2003 Monthly Summary

Month

Average Temp.

LAX "Normal"

Avg. High (Max)

Avg. Low (Min)

Total Precip.

LAX "Normal"

Days with at least .1 in. of rain

February

57.0

57.4

62.3 (77)

53.3 (40)

3.52

3.15

6

March

58.6

58.5

68.9 (90)

53.0 (43)

2.47

2.08

2

April

57.6

60.5

66.1 (85)

53.3 (45)

0.53

0.91

1

May

60.1

63.0

63.8 (77)

56.7 (47)

0.77

0.21

2

June

63.7

66.2

65.1 (75)

61.8 (55)

0.02

0.06

0

July

70.2

69.8

75.0 (87)

67.4 (60)

0.02

0.01

0

August

69.6

70.8

74.6 (86)

65.8 (59)

0

0.06

0

September

66.3

69.7

72.3 (86)

64.1 (59)

0

0.22

0

October

65.3

66.4

71.1 (91)

58.0 (53)

0.71

0.43

1

November

57.3

62.2

62.7 (84)

52.7 (37)

0.52

1.22

2

December

54.9

57.6

60.7 (79)

47.4 (36)

1.15

2.21

2

TOTAL

61.7

63.2

67.5 (93)

57.3 (36)

9.77

13.47

16

Highest recorded wind gust: 40.0 mph on March 27

Discussion

With only a few brief exceptions in February and March, 2003 was a remarkably dry year--albeit a bit cooler than average. No month better demonstrated this than the first, which proved to be one of the driest Januaries in Los Angeles history. This was only the fourth January in recorded history in which the Los Angeles Civic Center failed to record any measurable rain. Appropriately enough, the month ended on a record note of a different but related kind: LAX reached the 90-degree mark (91) for the first time ever in January. Indeed, the 93°F temperature we recorded on January 31 in Westchester proved to be the hottest day of the year!

These persistently warm-and-dry conditions came on the heels of an El Nino-influenced, wetter-than-average December 2002. So what happened? Well, those El Nino conditions (i.e., warmer-than-usual sea-surface temperatures in the tropical South Pacific) largely disappeared during January, while another, less understood, fluctuation in ocean temperatures--the Pacific Decadal Oscillation--is presently in its dry weather mode from a Southern California perspective. Thanks to these and who knows how many other random/chaotic and cyclical influences, the Pacific Southwest spent all of January under an amazingly persistent upper-level ridge of high pressure, pushing the usual winter cyclonic storm track well to California's north. This high pressure manifested, in turn, as a cell of surface high pressure whose location migrated back and forth between coastal waters and inland over the Colorado plateau. As a result, Southern California experienced a cyclical pattern back between maritime conditions of on-shore flow (with mild temperatures, high relative humidities, and the typical morning coastal fog and low clouds) and continental "Santa Ana" conditions of off-shore flow (with hotter days and colder nights and low relative humidities). The record-setting final day of the month was one of these Santa Ana days. Even more illustrative was the period between January 15 and January 19, with northerly and easterly winds bringing dry, cloud-free skies, allowing for both cool nights (morning lows in the 40s) and warm afternoons (highs into the 80s). In contrast, the westerly winds of the 20th, 21st, and 22nd, saw a return of Westchester's more typically maritime conditions, with morning clouds and mild temperatures (lows in the 50s, highs in the 60s).