Mammoth Monsoon Month

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By The Staff

The word monsoon, is derived from an Arabic work for seasonal winds. This year, it brought record August rain to Los Alamos.

On the Arabian peninsula, over India, and in other parts of the world where relatively dry land areas are adjacent to cool oceans, the prevailing winds shift with the seasons.  

Over India, there is a complete reversal, with summertime winds from the southwest and winter winds from the northeast.

Although we do not observe a 180 degree wind shift over New Mexico, we do observe a shift in the winds between the winter (winds from the west and southwest) and summer months (winds from the south).

The prevailing southerly winds during July and August, bring moisture/rains from Mexico, the Gulf of Mexico and the Pacific.

So, the July/August rainy season has taken on the nickname of monsoon.  

The August precipitation total for Los Alamos was 6.01 inches – a whopping 80 percent above the 1971-2000 average of 3.33 inches.  

August was the 10th rainiest August on record; however, we did not come close to the all-time August rainfall record of 11.52 inches, which fell in 1952.

The rainy August almost doubled the January–July precipitation in Los Alamos, with year-to-date totals now being 13.39 inches, just above the 30-year average of 13.22 inches.  

Two thunderstorms produced intense rainfall over Los Alamos County and were accompanied by small stream flooding advisories.

On Aug. 4, 0.78 inches of rain fell at TA-6 within 45 minutes, while 1.30 inches of rain fell at TA-49, also within 45 minutes.

On Aug. 10, 1.03 inches of rain fell in 45 minutes.  The third highest 24 hour TA-6 rainfall total occurred on Aug. 31 when 0.87 inches of rain fell.

On this day, it rained all day – some of the moisture being from the remnants of the eastern Pacific Ocean Tropical Storm Julio.

Rainfall totals across most of Los Alamos County were also above the average August total for the official Los Alamos monitoring location (TA-6 at LANL).

Rainfall totaled 7.81 inches at TA-49 (south boundary of LANL adjacent to Bandelier National Monument), 3.99 inches at TA-53 (Los Alamos Neutron Scattering Center), and 5.33 inches at the North Community volunteer fire station (Arkansas Street).

Precipitation totaled 2.01 inches at TA-54 (just west of White Rock), just below the average August value of 2.17 inches.

High temperatures in Los Alamos and White Rock were normal at 78 degrees and 83 degrees, respectively.  Low temperatures were normal in White Rock at 83 degrees and a degree cooler than average in Los Alamos at 54 degrees.

Winds averaged 6 mph in Los Alamos during August.   

The Climate Prediction Center did well with its August forecast of normal temperatures, but did not predict the well above average August precipitation across New Mexico.  

They are calling for above average temperatures and average precipitation through November.  

Jean Dewart is with WES-Environmental Data and Assessment (EDA), Los Alamos National Laboratory.