Review of Regional Weather for June 2023
1. Overview
rainfall was recorded over the ASEAN region. Over Mainland Southeast Asia,
above-average rainfall was recorded in the eastern parts of the region, while
a mix of below- to above-average rainfall was recorded over the rest of the
region. Over the Maritime Continent, above-average rainfall was recorded over
the western Maritime Continent, with a mix of below- to above-average rainfall
elsewhere. The largest positive anomalies were over northeastern Borneo for
both the GSMaP-NRT (Figure 1, left) and CMORPH-Blended (Figure 1, right)
satellite-derived rainfall estimates.1.2 The observed rainfall anomaly pattern of below- to
near-average rainfall over the ASEAN region is broadly consistent with the
predictions from the subseasonal weather outlooks for June 2023 (29 May – 11 June 2023</a >,
12 – 25 June 2023</a >
and
26 June – 9 July 2023</a >).
(left) and CMORPH-Blended data (right). The climatological reference
period is 2001-2022. Green colour denotes above-average rainfall
(wetter), while orange denotes below-average rainfall (drier).
1.3 Above-average temperatures were recorded over most of
Mainland Southeast Asia, with near- to above-average temperature over most of
the Maritime Continent. Near- to below-average temperatures were recorded over
the southern Maritime Continent. The warmest anomalies (more than 2 °C
above-average) were recorded over southern parts of the Malay Peninsula, Lao
PDR and northeast Thailand.
The climatological reference period is 2001-2022. Red colour denotes
above-average temperature (warmer), while blue denotes below-average
temperature (colder).
2. Climate Drivers
2.1 A Madden-Julian Oscillation (MJO) was active at the start
of June 2023. An MJO signal propagated eastwards from the Western Hemisphere
and Africa (Phase 1) and to the Indian Ocean (Phases 2 and 3) in the first
half of June. In Week 3, the MJO signal weakened and became insignificant. An
MJO signal re-emerged in Week 4 over the Western Hemisphere and Africa (Phase
1) and propagated eastwards to the Indian Ocean (Phase 2). Typically for June,
Phases 1 and 2 tends to bring drier conditions in northern Southeast Asia
while Phases 2 and 3 tend to bring wetter conditions to the western Maritime
Continent.
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 past month, there have been signs of El
Niño-like conditions. El Niño sea surfaces temperatures indices are near or
exceeding El Niño thresholds, whereas key atmospheric indicators (cloudiness
and wind anomalies) displayed neutral conditions for most of June.