Marked pressure drop then rise, 09/11/08. What's the cause?

Mothman

I've crossed referenced this with Annamoe and it was the same there.
My VP/Weatherlink combo only logs pressure every 15 minutes, but there was interesting event today. 9th Nov 08
Pressure was dropping today.
1000mb 11am to 994.3mb at 5pm
Then
17.15 993.8
17.30 991.6
17.45 993.3
18.00 994.2

and now at 23.30 its 997.2

A marked fall from 17.15 to 17.30 and then a marked rise for 17.45.

Would others check their own data, and see if something similar happened and if you log more frequently than every 15 minutes, how did it pan out.

Finally what caused this? Really nothing else of note occurred. No rain, no incresed wind. Wind did back 60 deg for the 15 minute period.

Weather BOFH

Noticed the same thing here, graph attached for the time in question, data logged every minute.

If you look at the pressure animation on xcweather.co.uk you can see the 992 mb line move down south and then back north.

Snowbie

Good spot MM, the pressure drops and rise where from troughs crossing the country. But here in the east mositure was not evident as for the west for the most part but the atmosphere still had the affect on the barometer as trough advancing, passage and wake. Temp dropped also to indicate precip being present.

Notice on my graph the change in bar, temp, wind strength,and rainfall.:)

This data below from the NB text on the graph.
1700 992.9mb
1721 991.9mb
1730 991.5mb
1745 992.5mb
1754 993.0mb

This occured as the trough approached and moved through. In fact several troughd moved over the area today.




Logfile for hour 1700-1800 showing the Time and Bar columns

...............TIME..................BAR
9 11 2008 17 0 06.2 86 04.0 992.9 5 8 235 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 1 06.2 86 04.0 992.9 4 7 245 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 2 06.2 86 04.0 992.8 4 11 223 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 3 06.2 86 04.0 992.7 4 10 237 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 4 06.2 86 04.0 992.7 6 10 217 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 5 06.2 86 04.0 992.7 4 6 214 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 6 06.2 86 04.0 992.7 4 6 227 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 7 06.2 86 04.0 992.7 5 10 219 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 8 06.2 86 04.0 992.6 5 9 214 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 9 06.2 85 03.8 992.5 4 12 214 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 10 06.2 85 03.8 992.4 4 6 193 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 11 06.2 85 03.8 992.3 3 6 222 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 12 06.2 85 03.8 992.2 4 5 204 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 13 06.2 85 03.8 992.2 3 6 253 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 14 06.2 85 03.8 992.2 4 5 215 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 15 06.2 85 03.8 992.2 4 10 221 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 16 06.2 85 03.8 992.2 6 10 231 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 17 06.2 85 03.8 992.2 3 8 223 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 18 06.2 85 03.8 992.1 4 8 213 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 19 06.2 85 03.8 992.0 4 9 219 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 20 06.2 85 03.8 992.0 2 3 206 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 21 06.2 85 03.8 991.9 1 3 211 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 22 06.2 85 03.8 991.9 2 8 231 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 23 06.2 85 03.8 991.8 3 4 220 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 24 06.2 85 03.8 991.7 3 6 219 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 25 06.2 85 03.8 991.6 4 5 209 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 26 06.2 85 03.8 991.6 3 5 226 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 27 06.2 84 03.7 991.5 3 5 200 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 28 06.2 84 03.7 991.5 2 9 256 0.0 1.3 15.6 921.4 6.2
9 11 2008 17 29 06.1 84 03.6 991.5 3 8 233 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 30 06.1 84 03.6 991.5 3 5 200 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 31 06.1 84 03.6 991.5 3 6 188 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 32 06.1 84 03.6 991.6 2 6 255 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 33 06.1 84 03.6 991.6 3 5 231 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 34 06.1 84 03.6 991.6 2 3 268 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 35 06.1 84 03.6 991.6 2 3 224 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 36 06.1 84 03.6 991.6 1 3 223 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 37 06.1 84 03.6 991.6 2 3 256 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 38 06.1 84 03.6 991.8 2 6 266 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 39 06.1 84 03.6 991.9 3 6 272 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 40 06.1 84 03.6 992.0 4 6 271 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 41 06.1 84 03.6 992.1 3 5 269 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 42 06.1 84 03.6 992.2 3 9 243 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 43 06.1 85 03.7 992.3 4 6 254 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 44 06.0 85 03.7 992.4 3 7 259 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 45 06.0 85 03.7 992.5 3 7 251 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 46 06.0 85 03.7 992.6 3 5 247 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 47 06.0 85 03.7 992.7 3 6 257 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 48 06.0 85 03.7 992.8 3 7 243 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 49 06.0 85 03.7 992.9 5 10 246 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 50 06.0 85 03.7 992.9 4 6 272 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 51 06.0 85 03.7 992.9 3 6 264 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 52 06.0 85 03.7 992.9 3 3 253 0.0 1.3 15.6 921.4 6.0
9 11 2008 17 53 06.1 85 03.7 992.9 3 10 253 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 54 06.1 85 03.7 993.0 5 8 241 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 55 06.1 85 03.7 993.0 3 4 237 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 56 06.1 85 03.7 993.0 3 4 248 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 57 06.1 85 03.7 993.0 3 9 236 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 58 06.1 85 03.7 993.0 5 8 237 0.0 1.3 15.6 921.4 6.1
9 11 2008 17 59 06.1 85 03.7 993.0 4 6 250 0.0 1.3 15.6 921.4 6.1

Danno

Same here too! http://www.findu.com/cgi-bin/wxpage.cgi?call=DW0427&last=24&units=metric