The Island Climate Update
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Number 64, January 2006 The Island Climate Update December’s climate • The South Pacifi c Convergence Zone (SPCZ) extended from the Solomon Islands towards the Southern Cook Islands; high rainfall in parts of Fiji, northern Tonga, and French Polynesia • Suppressed convection occurred around the Date Line in the central equatorial Southwest Pacifi c; below average Collaborators rainfall in New Caledonia and the Southern Cook Islands • Well above average air temperatures occurred in New Australian Bureau of Meteorology Caledonia, Fiji, and central and southern French Polynesia Meteo France El Niño/Southern Oscillation and seasonal rainfall Fiji Meteorological forecasts Service • The tropical Pacifi c remains in a neutral state with some NOAA National features of a weak La Niña Weather Service • Enhanced convection expected in the Southern Cook NOAA Climate Islands Prediction Centre • Below average rainfall likely in Western and Eastern Kiribati (CPC) International Research Institute for Climate and Society European Centre for Medium Range Weather Forecasts UK Met Offi ce World Meteorological Organization Climate developments in December 2005 large area of suppressed convection affected the central A equatorial Pacifi c extending to parts of the Northern and Southern Cook Islands, and the Society and Tuamotu Islands of French Polynesia. The South Pacifi c Convergence Zone (SPCZ) extended from the Solomon Islands to just north of the Southern Cook Islands, resulting in above average rainfall over parts of Fiji, Tonga, and French Polynesia. The Intertropical Convergence Zone was well north of the equator. Rainfall was less than 50% of normal in the Southern Cook Islands, New Caledonia, Norfolk Island, and southern parts of both Tuvalu and Tonga. Mean air temperatures were about 1.0 °C above average in central and southern French Polynesia, and at least -2 0.5 °C above average in Vanuatu, New Caledonia, Tuvalu, Outgoing Long-wave Radiation (OLR) anomalies, in Wm . The December 2005 position of the SPCZ, as identifi ed from total rainfall, is indicated by and the Southern Cook Islands. Unusually warm December the solid green line. The average position of the SPCZ is identifi ed by the air temperatures were recorded at several sites in parts of dashed green line (blue equals high rainfall and yellow equals low rainfall). New Caledonia, Fiji, and French Polynesia. The December 2005 position of the Intertropical Convergence Zone (ITCZ), as identifi ed from total rainfall, is indicated by the solid blue line. Tropical Southwest Pacifi c mean sea-level pressures Country Location Monthly Max Comments continued the tendency to be below average east of the Date Temp (°C) Line, although this was not as marked as in previous months. They were above average over northern Australia, and across New Caledonia Pouembout 37.1 Equal high New Caledonia toward Fiji. Equatorial surface easterlies Fiji Labasa Airfi eld 32.6 Equal high were persistent along the equator, occurring in about 92% French Polynesia Tahiti – Faa’a 28.1 Record high of observations at Tarawa. French Polynesia Rikitea 25.2 Record high Sea surface temperature anomalies (°C) for December 2005. Mean sea surface temperatures (°C) for December 2005. he tropical Pacifi c Ocean is in a neutral state with near the Date Line and across the Pacifi c. Outgoing longwave Tsome features of a weak La Niña. Negative sea surface radiation (OLR) anomalies indicate suppressed convection temperature anomalies continue to strengthen off the South near the Date Line, but much enhancement north of Australia American coast, while those near the Date Line have eased into Asia. Although the monsoon trough appears to be to near normal. The NINO3 sea surface temperature (SST) becoming organised over north Australia, the Madden-Julian anomaly was about -0.7 °C in December (-0.3°C for October– Oscillation (MJO) continues to be weak. December), while NINO4 was about +0.2°C (+0.4°C for October–December). The cold subsurface temperature Four of the ENSO forecast models show weak La Niña anomaly has surfaced across from the Date Line eastwards, conditions for the January to March period, with all trending and further cool anomalies occurred in the subsurface. back to neutral conditions through April-September 2006. The latest NCEP/CPC statement calls for neutral conditions or a The Southern Oscillation Index (SOI) was near neutral in weak La Niña over the next 6–9 months. The IRICP summary December (-0.1), with the 3-month October–December gives a 10% chance of La Niña in the next few months, average at +0.2. The equatorial trade winds have strengthened with neutral conditions most likely through the summer. The Island Climate Update, No. 64, January 2006 Page 2 Tropical rainfall outlook: January to March 2006 large area of enhanced convection is expected Island group Rainfall outlook Outlook confi dence A from Vanuatu east southeast to Pitcairn Southern Cook Islands 20:30:50 (Above average) Moderate Island, including Samoa, Fiji, Tonga, Niue, and