Saturday, June 18, 2011

Precipitable Water (PW) Over Eastern Pacific and Southwest

Over Tucson PW has increased during the past 5 days, as per GPS time-series above (with RAOB PW points plotted for comparison) from ESRL webpage (link is Current PW is around 15 mm, up from values 5 days ago of around 4 mm. The increase has occurred with southwesterly flow from off the eastern Pacific, and was most pronounced yesterday (Friday, June 17th). The higher dewpoints and RH are easing the severity of the extreme wildfire conditions, but only slightly given the strong and gusty winds that are continuing. Note that, as expected, for hot and dry conditions the RAOB values of PW are usually lower than the GPS observations, sometimes by as much as 40% or so. We'll be struggling with the RRS sounding problems from now through at least October, as we try to infer what the real atmospheric Convective Available Potential Energy (CAPE) values are day-to-day.

The CIMSS blended PW product for the eastern Pacific (above) at 1445 UTC this morning indicates that values of around 30 mm have crept considerably north of 20 N on both sides of Baja, with values of around 30 mm currently reaching nearly to the north end of the Gulf of California (GoC), and amounts of 40 to 50 mm are present over the lower GoC.The extensive mT air mass, with highest values of PW, remains mostly south of Cabo Corrientes. Convective clouds have been present along the Arizona/Mexico bordelands the last several afternoons and are present this morning (see the visible satellite image below). However, deep convection and thunderstorms have remained far to the south and southeast of southern Arizona.

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