So, after barely running the irrigation since November, yesterday it seemed time to put some of that expensive municipal water on the groves. No rain was in the forecast, a once promising trough of low pressure for 14 February having changed trajectory and expected to go east of us. Drying winds and continued warmth were in the forecast, after a week of temperatures in the 70s and even over 80. Yes, clearly time to irrigate...
Today it is raining. The temperature has not broken above 47 since about 8:00 this morning. Up to a half inch is expected.
Sometimes the forecasters just get it wrong. Not very often, actually. And a forecast for no rain followed immediately by a day of rain is really rare here.
To their credit, the forecasters keep up links to several forecasts--and the accompanying discussions, where they indicate the models they are using and any doubts--in addition to the current one. And not until about 5:00 this morning was there even any mention of a slight chance of rain. Even at 5:00, the rain chance for the day was given as 30%. It started raining around 7:00, and a forecast issued about the time it started to rain actually downgraded the chance from 60% to 50%. Oops!
By 8:55 a.m. the discussion noted:
NWS DOPPLER RADAR SHOWS NUMEROUS SHOWERS OVER THE CWA [forecast areas] THIS MORNING
WITH SNOW SHOWERS REPORTED IN THE MOUNTAINS...EXTENDING TO SOME
AREAS OF THE INLAND EMPIRE DUE TO LOW WET BULB TEMPERATURES.
DARKENING IN THE WATER VAPOR IMAGERY INDICATES A VIGOROUS SHORT-WAVE
TROUGH DROPPING S THROUGH CA THIS MORNING...
EXPECT VIGOROUS SHORT-WAVE TROUGH WILL DRAW COLD UPPER LOW TO THE
SW...OVER SOCAL BY LATE TODAY. THIS WILL KEEP UNSTABLE CONDITIONS
AND CLOUDS OVER MOST AREAS WEST OF THE MOUNTAINS...
(No, I have idea what "low wet bulb temperatures" are, but I like the way it sounds.)_
Forecasting is an inexact science. And so is knowing when to irrigate. No doubt, had I not turned on the irrigation, it would not have rained.
Labels: weather