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

  Stratosphere

  Appendix 2: Additional Figures

Extratropical Highlights

SEPTEMBER 2009

1. Northern Hemisphere

The 500-hPa height field during September 2009 featured above-average heights over Canada , the eastern North Atlantic , and northern Europe , and below-average heights over the Gulf of Alaska , Greenland , and portions of northern Africa and the Middle East (Fig. E9). The main temperature signals included well above average temperatures across Canada , the northwestern United States , Europe , western Russia , and China (Fig. E1). The main precipitation signals included above-average totals across the southeastern quadrant of the U.S. and portions of southern Europe , and below-average totals across eastern Canada , central China , and portions of both Europe and western Russia (Fig. E3).

a. North Pacific/ North America

The s500-hPa circulation during September featured a deep trough over the Gulf of Alaska , a broad trough over the eastern U.S. , and a strong ridge over central Canada (Fig. E9). The mean ridge was associated with well above average temperatures across western and central Canada , with many areas recording values in the upper 90^th percentile of occurrences (Fig. E1). It was also associated with below average precipitation across eastern Canada and the northeastern tier of the United States , with totals in many regions falling below the 10^th percentile of occurrences (Fig. E3). In contrast, a broad trough over the eastern U.S. contributed to increased storminess and above average precipitation across the southeastern quadrant of the country.

c. Eurasia

The 500-hPa circulation during September featured a split-flow pattern over the eastern North Atlantic , in association with positive height anomalies across northern Europe and a broad trough across southern Europe (Fig. E9). This pattern was associated with warmer and drier than average conditions across much of Europe and western Russia , and with large areas of above average precipitation across the Mediterranean Sea , and portions of southern Europe .

In Asia , the strength of the mean upper-level ridge was below average west of the Tibetan Plateau and above average across China (Fig. T22). This pattern contributed to warmer and drier than average conditions in large arts of China . Much of southern China recorded temperature departures in the upper 90^th percentile of occurrences, while rainfall totals across central China were generally in the lowest 30^th percentile of occurrences.

  2. Southern Hemisphere

The 200-hPa circulation during September reflected anticyclonic streamfunction anomalies over northern Australia and cyclonic streamfunction anomalies across the central and eastern subtropical Pacific (Fig. T22). At 500-hPa, the circulation reflected an anomalous zonal wave-3 pattern, with above average heights over the central portions of the three ocean basins, and below average heights pole-ward of Australia and South Africa and over the high latitudes of the eastern South Pacific (Fig. E9).

The main temperature anomalies during September reflected cooler (Fig. E1) and wetter than average conditions over central South America and southwestern Australia , and drier than average conditions in eastern South Africa and eastern Australia (Fig. E3).