Climate developments in November 2006
Enhanced convection occurred during November, mainly west of the Date Line, from the north of New Caledonia north east to Western Kiribati, including Vanuatu, the southeast of the Solomon Islands, and Tuvalu, although not as strong as in October. Some of the convection over the Solomon Islands and Vanuatu was associated with the passage of tropical cyclone "Yani", the second tropical cyclone this season. The South Pacifi c Convergence Zone (SPCZ) was north of its normal location, with some enhancement west of the Date Line. Convection in the Southwest Pacifi c was quite suppressed in the east between the Northern Cook Islands and Pitcairn Island.
Rainfall was above average (at least 125% of normal) in a few areas in northern parts of New Caledonia and the Austral Islands. Rainfall was 50% or less of normal in parts of Fiji, Northern and central French Polynesia, and less than 25% of normal in the Kermadec Islands, and areas of the Queensland coast of Australia.
Mean air temperatures were 0.5°C or more above average in parts of New Caledonia, Fiji, and 0.5°C or more below average in parts of Southern French Polynesia.
Tropical Southwest Pacific mean sea-level pressures were above average over the northern half of Australia and to the northeast of New Zealand to the region south of the Southern Cook Islands. Pressures tended to be below average in equatorial areas east of the Date Line.
Equatorial surface westerlies occurred in about 35% of observations at Tarawa, about 10% less than in October.
| Country | Location | Rainfall (mm) | % of average | Comments |
|---|---|---|---|---|
| Australia | Townsville | <1 | 1 | Extremely low |
| Kermedec Is | Raoul | 3 | 3 | 2nd lowest on record |
| French Polynesia | Tahiti – Faaa | 37 | 29 | Well below normal |
Soil moisture in November 2006
Estimates of soil moisture shown in the map are based on monthly rainfall for one station in each country. Currently there are not many sites in the water balance model. It is planned to include more stations in the future.
The information displayed is based on a simple water balance technique to determine soil moisture levels. Addition of moisture to available water already in the soil comes from rainfall with losses via evapotranspiration. Monthly rainfall and evapotranspiration are used to determine the soil moisture level and its changes.
Please note that these soil moisture calculations are made at the end of the month. For practical purposes, generalisations were made about the available water capacity of the soils at each site.
At the end of November 2006, Apia soils were at field capacity (full) while Nadi, Nukualofa, and Rarotonga soils were at a dry soil moisture level. Hanan soil moisture levels were moderate.
El Niño/Southern Oscillation (ENSO)
The tropical Pacific Ocean and atmosphere have developed into a clear El Niño state. Sea surface temperature anomalies have steadied in the eastern Equatorial Pacific and continued to rise slightly near the Date Line, while the near-normal anomalies in the Western Pacifi c display the typical "horse shoe" pattern, associated with an El Niño in the subtropics. The NINO3 anomaly steadied around +1.3°C in December, with NINO4 rising slightly to +1.4°C (up from 1.1°C in October). The respective 3-month means are +1.3°C and 1.2°C.
Zonal wind anomalies weakened during November from maximum positive values in October, and are near normal for the time of year.
Continued sub-surface warming along the Equatorial thermocline occurred during November with an extensive area of +4°C isotherm at 100-150m from the Date Line eastwards. The latest 5-day average showed a strong thermocline depression in the central Pacifi c associated with a +6°C temperature anomaly at 100-150m depth near 120°W.
The Southern Oscillation Index (SOI) weakened during November to average at -0.3 with a 3-month mean at -0.9. OLR and tropical rainfall anomalies also refl ect an El Niño like pattern, but with the east-west dipole associated with ENSO events still displaced to the west. An area of enhanced convection is mostly between Papua-New Guinea and the Date Line, with a corresponding suppressed convection area over Indonesia.
OLR anomalies associated with Madden-Julian Oscillation (MJO) developed in early-mid September over the eastern Indian Ocean. The MJO is active but weak, and is expected to propagate into the Western Pacifi c in the fi rst two weeks of December 2006.
Most models show an El Niño state through to the end of February, consistent with last month’s predictions. Seven out of the eleven models predict an easing to neutral during the southern hemispheric autumn 2007: the remaining four model predictions retain El Niño conditions into autumn.
The US International Research Institute (IRI) give an 90% chance of maintaining El Niño conditions "through the next several running 3-month periods" (into early 2007), with a less than 10% chance of becoming neutral during that time. National Center for Environmental Predictions (NCEP) predict continuation of El Niño conditions into early 2007.