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Subseasonal Weather Outlook and Review

Review of Regional Weather for February 2024

 

1. Overview

1.1 During February 2024, a mix of below- to above-average was recorded over the Maritime Continent, with parts of the western half of the equatorial region receiving above-average rainfall, and below-average rainfall elsewhere (Figure 1). Over Mainland Southeast Asia, near-average rainfall was recorded in February. The largest positive (wetter) anomalies were recorded over central Sumatra based on GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right) satellite-derived rainfall estimates. In contrast, the largest negative (drier) anomalies were recorded over central parts of the Philippines (in both GSMaP-NRT and CMORPH-Blended).

1.2 The observed rainfall anomaly pattern of above-average rainfall over the western and central parts of the equatorial Maritime Continent coupled with below-average rainfall in particular over northwestern Maritime Continent, and the near-average rainfall over Mainland Southeast Asia, are broadly consistent with the predictions from the subseasonal weather outlooks for February 2024 (5 – 18 February 2024 and 19 February – 3 March 2024).

era5_rainfall_anomalies
cmorph_bld_rainfall_anomalies
Figure 1: Rainfall anomalies for February 2024 based on GSMaP-NRT data (left) and CMORPH-Blended data (right). The climatological reference period is 2001-2023. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

 

1.3 Above-average temperatures were recorded over the Maritime Continent and much of Mainland Southeast Asia (Figure 2) in February 2024. The exceptions were over parts of Myanmar and Cambodia, where below-to near-average temperature was recorded. The warmest anomalies (more than 2°C above average) were recorded over some parts of eastern Thailand and southern Lao PDR.

era5_temperature_anomalies

 

Figure 2: Temperature anomalies for February 2024 based on ERA-5 reanalysis. The climatological reference period is 2001-2023. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

 

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) was active for much of February 2024, based on the RMM index (Figure 3). In the first and second weeks of February, an active MJO signal was present over the Western Pacific (Phases 6 and 7). In the third week of the month, the active MJO signal weakened in strength in Phase 7 and became e indiscernible in the last week of February. Typically for February, Phases 6 and 7 tend to bring drier conditions for 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 El Niño conditions over the equatorial Pacific continued weakening during February 2024. Sea surface temperatures in the Nino3.4 region (used to monitor ENSO) continue to show El Niño conditions but has likely past its peak, and key atmospheric indicators (cloudiness and trade winds) are consistent with the weakening El Niño conditions. El Niño events tend to bring drier and warmer-than-average conditions to much of the Maritime Continent during December – February.