Monday, September 8, 2014

Phoenix Gets a Pounding

Someone was going to get a beating from the ongoing monsoon surge and right now it is Phoenix.  Observations from the Phoenix International Airport (KPHX) show that 3.09" of rain has fallen since midnight.

Source: NWS
The NWS has issued flash flood warnings for much of the area.
Source: NWS
The 1200 UTC (0600 MDT) analysis below shows the mix of airstreams feeding the storm system, known as a mesoscale convective system, this morning.  Potentially contributing to this event are moisture sources associated with Tropical Cyclone Norbert, a Gulf of California surge, and even the Gulf of Mexico, although the juiciest air appears to be originating from the Pacific and the Gulf of California.

The potential for thunderstorms that could be locally heavy exists across much of Utah today through tomorrow.  Keep an eye to the sky.  NWS forecasts at


  1. I am accustomed to seeing the term "monsoon" used to define a season of winds rather than a specific wind event. The season often is paired with its own reversal later in the year. Thus, in India the monsoon comes from the West in the Spring and the East in the Fall (or vice-versa -- I can't remember which and don't need to look it up).

    In this thread, the term appears to be used reference to an isolated single event or system which is actually drawing in winds from both West and East and which is not necessarily expected to have a reversed counter-part come October or so.

    I'm a mountaineer, not a meteorologist. Can you expound a bit on the terminology?


    1. Tommy:

      You are correct. The word "monsoon" has traditionally been used to describe seasonal wind reversals. Complicating matters is that there is a lot of temporal and spatial variability in in the monsoon from year to year and even within individual monsoon seasons. In North America, the reversal from westerly to easterly flow is most pronounced and persistent over Mexico, but the northern extend of this shift fluctuates.

      Monsoon influences, however, extend beyond the region that is directly influences by this seasonal wind transition. For example, monsoon moisture can be drawn northward into the western U.S. and sometimes as far north as Canada. I typically use the term "monsoon surge" to describe such weather events. The terms monsoon surge and monsoon break are also used to describe periods of enhanced and suppressed precipitation within the monsoon region.


  2. Thank you very much!

    Are all of your classes taught with such straight forward clarity?

    Tommy T.