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October 2009 Weather Report for Potrerillos Arriba
We had 31.2 inches of rainfall in October, higher than Ricardo Espinosa's 16-year average of 28.7 inches. It was a great relief to experience this rainfall after the very dry month we had in September. It did not come close, however, to wiping out the 17.8 inch rainfall deficit experienced in September.
The National Weather Service Climate Prediction Center/NCEP/NWS issues a monthly El Niño Advisory. The most recent advisory states, as it has since earlier this year, that the current "El Niño is expected to strengthen and last through the Northern Hemisphere winter 2009-2010." Their most recent weekly report continues the prediction.
Recent El Niño years are given in the following chart, based on the National Weather Service Climate Prediction Center/NCEP/NWS data.
If we look at the Espinosa data for those years, we see that average annual rainfall during El Niño years is 136 inches, which is 39 inches short of average, and 57 inches short of non-El Niño years. Our year-to-date rainfall this year is 147 inches, which is already higher than the total average rainfall for El Niño years. Nevertheless, that 147 inches is lower than the average year-to-date in October of 154 inches - and this average includes El Niño years. All these data suggest that for our area, the current El Niño episode is not as severe as it has been in years past, but unless November and December bring more rain than usual, we will end the year with a lower than average total.
Other results
The average temperature for October was 70.8 F, the coolest average we've had since February. However, the monthly low of 62.8 F is about the same as for May - September. Monthly high was 88.2, somewhat lower than May's 90.9 but about the same as June - September.
Average wind speeds (1.5 mph) were a bit lower than they have been since May, and the maximum wind speed was the lowest since February.
The average solar input at 98 watts/cm2, the lowest since February, indicates that we had plenty of cloud cover in October, coinciding with the 31 inches of rain for the month.
Summary
The October rainfall of 31.2 inches was slightly above average for the month, and marked a large increase in precipitation since September, but not enough to offset the September deficit. A look at the Espinosa rainfall data for El Niño years in comparison with non-El Niño years shows that we have already had more rain this year than during an average El Niño year, but we are on track to have a lower than average total for the year.