Western Monsoon Season
So far this summer season the western monsoon has been off to a slow start. The western summer monsoon season is best described as a natural flow of moisture that moves northward from Central America and Mexico into the western states.
In the Desert Southwest and in the Southern and Central Rockies and adjacent plains the majority of the precipitation that falls in the summer comes from the thunderstorm activity associated with this moisture moving up from the south.
The season begins first in the Desert Southwest and far Southern Rockies in June and expands farther to the north into July before peaking in mid August. After some major heat in the Desert Southwest in early to mid June, the monsoonal moisture flow kicked into gear bringing a fair amount of thunderstorm activity to the Desert Southwest.
However, over the past week, the pattern has turned much drier across the far west. The monsoonal moisture flow has been cut off by an active tropical season in the eastern Pacific.
Hurricane Ceclia and a developing tropical cyclone off the southwest coast of Mexico have interrupted the moisture flow. In addition to the tropical activity in the lower latitudes, a stronger and colder than normal storm system moving through the Northern Rockies and the Pacific northwest has sent a drier airmass into the west.
The combination of the tropical activity in the Pacific and a strong storm system in the northwest has interrupted the moisture flow. However, within a week to ten days, the monsoon pattern will get reestablished and the rain chances in the west will increase again.