November 13, 2015 Local minimum temperature study

The offshore wind pattern of the past few days has spread very dry air over SoCal
and has resulted in a very wide range of minimum temperatures in and around the 
San Fernando and Conejo valleys and the Santa Monica Mountains.  Santa Ana winds 
blew all night long in many locales and resulted in mild minimums, while some 
wind-protected frost pockets were calm with frigid lows.

Here are low temps for Thu and Fri morning, November 12 and 13, 2015, at selected
stations in the San Fernando Valley, primarily the western SFV.  Included are the
familiar NWS stations and some private/home Weather Underground (WU) and MADIS
stations which I consider trustworthy (at least on minimum temps!).

low temps, flatlands SFV

Thu Fri
40  48  Woodland Hills/Pierce College
36  42  western Woodland Hills WU (Woodlake and Victory)
39  58  West Hills WU (Roscoe and Woodlake)
39  44  Winnetka CW7387 (Sherman Way and Winnetka)
50  67  Chatsworth DW0345 (Plummer and De Soto)
58  65  CSU Northridge
45  49  Van Nuys AP
42  43  Van Nuys WU (Kester and Vanowen)
40  45  Burbank AP
42  44  Studio City DW6087 (Ventura and Colfax)
42  44  Encino WU (Ventura and Hayvenhurst)


low temps, hilltop stations, Santa Monica Mountains and vicinity of SFV

Thu Fri
56  63  Cheeseboro RAWS, north of Agoura, elev. 1707'
55  62  Topanga RAWS, south of Woodland Hills, elev. 1600'
55  63  Calabasas Park Belmonte WU, elev. 1438'
57  64  Malibu Hills RAWS, elev. 1575'
55  62  Porter Ranch above Northridge DW4339, elev. 1634'



low temps, valley bottoms and frost pockets, Agoura/WLV/T.O. area and Santa Monica Mountains

Thu Fri
53  66  Thousand Oaks VCAPCD (Moorpark and Avenida de las Flores, T.O. High School)
36  41  Westlake Village/Reid EW4921 (Hillcrest and Westlake)
32  39  Old Agoura WU
31  36  Agoura/Lost Hills WU
35  43  Bell Canyon WU
27  32  Lobo Canyon WU (south of WLV)
25  30  Paramount Ranch WU (south of Agoura, near Cornell and Mulholland)
30  msg Topanga DW5544
28  32  Malibu Canyon RAWS
59  67  Simi Valley VCAPCD



The low temperature differences between the area hilltops and the coldest frost pockets
 on Thu and Fri are about as large as you'll see for this region.  On Thursday, the
 coldest stations in the western San Fernando valley had mid-upper 30s, while the
 hilltops were in the mid 50s.  At the same time, the outlying frost pockets were
 in the mid 20s to low 30s.  The coldest stations are those in the well-protected
 low spots around Agoura.  The Paramount Ranch station (which had 25F on Thu) is
 located a little bit north of and slightly higher than Paramount Ranch.  The ACTUAL
 ranch may be even a little colder than this station, as it is closer to the valley
 bottom along the stream.


On Thursday night and Friday morning the wind blew without interruption through
 Chatsworth, Simi Valley, and Thousand Oaks.  Minimums were 66F to 67F at the stations
 for these places.  At the Agoura-area frost pockets, protected from the wind, lows were
 30 to 37 degrees colder!  Paramount Ranch dropped to 30F this morning, 33 degrees colder
 than the nearby hilltop stations and 37 degrees colder than Chatsworth and 36 degrees
 colder than Thousand Oaks, both of which are similar in elevation.  Malibu Canyon and
 Lobo Canyon were almost as cold on Friday morning, with 32F.


The NWS often mentions Ojai as its favorite cold spot in Ventura County.  The town
 usually has light winds during Santa Ana wind events, so the nights here are cold
 compared to the breezy areas.  The NWS Ojai station is very close to the stream
 through the valley, and is an impressive frost pocket station. It dropped to 29F
 on Thursday, but that was still warmer than some of the Agoura-area stations.  The
 other stations in the Ojai valley run several degrees warmer than the Ojai NWS station.


low temps, Ojai area
Thu Fri
29  34  Ojai NWS --- East Ojai WU elev. 773'
35  40  Ojai VCAPCD elev. 774' -- Ojai Ave WU
35  40  Ojai South Carillo Rd WU, elev. 758'
44  50  Ojai Fairview Road WU, elev. 1056'

And, the point here, is that all of these valleys have isolated frost pockets and
"cold spots" with impressively low minimums when the wind stops on clear and dry
nights.  The actual location of the weather station with regard to terrain and ground 
cover is a huge factor when it comes to how cold (or not cold) your favorite town is!