“There is no way that we can predict the weather six months ahead, beyond giving the seasonal average.”
~ Stephen Hawking, “Black Holes and Baby Universes”
As we sail into mid-summer, weather is pretty much business as usual. Monday a surge of monsoonal moisture brought cloud cover and a chance of showers to the foothills and much of the southwest. Unfortunately only a few raindrops actually made it to the ground, as we were enveloped in heat and humidity.
Another newsworthy weather condition, but atypical in nature, hit the Midwest: a cold air mass misnamed a “polar vortex” sent temperatures plummeting to those more associated with fall.
Two interesting weather phenomena – the first fairly common during the summer and the second out of the ordinary.
The definition of a monsoon brings to mind images of torrential rains in the sub-tropics. According to the National Weather Service, the term monsoon refers solely to a seasonal wind shift and not to precipitation. Originally used to describe conditions for the Indian subcontinent, monsoonal circulations exist in other regions, namely our own southwest – known as the North American monsoon or Mexican monsoon. The peak period for monsoonal influence in Southern California is from mid July through early September. So we are right on target.
As high pressure builds over Utah, Arizona, Nevada and New Mexico – the four corners – a clockwise air circulation pattern develops. Moisture is drawn north out of the Gulf of Mexico and the Gulf of California into the deserts, mountains and foothills and sometimes lower elevations. Its weather outcome is hard to predict, but the results may range from innocent fluffy white thunderheads to torrential rain, hail and wind with the latter causing loss of life and destruction from flashfloods and rain intensity. Nature gone wild!
Moving east from the potential wild weather out West, we land in the Midwest. Sadly tornados make headline news every year, but another condition caught my eye a few days ago – a polar vortex. An out of the ordinary cold air mass was moving down into the region from the north. A Chicago NWS forecast office, in an online discussion, promoted the event as “a summer version of a polar vortex” (a traditional one hit the city last winter making it the coldest in 30 years.) Whoops! The NWS asked local forecasters to tighten up their use of meteorological terminology.
So, yes there truly are unseasonably cold weather conditions affecting the Midwest, Central Plains and eventually the mid Atlantic states. High temperatures well below 70 and lows into the 40s are possible. A slight ice build up at lake edges is not out of the question either.
No polar vortex action here. The current cold is due to an extreme dip in the jet stream known as a “trough.” This opens the door for a deep upper low out of the Canadian Arctic. Burrr…
Back out West … cooler. Extensive low clouds and fog began to move in Tuesday evening. This onshore flow looks like it will stay in place for several days, covering the coastal areas, extending into valleys and reaching the foothills. Below normal temperatures are expected for most of the region. Patchy drizzle is a definite possibility.
June Gloom has finally arrived. The cooler weather stays for the weekend.
Don’t worry; summer has not left us. Come Tuesday, watch out! A significant warm up is in the forecast. The NWS reports, “Next week very hot. Valley highs expected to top 100 for what could be an extended period.”
Into the pool I go!
Sue Kilpatrick is a
Crescenta Valley resident and
Official Skywarn Spotter for the
National Weather Service. Reach her at firstname.lastname@example.org.