Climate developments in November 2009
Enhanced convection along a partially southwest displaced South Pacific Convergence Zone (SPCZ) were seen near northern Vanuatu, northern Queensland, and the eastern edge of Papua New Guinea during November. Most of the region reported well below normal rainfall during the month. Suppressed convection existed in the central portion of the southwest Pacific, particularly around Fiji, southern Vanuatu and New Caledonia. The regional circulation in November was characterised by more frequent low pressure to the southeast of the Society Islands and higher than normal pressure to the northwest of New Zealand and over Australia. This pattern resulted in more frequent easterly and southeasterly anomalies across the much of southwest Pacific, and southerly flow entering the region from the east of New Zealand. Easterly anomalies were particularly evident across Fiji, Vanuatu, and New Caledonia.
Very high rainfall was recorded at only a few stations in the region this past month. In Western Kiribati, 244mm (185% of normal) of rain fell during November, and this is the sixth month in a row with considerable rainfall at that location. Positive rainfall anomalies in Western Kiribati are still more pronounced than in central and eastern parts of Kiribati. In Tonga, 222mm (155% of normal) rainfall was recorded at Lupepau’u, and in the Society Islands rainfall was well above normal at Tahiti (253mm, 196% of normal) and Bora Bora (246mm, 135% of normal). In addition, Funafuti (Tuvalu) received, 418mm of rainfall (176% of normal), which was the highest total reported for the region this past month.
Outgoing Long-wave Radiation (OLR) anomalies, in Wm2 are represented by hatched areas. High radiation levels (yellow) are typically associated with clearer skies and lower rainfall, while cloudy conditions lower the OLR (blue) and typically result in higher rainfall. The November 2009 position of the South Pacific Convergence Zone (SPCZ) southwest of normal near the Solomon Islands, but was incoherent west of Fiji. The average SPCZ position is identified by the dashed green line, which is based on mean January rainfall for the South Pacific. Mean sea level (MSL) pressure anomalies (in hPa) are shown as solid and dashed black lines.
