wxgeek's weather-Monsoon Has Officially Begun-Update July 7

Update Thu Jul 7

Yes indeed, the monsoon is in full swing. I saw a 65 deg F dew point at Denver yesterday, which is about the highest you will ever see in CO. 70 deg F dew points in AZ, which are now higher than portions of the midwest and close to Atlanta. I even had a 57 deg F dew point at 9300 ft on Conifer Mtn last evening. The moisture is very welcome relief to the dry winter and spring we have had.

Monsoon pattern will continue for the next several days with the upper level ridge centered near the NM/TX border bringing upper flow across Mexico into AZ and then into CO. Widespread thunderstorms will form once again this afternoon across CO and persists into the evening/nighttime hours. Storms generally form earliest across the mountains and foothills, and persists longer into the night across the Plains. With relatively weak upper level winds, storms are slow movers, generally 5-15 mph, so flash flooding is the main concern this time of year, although large hail is still possible in stronger storms. Afternoon and evening storms likely to persists through the weekend and into early next week. Long range models indicate upper ridge may shift eastward by late next week so we would dry out some.

In general, the remainder of July and August will be influenced by the position of the upper ridge. The flow around the upper ridge dictates where the plume of monsoonal moisture flows. When the upper ridge is centered near NM/TX, this is ideal for moisture to flow into CO. As it moves farther east, we tend to see a drier southwest flow from the Pacific. When the ridge moves farther west, we get warmer but have a drier westerly or northwesterly flow. The upper ridge tends to shift slowly back and forth, so we get a combination of the flows described above. If it stays in one position longer, we get locked into one of the patterns above.

Hopefully everyone now associates this weather with our typical summer weather, at least for July and August, as they are our two generally snow free months during the year.

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The average daily dew point at Tucson has now exceeded 54 deg F for the third consecutive day, which signals the official beginning of the North American Monsoon for 2011. So what does this mean for our weather in Colorado you might ask. We will begin to see additional monsoonal moisture by Tuesday afternoon across most of CO, and the remainder of the week will feature good chances for afternoon and evening thunderstorms. In general, the beginning of the North American Monsoon means we see higher dew points and more clouds in CO. Storms form over higher terrain by late morning to early afternoon, and drift eastward. For our foothills, this commonly means we see initial storms between 11 am and 1 pm, and then a second development later in the afternoon and early evening. In some cases when sub-tropical disturbances move from AZ towards CO, we can see thunderstorms last into the late night hours. In general, July and August are the wettest months in the high mountains and foothills due to the monsoonal moisture.

So I hope everyone has been able to enjoy our nations birthday celebration. The Monsoon also typically helps reduce fire danger with the additional precipitation, at least through August.
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