Aside from the high temperatures however, what became more noticeable throughout southern California in July was dew point and humidity levels equaled those found in tropical zones.
Was July 2006 a result of global climate change -- and perhaps indicative of what is yet to befall Los Angeles in the future? Read long-range weather predictions for California.
There is no clear answer when predicting climate change past an educated guess -- hence the debate surrounding affects of global warming itself. Global weather patterns know no boundaries between southern California, the Rocky Mountain states, and across the Atlantic into Europe and into Asia and cycling back again into the Pacific. While one unusually hot day in one location (or a record breaker) is not as relevant to the whole of a pattern -- sustainable long term trends however are far more telling of climate change, which is why studying and understanding California's record July weather is relevant.
Perhaps southern California's July weather is written off as being a fluke -- just as was the unheard of yet severe thunderstorm and hailstorm outbreak for four days in New Delhi and Mumbai, India, during March 2006 smack in the middle of their dry season. Hail could be a fluke too for Buenos Aires, Argentina, on 26 July 2006 when hailstones the size of plums and grapefruit injured more than one dozen people, knocked out power and windows, and damaged automobiles.
Atmospheric conditions suggest that widespread unusual events are indicative of a larger change in patterns. Southern California was not alone in recording unusual weather patterns during July. Germany's weather statisticians did not wait for the month to close before declaring July 2006 the country's hottest and sunniest on record. The average high was approximately 81 degrees, or 8 degrees higher than historical average.
Paris, France, too logged a record July. The average July temperatures in Paris are 76 and 57 degrees: Not a single day or night were that cool. The average high as of July 29 has been 88 degrees and the overnight low 68 degrees. Twelve days exceeded 90 degrees, the coolest evening was 61 degrees. July 2006 daytime high temperatures in Paris were 6 degrees warmer than the deadly heat wave of 2003.
Feel the Ocean Air
San Diego as of press time --July 29-- has not experienced a temperature reading below 70 degrees for 21 consecutive days and nights and should end up with an average high of 81 and low of 72 degrees for the month. The coolest reading for July 2006 was 68 degrees or five degrees higher than the monthís average low. Dew points jumped to unusually high levels during the second half of the month (into the 60s and low 70s) as the Pacific Ocean warmed into the unusual mid-70s range.
The Los Angeles basin and all points west of the mountains in southern California are a hotbed of microclimates due to topographical and Pacific Ocean influences. One temperature location does not reflect patterns experienced in the San Fernando Valley and Orange County or the Westside of Los Angeles as each region and elevation has its own set of climate rules. Typically the low-lying coastal plain is moderated from extreme heat due to a daily sea breeze, whereas points further away from the coast experience low humidity and warmer afternoons, which easily reflect a 20-degree difference between coast and valley locations.
Sea breezes work when the ocean water temperature is a chilly and murky 60 degrees -- which was not case as July 2006 wore on. The Pacific coastal waters off southern California during July 2006 have warmed into the mid-and-upper 70s from Point Conception south to the Mexican border and out at least 40 miles. On July 29 the water temperature at San Clemente Pier, in Orange County, was 78 degrees -- or the same water temperature at Waimea Bay, Hawaii. The reason was not a result of El Nino or La Nina, but from localized weather patterns begun in early June.
Ships further out to sea off southern California show water temperatures higher now than what is typical for the area in July at 67 degrees approximately 121 nautical miles west of San Diego, and 71 degrees 12 miles southwest of Santa Barbara. These figures are about 10 degrees warmer than historical average and unusually widespread.
Wind Pattern Shifts
The reason for warmer ocean temperatures, and thus warmer and more humid landmass air temperatures in July were a result of two important events.
1.) Prevailing northwesterly ocean surface winds, which generally flow southeast along the coasts of Oregon and California to Point Conception have been weak and even taken on at times a more southerly / southwesterly direction off the coast of central and northern California. Once the winds round Point Conception, they have abated almost entirely.
2.) The high pressure system responsible for the desert southwest's summer monsoon. (Discussed in the next section.)
Ordinarily, the northwesterly winds are responsible for a great deal of upwelling along the California coast. Colder ocean water below the surface is pulled to the coastline on wind-generated surf and works itís way southeast. With this influence abated, as was the case in July, the shallower ocean depths retain solar energy.
Consider that in July 2005 --a typical wind pattern year along the California coast-- the water temperature 121 miles off the coast of San Diego was 57 degrees (10 degrees cooler than in July 2006) and at San Clemente Pier the water was 69 degrees, or 9 degrees cooler than present day. Northern California ocean water in July typically runs in the low to mid-50s, with high 40s not unusual in July, but even those water temperatures are running one to three degrees above average. As of press time however northern California's weather patterns have adjusted back to what would be considered normal for July with fog and clouds along the coast and air temperatures barely reaching 65 degrees in San Francisco midday.
Cause and Effect
The northwesterly wind pattern usually rounds Point Conception and enters the coastal waters of southern California and heads toward the central Baja Peninsula. The wind can sometimes be deflected by the channel islands in which case spins into what is called a Catalina eddy or micro surface low.
As desert heat builds inland in excess of 100 degrees, the Pacific-cooled air (some 30 and 40 degrees cooler) is pulled inland across southern California. With the cooler air in motion, the coastline is kept oftentimes cloudy and the sun is blocked from heating surface water to a great extent. This pattern is most noticeable in May and June, but usually decreases in July as the Pacific warms slightly to varying degrees of between 66 and 71 degrees, and the southwestern monsoon season is in full swing.
