Here is the latest weather and El Nino update from our good friends over at Tahoeloco.com July 30, 2009 We’ve seen some big changes in the Tahoe Basin’s weather over the past couple of days, and more are coming into the weekend. Out are the above-average temperatures, low humidity and dry days. In are normal temps (and trending downward), high humidity and thunderstorms. The high pressure ridge that dominated the west for more than a week has degraded just enough to allow an increasing influence from a low-pressure system hanging out over the Pacific. That’s bringing cooler air aloft and creating ideal conditions for thunderstorms. The moisture content in the air right now is about 130 percent to 140 percent of normal. So look for more t-storms to develop today along the Sierra crest and then moving eastward from there. Most of the activity that does develop will bring only rain, but a few isolated hail storms are also possible. As the weekend unfolds, temperatures will be a little bit cooler and the thunderstorms should be less active and not as intense. Look for highs today in the low to mid 80s around the lake, and the low 70s at the higher elevations. Those highs should drop five to ten degrees by Sunday. El Nino Update ocean tempsFor the second week in a row, Sea Surface Temperatures were .9 degrees Celsius above average in the week ending July 27. That means the trend toward warmer ocean temperatures continues and will soon lead to the first three-month period (May, June, July) in which the Oceanic Nino Index is at least a positive .5, which would be the first step toward an official declaration of an El Nino condition later this year. The index, which measures the temperature change from normal in either direction, must be at least a positive .5 for five consecutive, overlapping three-month periods before an El Nino can be declared, so we still have a ways to go. But all signs are pointing to at least a moderate El Nino for the winter of 2009-10, which typically means a wetter, snowier winter for Tahoe. Thanks for the updates guys!