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  Extratropical Highlights

  Table of Indices  (Table 3)

  Global Surface Temperature  E1

  Temperature Anomalies (Land Only)  E2

  Global Precipitation  E3

  Regional Precip Estimates (a)  E4

  Regional Precip Estimates (b)  E5

  U.S. Precipitation  E6

  Northern Hemisphere

  Southern Hemisphere


  Appendix 2: Additional Figures

Extratropical Highlights


Forecast Forum

1. Northern Hemisphere

The 500-hPa circulation during November featured above-average heights across the central North Pacific, much of Canada, and Scandinavia, and below average heights over the Gulf of Alaska and the eastern North Atlantic (Fig. E9). Regional aspects of the circulation included a nearly complete disappearance of the mean Hudson Bay trough, and a very strong flow of mild, marine air into central and northern Europe.

The main temperature signals during November included above average temperatures across Canada, the north-central United States, and Europe, and below average temperatures in central Russia (Fig. E1). The main precipitation signals during the month included above-average totals in northern Europe and eastern China, and below-average totals across the United States and eastern Canada (Fig. E3).


a. North Pacific/ North America

The 500-hPa circulation during November featured negative height anomalies in the Gulf of Alaska and western Canada, and positive height anomalies across eastern North America (Fig. E9). This anomaly pattern reflected a deep trough over the Gulf of Alaska, a much weaker than average ridge over western North America, and nearly a complete disappearance of the mean Hudson Bay trough (Fig. E9). This overall pattern was associated with an anomalously zonal flow across continent, which contributed to above average surface temperatures across Canada and the north-central U.S. (Fig. E1).  The largest temperature departures were observed Canada, where values exceeded +5C and were in the upper 90th percentile of occurrences. Much of North America also recorded below average precipitation during November, with the most significant deficits occurring in the East in response to a reduced strength of the Hudson Bay trough (Fig. E3).


b. Europe

The 500-ha circulation during November featured an anomalous trough-ridge couplet over the eastern North Atlantic and Scandinavia (Fig. E9). This pattern allowed for an extensive flow of marine air into the continent, which resulted in above average temperatures throughout Europe, Scandinavia, and western Russia (Fig. E1). The largest departures (+3 to 4C) were observed in northern Europe and western Russia, with much of Europe recording values in the upper 90th percentile of occurrences. The strong onshore flow and associated increase in storminess also contributed to above average precipitation in northern Europe, with totals in Great Britain exceeding the 90th percentile of occurrences (Fig. E3).



  2. Southern Hemisphere


The 500-hPa circulation during November featured above average heights over the central South Pacific and in the areas south of Australia and South Africa, and below average heights near New Zealand, over southern South America, and across the central South Atlantic (Fig. E15). The main temperature anomalies during November reflected warmer than average conditions in central South America and southeastern Australia, and cooler than average conditions in southern South America (Fig. E1). The main precipitation signals during the month reflected above average totals in southeastern South America and portions of southeastern Australia, and a continuation of below average totals in northeastern Australia (Fig. E3).


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Page Last Modified: December 2009
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