Climate developments in November 2005
A large and active area of enhanced convection affected much of Southeast Asia, extending to Papua New Guinea and northern Australia. The South Pacific Convergence Zone (SPCZ) extended from Papua New Guinea towards the Austral Islands, including the Solomon Islands, Fiji, Tonga, Niue, and the Southern Cook Islands. The Inter-tropical Convergence Zone (ITCZ) was well north of the equator. A large region of suppressed convection encompassed Western and Eastern Kiribati, extending south to include Tuvalu, Tokelau, and the Northern Cook Islands.
Rainfall was more than 200% of average in parts of Tonga, the Southern Cook Islands, and northern and southern French Polynesia, and at least 125% of average in parts of Fiji. Vatukoula, Fiji, recorded rainfall totalling 119 mm on the 18th, a new record for that site. November rainfall was less than 75% of average in much of Vanuatu and New Caledonia, the Northern Cook Islands, and central French Polynesia.
Rainfall has been above average in five of the past six months in parts of Fiji’s Eastern Division, Tonga, and Papua New Guinea.
Mean air temperatures were about 1.0 °C above average in Western Kiribati, Wallis and Futuna, Samoa, Tonga, and central French Polynesia, and at least 0.5 °C above average in Tuvalu. In contrast, they were about 0.5 °C below average in parts of Vanuatu. Tahiti-Faaa recorded an unusually warm November, with mean temperatures 1.4 °C above average, and a record high November temperature maximum of 33.9 °C.
Tropical Southwest Pacific mean sea-level pressures continued the tendency to be below average east of the Date Line, being 2 hPa below normal over the Southern Cook Islands. They were above average in the Tasman Sea. Equatorial surface easterlies were persistent along the equator, occurring in about 85% of observations at Tarawa.
| Country | Location | Monthly Rainfall (mm) | % of average | Comments |
|---|---|---|---|---|
| Fiji | Vatukoula | 353 | 236 | Record high |
| Tonga | Niuafoo’u | 486 | 213 | Well above average |
| Cook Islands | Rarotonga EWS | 282 | 207 | Well above average |
| French Polynesia | Hiva Hoa, Autona | 149 | 258 | Extremely high |
| French Polynesia | Gambier, Rikitea | 328 | 231 | Extremely high |
| New Caledonia | Ouloup | 13 | 13 | Well below average |
The tropical Pacific Ocean is in a neutral state (no El Niño or La Niña), but negative sea surface temperature anomalies have strengthened off the South American coast, while those near the Date Line remain positive. The NINO3 SST anomaly was about -0.4°C in November (-0.1°C for September – November), while NINO4 was about +0.4°C (+0.5°C for September – November). The cold subsurface temperature anomaly at about 100 m depth and 140°W has strengthened a little but seems slow moving. The Southern Oscillation Index was weakly negative in November (-0.4), with the 3-month September – November average at +0.3. The equatorial trade winds are near normal in strength. Outgoing longwave radiation (OLR) anomalies indicate some suppression of convection near the Date Line, and enhancement north of Australia, with an enhanced SPCZ in November. The Madden-Julian Oscillation appears to be weak at the moment.
Almost all available models indicate neutral conditions through to winter 2006. Many show a brief period of negative anomalies in NINO3.4, with a recovery by April 2006, and the NSIPP model cools enough to constitute a brief La Niña. The latest US National Center for Environmental Prediction statement calls for neutral conditions, or a weak La Niña, over the next 6-9 months. However, the International Research Institute for Climate and Society summary gives only a about 1% chance of either El Niño or La Niña in the next few months, with neutral conditions "virtually certain" through December.