830 MONTHLY WEATHER REVIEW voo. 97, No. 1 l THE WEATHER AND CIRCULATION QF AUGUST 1 A Manth With Record Warmth in the West
Midtropospheric westerlies in the western portion of the Northern Hemisphere were below normal south of about 45 ’ N. during August. This was accompanied by retrogression of several middle- and low-latitude circulation features during the month, a fairly common development when the westerlies dwindl...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.395.1402 http://docs.lib.noaa.gov/rescue/mwr/097/mwr-097-11-0830.pdf |
| Summary: | Midtropospheric westerlies in the western portion of the Northern Hemisphere were below normal south of about 45 ’ N. during August. This was accompanied by retrogression of several middle- and low-latitude circulation features during the month, a fairly common development when the westerlies dwindle to their low point of the year. July’s east Pacific upper ridge (Andrews, 1969), which has had a long-term history of retrogression, continued its westward motion in August as it moved to the mid-Pacific and phased with a preexisting blocking ridge over northeastern Siberia (fig. 1). The northwesterly flow thus established over a wide latitude band was associated with the southward motion of the Arctic Low north of Alaska and the development of a vigorous Gulf of Alaska trough. Downstream from this trough, amplification spread to the |
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