Noember 2009 Weather Report for Potrerillos Arriba

November marks the winding down of the rainy season, as is clear in the chart below. We had 16.7 inches of rainfall this November, a bit higher than Ricardo Espinosa's 16-year average of 15 inches.

Our average annual rainfall is 175 inches. Our year-to-date rainfall is 163 inches. If December 2009 brings the average December precipitation of 4.6 inches, we'll end the year just 7 inches short of average. This is interesting because in September we had a shortfall of 17 inches, so the extra rain that came early in the year offset the September shortfall. Most of the extra rain came in May - the average that month was 10 inches higher than average. If, then, all other months had been exactly average, the May and September anomalies would give us a year exactly 7 inches short of average.

The National Weather Service Climate Prediction Center/NCEP/NWS issues a monthly El Niño Advisory. The most recent advisory has changed its prediction from one in which "the current El Niño is expected to strengthen and last through the Northern Hemisphere winter 2009-2010" to a more moderate "El Niño is expected to continue and last at least into the Northern Hemisphere spring 2010." Even though the El Niño is no longer expected to strengthen, it is now expected to last into spring. The most recent weekly report continues to predict these conditions.

From our rainfall numbers it would appear that the 2009 El Niño impact on Potrerillos has so far been confined to the month of September. A quick look at the rainfall in Potrerillos during other El Niño years suggests that El Niño droughts tend to last for several months. (Scan the numbers in the highlighted rows and compare them with the average for each month in the "Average" row.)

Other results

The average temperature for November was 70.8 F, exactly the same as it was in October. However, the monthly low of 61.5 F is the coolest low since April, and the monthly high was 93.6, the highest high since March. This is a 32-degree temperature range. Not a big deal for the temperate latitudes, especially in continental interiors, but for us our temperature ranges were less than that, at least in the months of May through October this year.

Average wind speeds (1.7 mph) were about the same as they have been since May. The maximum wind speed was about the same as it has been since April.

The average solar input at 97 watts/cm2, the lowest since February, indicates that we had plenty of cloud cover in November, although we had just about half the rainfall that we had in October, which had a similar cloud cover.

Summary