In early June 2006 the monsoonal high pressure system in the four-corners region established itself early. Mid-level moisture streamed into Tucson and Phoenix, Arizona, and Las Vegas, Nevada, in the first few days of June and all three cities were slammed with thundershowers, flash flooding, and wind damage. The monsoon season could be said to have arrived one month early, but moisture subsided for the most part until later in the month and new record high temperatures were noted instead of unusually high moisture levels.
The event could have been written off as unusual, however the pattern has been steadfast now for nearly two months.
During June the monsoon system flirted with southern California at the surface, but pushed further west at the mid levels, out and over the Pacific, further disrupting coastal eddy and marine layer influences as the northwesterly flow abated in northern California. Mid and low level wind flows across southern California shifted to an offshore flow, giving the region above normal temperatures -- but average to below average dew points (30s and 40s.) This pattern abated slightly for the first week of July at the surface, but continued at the mid levels as tropical moisture increased into the system from the gulfs of both Mexico and Baja California.
Humidity levels increased in early July, but backed off in the second week. Forecasters continued to predict the four corners high pressure system would move east, returning southern California's pattern to a more typical west-to-southwest flow aloft. During July 2006 however --with the pattern unchanged-- the ocean wind patterns off southern California provided a new twist.
Around 10 July 2006 coastal winds along Baja California started to head offshore --west/northwest-- in response to numerous easterly waves leaving old Mexico.
The four-corners high-pressure system reinforced off shore gradients in Baja and southern California -- keeping cloudless skies with nocturnal offshore winds at the 1,000-2,000 foot level that prevented any marine influence from developing.
Foothill regions in Santa Barbara, Ventura, Los Angeles, Orange, and San Diego counties experienced sundowner winds, which pushed midnight and pre-dawn temperatures above the 90-degree mark on northeasterly winds of 30 miles per hour. Montecito, California, at elevation 1,500 feet recorded five consecutive days and nights in early July with air tempertatures at or above 85 degrees, and yet the recording station is only 2 miles from the cool Pacific Ocean in Santa Barbara county.
In response to cloudless skies and lack of northwesterly surface winds, the Pacific Ocean had the full effect of solar heating from late June through all of July. With an ocean water temperature average having warmed to 75 degrees by mid-July, it was taking very little solar energy to warm the air into the 80s even at the beach. The air mass grew increasingly moist, which held nighttime temperatures above 70 degrees.
On 28 July the air mass in southern California had grown saturated enough that there was little difference between temperatures along the coast and those up against the foothills -- traditionally 20 degrees warmer in July. By late afternoon higher elevations were shrouded in low cloud cover, dew points were in the 60s/70s at a time of day usually with dew points in the 30s.
After sunset, clouds formed everywhere on the 28th and in some cases produced light showers notably in San Diego county's coastal region as temperatures met dew points -- in the 70s.
Given the same conditions under what would be considered 'normal' temperatures --with the ocean at 65 degrees and landmass air temperatures of about the same or cooler-- the interaction of these patterns would have passed unnoticed.
Low clouds and fog creeping inland is a mainstay pattern in southern California, but not with temperatures of 10 degrees above average and dew points in the 70s. Such measurements are indicative of weather patterns in Hawaii.
Outlook for August
Nothing has budged the four-corners high-pressure system since it established itself 2 June 2006 -- just as nothing pushed out high-pressure systems responsible for heat in Germany and France and all of central Europe for about the same period.
As the earth's axis now begins its progression away from summer solstice, all of these patterns will indeed change. Even as of press time, temperatures in Paris, Hamburg and Berlin (Germany,) are all expected to crash within the next week into the 60s for daytime highs finally bringing relief and much needed rainfall.
Once Europe returns to a more average pattern for August, expect a domino affect to work around the northern hemisphere in six to eight weeks.
California's patterns however are more difficult to assess, unlike the northern latitudes, southern California is less dependent upon solar heating during summer months to shift weather systems -- mainly because a central Pacific high blocks frontal systems from reaching as far south as California from late June through early September.
The same four-corners high-pressure system responsible for southern California's phase of hot and humid weather in July is the same pattern responsible for Santa Ana wind events -- extremely dry and windy conditions usually saved for the months of October through March. Temperatures during those events are usually far above average, but they too can bring the coldest nights of the year.
Going into August --now with the Pacific Ocean warmed by as much as is probable-- it is conceivable that little will change in the current pattern until the northern latitudes prepare for the fall equinox. However, if the northwesterlies strengthen along the Oregon/California coast, water temperatures will drop rapidly from upwelling and air temperatures will follow, especially at the coast.
As with all predictions - they are educated guesses based upon numerous historical trends and computer modeling data. The National Weather Service models suggest above average temperatures for southern California through October with little or no measurable rainfall, whereas it predicts below average temperatures for Arizona with more rainfall than average.
Despite predictions of an active Atlantic Ocean hurricane season -so far- it has been a wash. The Pacific ocean hurricane season has been fairly active, but not robust.
Nonetheless, if the coastal waters off southern California and Baja California remain sustainable to tropical storms moving northwest, the threat of a hurricane strike in the region grows during the next eight weeks. In such an event any amount of rainfall in excess of 1 inch would be considered above normal for Los Angeles and San Diego prior to mid-October.
Fast moving hurricanes have hit New England's coast at times when the ocean temperature in the region was 10 degrees cooler than what is presently the case in southern California. The difference is that due to the Gulf Stream off the New Englandís coast, the water temperatures climb dramatically away from the shore, which lend hurricane support all the way up to landfall. The opposite is true in California where water temperatures are lower further out to sea.
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