Vanuatu 20:40:40 (Near or above average) Moderate the Society and Austral Islands, where rainfalls Samoa 20:40:40 (Near or above average) Moderate are likely to be near or above average. The Fiji 20:40:40 (Near or above average) Moderate Southern Cook Islands is expected to experience above average rainfall. Tonga 20:40:40 (Near or above average) Moderate Niue 10:40:50 (Near or above average) Moderate Near or below average rainfall is likely from Society Islands 15:40:45 (Near or above average) Moderate Tuvalu east to the Marquesas Islands, including Austral Islands 15:40:45 (Near or above average) Moderate Tokelau, the Northern Cook Islands, and the Pitcairn Island 20:40:40 (Near or above average) Moderate Tuamotu Islands. Below average rainfall is Papua New Guinea 30:50:20 (Near average) Moderate expected over Western and Eastern Kiribati. Solomon Islands 30:50:20 (Near average) Moderate Near average rainfall is expected elsewhere in Wallis & Futuna 20:45:35 (Near average) Moderate the region. New Caledonia 35:35:30 (Climatology) Moderate Tuvalu 45:40:15 (Near average or below) Moderate The Southwest Pacifi c tropical cyclone season is well underway, although there have been Tokelau 45:40:15 (Near average or below) Moderate no occurrences to date. In both January and Northern Cook Islands 40:40:20 (Near average or below) Moderate February, risk increases, as there are usually two Tuamotu Islands 40:40:20 (Near average or below) Moderate to three tropical cyclone occurrences per month. Marquesas Islands 40:40:20 (Near average or below) Moderate About nine tropical cyclones can be expected Western Kiribati 50:30:20 (Below average) Moderate on average, for the complete season over the Eastern Kiribati 50:30:20 (Below average) Moderate entire Southwest Pacifi c region in ENSO–neutral NOTE: Rainfall estimates for Pacifi c Islands for the next three months are given in the table. The seasons similar to the present. The February tercile probabilities (e.g., 20:30:50) are derived from the interpretation of several global climate issue of the ICU will provide information on any models. They correspond to the odds of the observed rainfall being in the lowest (driest) one occurrences of tropical cyclones in the region. third of the rainfall distribution, the middle one third, or the highest (wettest) one third of the distribution. On the long-term average, rainfall is equally likely (33% chance) in any tercile. Rainfall outlook map for January to March 2006. Forecast validation: October to December 2005 nhanced convection, with average or above average American Samoa, and the Marquesas Islands. Suppressed Erainfall, was expected over Papua New Guinea and convection, or below average rainfall, occurred over the Solomon Islands, as well as from Samoa to central and Western and Eastern Kiribati, extending to Vanuatu and southern French Polynesia, including Niue and the Northern New Caledonia, as well as the Northern Cook Islands and and Southern Cook Islands. Suppressed convection was central French Polynesia. Rainfall was higher than expected expected over the equatorial region of Eastern Kiribati with in Tonga and the Marquesas Islands, and lower than forecast below average rainfall. Near or below average rainfall was in New Caledonia, Vanuatu, Wallis and Futuna, and the expected in Western Kiribati and Tuvalu. Near average Society Islands. The overall ‘hit’ rate for the October to rainfall was expected elsewhere in the region. December 2005 rainfall outlook was about 70%. Outcomes for the Solomon Islands (based on OLR anomalies) have Areas of average or above average rainfall affected Papua been consistent with forecasts for 11 consecutive months. New Guinea and the Solomon Islands, as well as Fiji, Tonga, Page 3 The Island Climate Update, No. 64, January 2006 Tropical Pacifi c rainfall – December 2005 Territory and December Long-term December Lowest on Highest on Records station name 2005 rainfall average (mm) 2005 percent record (mm) record (mm) began total (mm) of average American Samoa Pago Pago Airport 571.5 364 157 1966 Australia Cairns Airport 34.2 184 19 9 919 1941 Townsville Airport 57.6 131 44 0 458 1940 Brisbane Airport 120.2 126 95 30 438 1929 Sydney Airport 21.4 76 28 1929 Cook Islands Rarotonga Airport 104.4 188 56 11 653 1929 Rarotonga EWS 92.2 188 49 53 204 2000 Fiji Rotuma 330.8 285 116 27 664 1912 Udu Point 308.7 263 117 38 505 1946 Nadi 262.7 178 148 21 562 1942 Nausori 219.7 266 83 70 620 1956 Ono-I-Lau 44.2 149 30 9 523 1943 French Polynesia Hiva Hoa, Atuona 128.4 78 165 7 297 1951 Tahiti - Faa’a 280.4 268 105 20 759 1919 Tuamotu, Takaroa 120.8 192 63 31 540 1953 Gambier, Rikitea 426.7 202 211 36 440 1952 Tubuai 197.6 208 95 14 603 1953 Rapa 225.4 216 104 45 510 1951 Kiribati Tarawa 141.2 210 67 14 491 1946 New Caledonia Koumac 11.6 101 11 6 489 1951 Ouloup 50.8 138 37 4 391 1966 Ouanaham 17.4 154 11 18 613 1961 Poindimie 59.6 222 27 41 905 1965 La Roche 53.8 154 35 5 584 1956 La Tontouta 8.6 81 11 3 310 1949 Noumea 23.2 76 31 0 290 1863 Moue 6.8 125 5 12 630 1972 Page 4 The Island Climate Update, No.