PRESRR

[flyingcheesehead]

Check out the rapid rise in altimeter settings:

KMSN 250653Z 26005KT 9SM CLR M16/M19 A3025 RMK AO2 SLP263 T11611189
KMSN 250553Z 23005KT 8SM CLR M16/M18 A3021 RMK AO2 SLP248 4/015 T11561183 11100 21156 410061156 51034
KMSN 250453Z 00000KT 8SM CLR M15/M18 A3018 RMK AO2 SLP236 T11501178
KMSN 250353Z 26004KT 8SM CLR M14/M17 A3016 RMK AO2 SLP230 T11391172
KMSN 250253Z 27007KT 8SM CLR M13/M17 A3011 RMK AO2 SLP211 T11331167 53044
KMSN 250153Z 29006KT 8SM CLR M12/M16 A3006 RMK AO2 SLP194 T11221161
KMSN 250053Z 28009G18KT 8SM CLR M11/M15 A3002 RMK AO2 SLP181 T11111150
KMSN 242353Z 27008KT 7SM FEW015 M10/M14 A2998 RMK AO2 SNE41 SLP164 4/015 P0000 60000 T11001139 11022 21100 53066
KMSN 242253Z 28010G17KT 4SM -SN FEW020 SCT026 M08/M12 A2991 RMK AO2 PRESRR SLP142 P0000 T10831122
KMSN 242153Z 28009KT 6SM -SN BKN024 M07/M11 A2984 RMK AO2 SNB24 PRESRR SLP116 P0000 T10671106
KMSN 242053Z 28010G20KT 7SM BKN024 M06/M09 A2977 RMK AO2 SNE08 SLP094 P0000 60000 T10561094 53041
KMSN 241953Z 28013G21KT 5SM -SN OVC019 M05/M09 A2972 RMK AO2 SLP075 P0000 T10501089
KMSN 241932Z 30010KT 5SM -SN BKN019 BKN080 M05/M08 A2970 RMK AO2 P0000

What are the criteria for PRESRR? It's only listed twice, but the pressure appears to have maintained the same rate of change in the following hour as well. Also, in a 74nm trip, the altimeter setting went from 2979 down to 2964, and by the time we returned it was 2992. When checking in with a new controller, I was twice off by nearly 200 feet after changing the altimeter setting!

 

[KennyFlys]

From Aviation Weather Services Book - Advisory Circular 00-45F
Page 3-25

3.1.3.13.21 Pressure Rising or Falling Rapidly
[FONT=Arial,Arial][FONT=Arial,Arial]At designated stations, the reported pressure is evaluated to determine if a pressure change is occurring. If the pressure is rising or falling at a rate of at least 0.06 inch per hour and the pressure change totals 0.02 inch or more at the time of the observation, a pressure change remark is reported. When the pressure is rising or falling rapidly at the time of observation, the remark [/FONT][/FONT]PRESRR [FONT=Arial,Arial][FONT=Arial,Arial](pressure rising rapidly) or [/FONT][/FONT]PRESFR [FONT=Arial,Arial][FONT=Arial,Arial](pressure falling rapidly) is included in the remarks. [/FONT][/FONT]

 

[flyingcheesehead]

From Aviation Weather Services Book - Advisory Circular 00-45F
Page 3-25

Right... But there were three hours where the pressure went up by .07 per hour, and only two of them showed PRESRR.

 

[KennyFlys]

Right... But there were three hours where the pressure went up by .07 per hour, and only two of them showed PRESRR.

We normally at the entire hour as the duration of the change. I'm speculating change can take place in a matter of ten minutes preceded by fifty minutes of stable pressure.

I'd think the PRESRR would also be noted on 2353Z report. But, I think if it's comparison of time as described above, it may not show up.

Maybe a quick change then a long period of stability followed by another quick change? It's just a guess on my part.

The other side of it is since they are automated reporting stations, I'd be looking for the fact that it has "Human Augmentation" so the numbers are backed up. If I'm flying into a non-towered field, I'll be looking for the nearest towered field so there's some verification of the numbers observed.

ID ---Time ----Altim---Net Change
KMSN 250653Z A3025 +0.04
KMSN 250553Z A3021 +0.03
KMSN 250453Z A3018 +0.02
KMSN 250353Z A3016 +0.05
KMSN 250253Z A3011 +0.05
KMSN 250153Z A3006 +0.04
KMSN 250053Z A3002 +0.06
KMSN 242353Z A2998 +0.07
KMSN 242253Z A2991 +0.07 PRESRR
KMSN 242153Z A2984 +0.07 PRESRR
KMSN 242053Z A2977 +0.05
KMSN 241953Z A2972 +0.02
KMSN 241932Z A2970