A two day loop of IR satellite imagery, Dynamic Tropopause pressure, and precipitable water shows quite nicely the monsoon surge that brought us showers last night, but also the advection of drier air from the west early this morning.
|Two day loop (1400 UTC 24 Jul – 1400 UTC 26 Jul 2011) of|
dynamic tropopause pressure (shaded), precipitable
water (contours), 925-mb wind, and IR imagery.
Comparing yesterdays 0000 UTC sounding with this mornings 1200 UTC sounding shows substantial moistening of the lower troposphere.
|0000 UTC (purple) and 1200 UTC (red, green) 26 Jul 2011|
soundings from KSLC.
In fact, from 0000–1200 UTC the measured precipitable water increases from 2.31 to 2.75 cm. Although it is unreasonable to expect the 12-h soundings to pick up on the peak after 0000 UTC, the dry bias at 0000 UTC gives a false impression that the PW has increased during this 12-h period, whereas it has actually declined slightly (see GPS meteogram above).
In 2007, Bob Maddox discussed some of the problems with the RRS Sippican Sondes used by the National Weather Service at that time. I don't know if these sondes are still being used, but it certainly appears that problems persist, with significant implications for weather forecasting and long-term climate records.
Some things are a shame, but the decline in the quality of our upper-air observing system is a damn shame.