Review of Regional Weather for March 2022
1. Overview
1.1 During March 2022, above-average rainfall was recorded over much of the northern ASEAN region, while a mix of below- to above-average rainfall was recorded over the southern ASEAN region (Figure 1). For the northern ASEAN region, above-average rainfall was recorded apart from over central and northern Myanmar. The largest positive anomalies (wetter conditions) were recorded over northeastern Mainland Southeast Asia and southern half of the Philippines for both satellite-derived rainfall estimates datasets (GSMaP-NRT and CMORPH-Blended), which was associated with tropical depression 01W that formed on the last three days of March 2022. For the southern ASEAN region, negative anomalies (drier conditions) were recorded over western parts of Sumatra as well as western and central Borneo, although the negative anomalies were larger based on CMORPH-Blended data (Figure 1b) compared to GSMaP-NRT (Figure 1a). Elsewhere in the southern ASEAN region, rainfall tended to be near- to above-average during March 2022. There are some discrepancies between the two datasets, as GSMaP-NRT recorded above-average rainfall for much of central Java and northern Sumatra, while CMORPH-Blended recorded near- to below-average rainfall with isolated areas of above-average rainfall over the mentioned regions.
1.2 The observed rainfall anomaly pattern of above-average rainfall for much of the northern ASEAN region and a mix of below- to above-average rainfall for the southern ASEAN region is broadly consistent with the predictions from the subseasonal weather outlooks for March 2022 (21 February – 6 March, 7 – 20 March, and 21 March – 3 April).
1.3 Most parts of Southeast Asia north of 15°N experienced above-average temperatures during March 2022 (Figure 2). The largest positive anomalies (more than 1°C warmer) were over northern and eastern parts of Myanmar, northwest Thailand, northern Lao PDR and northern Viet Nam. Elsewhere, near-average temperatures were experienced in most of the region, with above-average temperatures for Papua and southern and central parts of Sumatra, and below-average temperatures for parts of the southern Mainland Southeast Asia.
2. Climate Drivers
2.1 The Madden-Julian Oscillation (MJO) signal was indiscernible at the start of March 2022, based on the MJO phase diagram below (Figure 3). In the second week of March, an MJO signal developed over the Western Hemisphere (Phase 1). The MJO signal then propagate eastward over the Indian Ocean (Phase 2 to Phase 3), before weakening and becoming indiscernible in the last week of March. 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.
2.2 Over the tropical Pacific Ocean, La Niña conditions were present but there are signs of weakening. 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 March period.