Slow start to summer thunderstorm season around Tucson

Prepared at 8:30 am MST 15 July 2007

Yet another day of no storms yesterday in the lower elevations of southeast/south-central AZ. Dry BL air again advected in from the NW, but not as severely as the last couple of days.Quite a slow start to the storm season around here - although Art Douglas has been reporting on the abundant rains to the south along the borderlands.

Misc. points of interest this morning.

Precipitable water and dewpoints are down relative to 24 hours ago.

It's hard to find possible CAPE in the morning sounding, which was about 3 mm on the dry side vs GPS. But there are mid-level buildups and light showers drifting by, so there is a bit of elevated CAPE around.

Winds aloft are very light indicating heavy rain potential, if storms do develop.

Surface pressures have fallen about 3 mb, relative to 24 hours ago over the southern half of state.

The NWS POPs for today are the lowest (10%) of the last several days. However, one of the showers passed over our house between 6 and 7 am MST (I know the timing for certain since it caught me in middle of a morning walk), and actually produced 0.02" of rain in the gauge. Thus, today is the 4th day in July that there's been measurable precip here at the house (grand total to date for July is only 0.26").

The ESE-WNW cloud band that has been south of us the last couple of days is now directly overhead. It appears to be co-located with a weak 300 mb trough/deformation zone. Heavy rains have been associated with this feature to our south yesterday and day before.

The NAM 500 mb analysis at 1200 UTC this morning says that the trough over central TX curls back north over northern MX as a weak inverted trough that extends north into the cloud band mentioned above. I can't see any indication of this feature, but it's again something that the model says is in the great data void to our south. The models do very interesting things with the Texas trough during the coming five days!

Certainly hope that there's some persistence associated with the cloud band and that the heavy storms shift northward with it today.