 0.1 hPa
Time of one-minute pressure	nearest minute

Because of power system constraints the barometer cannot be left on continuously for the entire deployment. Therefore, the lowest one-minute pressure will only be reported when the last hourly pressure is less than 1009 hPa. This value may be adjusted downward for buoys deployed in the mid- or high-latitudes.

These measurements will be placed in Section 5, which is the national section of the code that begins with "555". This would have minimal, if any, potential impact on existing software decoders.

Additional Groups:

The following groups will be added to Section 5 of C-MAN and U.S. fixed buoy (i.e. FM-13) reports:

5p_lp_lp_lp_l	p_lp_lp_lp_l is the lowest pressure during the previous hour, in tenths of hPa. This group shall only be reported when the pressure is less than 1009 hPa. Otherwise, the group will be missing. When pressure exceeds 1000 hPa, the leading "1" will be dropped. For example, 1004.2 hPa will be coded as 50042.
7hhmm	hhmm is the hour and minute (UTC) of the lowest pressure during the previous hour
8ddff or 8ddfff	dd is true direction, in tens of degrees, from which the highest peak one minute wind during the previous hour was blowing. For fixed buoys, ff is the associated speed, in units indicated by i_w. For C-MAN reports, fff is the associated speed in knots.
9hhmm	hhmm is the hour and minute (UTC) of the highest peak one-minute wind during the previous hour

Existing national practices code groups:

For reference purposes, the following groups are currently being reported (when data are available) within Section 5 of C-MAN and U.S. fixed buoy reports:

11f₁₀f₁₀f₁₀	f₁₀f₁₀f₁₀ is the 10-meter extrapolated wind speed, in units indicated by i_w
22f₂₀f₂₀f₂₀	f₂₀f₂₀f_{20 is the 20-meter extrapolated wind speed, in units indicated by i_w}
3GGgg	Time of observation (in hours and minutes UTC) of peak 5-second wind during the previous hour
4ddf_mf_m or 4ddf_mf_mf_m	dd is true direction, in tens of degrees, from which peak 5-second wind is blowing; if report is from a fixed buoy, f_mf_m is peak 5-second wind speed during the previous hour, in units indicated by i_w. If report is from a C-MAN, f_mf_mf_m is peak 5-second wind speed during the previous hour, in units indicated by i_w.
6GGgg	End time (in hours and minutes UTC) of the most recent 10-minute average continuous wind measurement.
d₁d₁d₁f₁f₁f₁ d₂d₂d₂f₂f₂f₂ ..... ..... d₆d₆d₆f₆f₆f₆	Direction in whole degrees and speed of the continuous wind data, taken 10 minutes apart, starting during the preceding observation hour. If i_w indicates knots, speeds here are in knots. If i_w indicates meters per second, speeds here are tenths of meters per second.
TIDEH_tH_tH_tH_t	H_tH_tH_tH_t is the 6-minute average water level, above/at/below Mean Lower Low Water (MLLW), ending at the top of the hour, in hundredths of feet. If water level is at or above MLLW, 1000 is added to the water level (in hundredths of feet) for encoding; i.e. an H_tH_tH_tH_t of 1132 means the water level is 1.32 feet above MLLW. Water level at MLLW would be encoded as 1000. If water level is less than MLLW, the height (in hundredths of feet) is subtracted from 1000 prior to encoding. i.e. H_tH_tH_tH_t of 0832 is 1.68 feet below MLLW (1000 - 0168 = 0832).

U.S. Dept. of Commerce
National Oceanic and Atmospheric Administration
National Weather Service
National Data Buoy Center
1007 Balch Blvd.
Stennis Space Center, MS 39529
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Page last modified: June 21, 2005

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