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Subseasonal Weather Outlook and Review

Review of Regional Weather for February 2022

 

1. Overview

1.1 During February 2022, the Maritime Continent experienced a mix of below- to above-average rainfall. Mainland Southeast Asia experienced a mix of near- and above-average rainfall relative to its typical dry season, with above-average rainfall over much of Thailand, Cambodia, northern Lao PDR and northern Viet Nam (Figure 1). Both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended) show large positive anomalies (wetter conditions) over the Malay Peninsula and northern Sumatra, and large negative anomalies (drier conditions) over Java Island. There are some discrepancies between the two datasets, as CMORPH-Blended (Figure 1b) recorded below-average rainfall for much of Borneo and southern Sumatra, while GSMaP-NRT (Figure 1a) recorded near- to above-average rainfall with isolated areas of below-average rainfall over the mentioned region.

1.2 The above-average rainfall for the western Maritime Continent and mixed below- to above-average rainfall for much of the rest of the Maritime Continent is in line with much of the subseasonal weather outlooks for February 2022, which overall predicted above-average rainfall over the region around the Malay Peninsula and southern Thailand (24 January – 6 February, 7 – 20 February, and 21 February – 6 March). The exception is over the Philippines, where above-average rainfall was predicted during February, whereas Figure 1 shows the country experienced a mix of below- to above-average rainfall.

era5_rainfall_anomalies
cmorph_bld_rainfall_anomalies
Figure 1: Rainfall anomalies for the month of February 2022 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2021. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

 

1.3 A mix of below- to above-average temperature was recorded in Southeast Asia in February 2022, with below- to near-average temperature recorded over much of Mainland Southeast Asia and the Malay Peninsula, above-average temperature over much of the Philippines, southern Viet Nam, and southern Sumatra, and near-average temperature recorded elsewhere (Figure 2). The largest negative anomalies (more than 2°C cooler) were over northwestern and northeastern parts of Mainland Southeast Asia.

era5_temperature_anomalies

 

Figure 2: Temperature anomalies for the month of February 2022 based on ERA-5 reanalysis. The climatological reference period is 2001-2021. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

 

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) signal was indiscernible at the start of February 2022, based on the MJO phase diagram below (Figure 3). In the second week of February, an MJO signal developed over the Indian Ocean (Phase 2). The MJO signal then propagate eastward over the Indian Ocean to Phase 3, before weakening and becoming indiscernible in the last week of February. Phase 2 tends to bring drier conditions to the southeastern Maritime Continent while Phase 3 tends to bring wetter conditions to the western Maritime Continent.

mjo_phase_diagram

 

Figure 3: The MJO phase diagram. The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator (denoted in the text with the first day of the month in blue and the last day of the month in red). The distance of the index from the centre of the diagram is related to the strength of the MJO. Values within the grey circle are considered weak or indiscernible (data from the Bureau of Meteorology, Australia).

 

2.2 Over the tropical Pacific Ocean, La Niña conditions were present. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) and the atmospheric indicators over the tropical Pacific Ocean were consistent with La Niña conditions. La Niña events tend to bring wetter-than-average conditions to much of the Maritime Continent during the December to February period.