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Thunder Sign-On/Off Procedures


You can avoid transmitting inaccurate ASOS information by following easy sign-on, sign-off procedures. By using the SIGN function from the 1-Minute Screen, a user can sign-on/off ASOS at the Observer (OBS), Air Traffic Controller (ATC), Technician or System Manager password levels.

Depending on the level of augmentation and backup required, the person responsible for providing augmentation and backup (i.e., the observer) may be signed-on ASOS at either the OBS or ATC password levels. When the observer signs on ASOS, he/she assumes responsibility for augmenting for a thunderstorm. This responsibility exists until a thunderstorm sensor is installed or lightning data are provided to ASOS from the lightning detection network. When both the OBS and ATC are not signed-on, ASOS will encode Thunderstorm Information not Available (TSNO) in the remarks section of any METAR/SPECI report. (See Figure 1.) After either the OBS or ATC signs-on ASOS, the TSNO remark is removed. (See Figure 2.)

Figure 1


08:21:09 07/16/96 1221Z SILVER SPRING METRO CENTER 2
SKY = OVC001 VISIBILITY = 10SM TEMP/DEWPT = 24.4 /18.9 C 76 /66 F WIND DIR/SPD = 280/09 PRESENT WX = ALTIMETER = 30.15 REMARKS = RMK AO2 PWINO TSNO METAR KSP1 161159Z AUTO 28005KT 10SM OVC001 24/19 A3014 RMK AO2 SLP336 70001 T02390194 10239 20217 51026 PWINO TSNO $ PRINT REVUE SIGN AUX

Figure 1: ASOS 1-Minute Screen with nobody signed-on ASOS. Until ASOS is equipped with either a thunderstorm detection sensor or provided lightning information from a lightning detection network, TSNO (Thunderstorm Information not Available) will be placed in remarks when both the Observer (OBS) and Air Traffic Controller (ATC) are not signed-on the system.


Figure 2


08:22:29 07/16/96 1222Z SILVER SPRING METRO CENTER 2
SKY = OVC001 VISIBILITY = 10SM TEMP/DEWPT = 24.4 /18.9 C 76 /66 F WIND DIR/SPD = 280/09 PRESENT WX = ALTIMETER = 30.14 REMARKS = RMK AO2 METAR KSP1 161159Z AUTO 28005KT 10SM OVC001 24/19 A3014 RMK AO2 SLP336 70001 T02390194 10239 20217 51026 PWINO TSNO $ PRINT GENOB CMD REVUE TWR SIGN EDIT AUX

Figure 2: After the OBS or ATC signs-on ASOS, the TSNO remark is removed from the REMARKS section. Note that the last transmitted METAR report has TSNO encoded in remarks since both the OBS and ATC were not signed-on at the time the report was generated.


When a shift changes and the new person uses the same OBS/ATC password level and the same ASOS Operator Interface Device (OID), the departing person need not sign off. When the oncoming OBS/ATC signs on ASOS, the system automatically signs off the previous person. (At part-time stations, of course, the OBS/ATC will have to sign-off at the station’s closing time.)

If the person being relieved signs-off ASOS and the oncoming OBS/ATC does not sign-on immediately, ASOS will not have oversight and erroneous information may be transmitted locally and long-line. A break in OBS/ATC oversight will be obvious during a thunderstorm. In this case, ASOS automatically will remove the thunderstorm (TS) from the PRESENT WX field and provide the TSNO remark; the thunderstorm will cease to exist without ASOS providing an ending time. When the oncoming OBS or ATC signs on, and if the thunderstorm has ended by ASOS because the previous OBS/ATC signed off, the oncoming OBS/ATC will have to restart the thunderstorm.

Since this break in ASOS oversight creates a problem in accurately reporting the weather at the station, it is important to avoid these breaks. A station can avoid this problem by having the oncoming OBS/ATC sign on without the departing OBS/ATC signing off. (See Figures 3-5, below). To avoid problems related to sign off/sign on at shift changes, just have the oncoming observer sign on ASOS. This will automatically sign-off the observer being relieved and provide continuous oversight of the ASOS observations.

Rick Parry
ASOS Program Office
(301) 427-2175

Figure 3


08:28:15 07/16/96 1228Z SILVER SPRING METRO CENTER 2
SKY = OVC001 VISIBILITY = 10SM TEMP/DEWPT = 25.0 /18.9 C 77 /66 F WIND DIR/SPD = 290/08 * PRESENT WX = TSRA ALTIMETER = 30.15 REMARKS = RMK AO2 TSB25RAB25 P0000 SPECI KSP1 161227Z 29008KT 10SM TSRA OVC001 25/19 A3015 RMK AO2 TSB25RAB25 P0000 $ PRINT GENOB CMD REVUE TWR SIGN EDIT AUX

Figure 3: The observer augmented for a thunderstorm (TS) and provided backup to the present weather sensor by entering rain (RA) in the PRESENT WX field.


Figure 4


8:32:26 07/16/96 1232Z SILVER SPRING METRO CENTER 2
SKY = OVC001 VISIBILITY = 10SM TEMP/DEWPT = 25.0 /19.4 C 77 /67 F WIND DIR/SPD = 260/06 * PRESENT WX = RA ALTIMETER = 30.15 REMARKS = RMK AO2 TSB25RAB25 P0000 TSNO SPECI KSP1 161227Z 29008KT 10SM TSRA OVC001 25/19 A3015 RMK AO2 TSB25RAB25 P0000 $ SENSORS IN MANUAL MODE: PRESENT WEATHER FREEZING RAIN PRINT REVUE SIGN AUX

Figure 4: After the observer signs-off, the thunderstorm (TS) is automatically removed from the PRESENT WX field, an end time for the thunderstorm is not encoded in the remarks section, and TSNO is provided as a remark.


Figure 5


8:34:33 07/16/96 1234Z SILVER SPRING METRO CENTER 2
SKY = OVC001 VISIBILITY = 10SM TEMP/DEWPT = 25.0 /19.4 C 77 /67 F WIND DIR/SPD = 280/07 * PRESENT WX = RA ALTIMETER = 30.15 REMARKS = RMK AO2 TSB25RAB25 P0000 SPECI KSP1 161227Z 29008KT 10SM TSRA OVC001 25/19 A3015 RMK AO2 TSB25RAB25 P0000 $ SENSORS IN MANUAL MODE: PRESENT WEATHER FREEZING RAIN PRINT GENOB CMD REVUE TWR SIGN EDIT AUX

Figure 5: When the oncoming observer signs-on the system, a thunderstorm is not re-encoded in the PRESENT WX field. If the oncoming observer needs to augment for a thunderstorm, the remarks section will have two begin times encoded without an end time.


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