2003年9月 Saint Cloud 天气 Summary

     2003年9月 was an outrageous weather month that defies desciption by the overall statistics. 疯狂的天气包括:

• Days in the first half of the month with highs hotter than mid-July
• Days near the end of the month as cold as the middle of November.
• As many 90-degree highs as frosty mornings
• More than a whole month's rainfall in two days
• 这个月剩下的时间都很干燥, producing lingering problems with low stream flow, 湖的水平, 以及它们对农作物的影响, 树叶, 和草坪.

    Because of the wild variations of extremes in September, the numbers for the month don't really tell the story, 但我们还是把他们赶走吧. 九月份的平均气温是58度.6°F, 1.比正常温度高2°F. 九月份的总降雨量是3.94 inches, more than an inch above normal.

     So, what temperature statistics can document our wild swing from summer weather to early winter? The transition happened on September 19 (见9月每日统计). For the first 18 days of the month, Saint Cloud had an average high temperature of 79.华氏6度，平均最低华氏50度.5°F. This average high temperature was typical of middle August (见8月日平均值). 9月6-8日, Saint Cloud had its first September heat wave (3 consecutive days with a high of at least 90°F) since September 1978. Conversely, during September 19-30, Saint Cloud had an average high of 59.3华氏度，平均最低38度.4°F. These average temperatures were typical of mid-October (见10月日平均值). The weather of the last week (highs in the middle 50's and lows in the upper 20's to lower 30's) are typical of the first week in November (见11月日平均值). There were three days with low temperatures at or below freezing. 第一次霜冻是在9月25日, 只比平时早一天, but surprising considering conditions earlier in the month.

     Were this September's roller-coaster temperatures unusual? It is not that unusual to have a spring or fall month with both 90°F highs and 32°F lows. In recent years, September 1998, May 2000, and May 2002 had both extremes. 然而, it is highly unusual to have so many days of each. The last time that Saint Cloud experienced at least three 90°F highs and three 32°F lows in the same month was September 1976. By the way, that September was even more extreme than this one, with 10 90°F highs and 6 32°F lows.

    Part of the reason for the extremes were the dry conditions which have plagued Minnesota since mid-July. Since dry soil heats up and cools down more easily than wet soil or puddles, the soil conditions helped to allow warm air masses to generate warmer temperatures and cold air masses generate colder temperatures. Of course, the steering wind shift changes. 在这个月的前三分之二, the upper-level winds primarily blew from west to southwest flow, bringing air that had descended the east slopes of the Rockies into the Dakotas and Minnesota. 然而, the same pesky high pressure system that kept cool air flowing for much of the late winter and early spring from last season set up again. 昨天, 阿拉斯加中部的最高温度达到60华氏度, but only made it to the lower 50's in central Minnesota.

    是的, we got above normal rainfall this past month, but the delivery of the rain did not help all of our problems from the late summer dry period. 在这三个人中.9月份的降雨量是94英寸.45 inches fell on September 10-12 as a slow-moving cold front allowed repeated bands of thunderstorms to move over central Minnesota. 有2个.11号一天就下了56英寸的雨. This was the 5th rainfall event of at least an inch during 2003, which has already equalled the annual average (这里的降雨量达到了历史上的1英寸), but this wasn't enough rain to break the daily rainfall record for the 12th (3.35英寸(1980年)，也不等于4英寸.39 inches that Saint Cloud picked up in about 8 hours on September 5-6 of last year. The heavy rainfall helped to ease a serious dry period, as noted by the Minnesota State Climatologist's Report on the dry middle and late summer. 尽管九月中旬下了大雨, Saint Cloud's rainfall since July 15 is still nearly three and a third inches below normal.(参见下面的降水统计). 干燥的条件显示在 国家干旱监测 for September 23 as moderate drought covers the southern three-quarters of the state with severe drought in west central Minnesota. This is also being reflected in low stream and river flow in the area.

     The prospects for warmer weather and more rain are uncertain. With the British Columbia high locked into place, high temperatures will continue to be 10-20 degrees below normal through early next week with a brief break tomorrow. Lows will mostly remain in the 20's and 30's, which is also 10-15 degrees below normal. Beyond that, the high should break down, allowing milder air into Minnesota. Is this a recurring pattern that will shape much of the cold season to come? 我现在还不能说.

    二零零三年九月统计数字