Wednesday, July 19, 2017

Moderate To Heavy Storms Across Parts of Metro

Moderate to heavy thunderstorms moved across portions of the metro area during the past two hours or so. View from campus shows the situation  at about 3:00 pm MST above and below at about 3:30 pm.

ALERT rainfall for past three hours, ending at 4:40, pm is shown below - rainfall occurred over most of metro area, except for  the east and south sides. There were three amounts over an inch (plus Atmo which had 1.35" and gusts to 45 mph) and a site with over two inches in the Catalinas. We had 0.34" here with gusts of about 30 to 40 mph. Nice storm and I sat out on porch and enjoyed the cool air and moderate rain.

Mike L asked in his discussion about impacts of upper-tropospheric cyclone/inverted troughs such as the one near El Paso around 1:00 pm today (as per water vapor image above). That's a tough question. When such systems move westward across northern Mexico large MCSs often occur - these can trigger GoM surges if conditions are dry across southern Arizona or cause increased low-level moisture advection into the state, along with increased storm activity.

However, the current IT is blocked by the intensifying 250 mb anticyclone over Sonora and is heading toward the Four Corners. It appears that the dry air ahead of the circulation will basically shift north-northwestward, impacting mostly New Mexico and northeastern Arizona. As this happens it appears that upper difluence may weaken - compared to today - and perhaps even become confluent flow. 

My basic feel is that storms may be more isolated tomorrow, BUT that question will have to await the rest of today's weather and the morning observations.

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