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Notice: NDBC plans to conduct testing of its DART (tsunameter) network the week of January 12-16, 2009. Click here for details.
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:
5plplplpl |
plplplpl 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 iw. 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 iw |
22f20f20f20 |
f20f20f20 is the 20-meter extrapolated
wind speed, in units indicated by iw |
3GGgg |
Time of observation (in hours and minutes UTC) of peak 5-second wind
during the previous hour |
4ddfmfm or
4ddfmfmfm |
dd is true direction, in tens of degrees, from which peak 5-second
wind is blowing; if report is from a fixed buoy, fmfm is peak
5-second wind speed during the previous hour, in units indicated by iw. If report is
from a C-MAN, fmfmfm is peak 5-second
wind speed during the previous hour, in units indicated by iw. |
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 iw indicates knots,
speeds here are in knots. If iw indicates meters per second, speeds here are tenths of
meters per second. |
TIDEHtHtHtHt |
HtHtHtHt 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 HtHtHtHt 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. HtHtHtHt of 0832 is 1.68 feet below
MLLW (1000 - 0168 = 0832). |
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