Floods in February 2023

4 June 2024

Floods in the Philippines – Invest 99W – Feb 2023

Online reports show the precipitation intensity and impact during this period. They are available at :

AHA center and on floodlist websites.

Let’s focus on event number 2 on the AHA weekly report. Figure 1 shows the daily rainfall estimation.

Figure 1 – Daily rainfall estimation on (a) 17 Feb and (b) 18 Feb 2023 – source JAXA GSMAP
Figure 2: MISVA filtering products based on ecmwf – Precipitable water anomalies (shading), 850hPa wind anomaly (barbles) analysed on 18 Feb 2023.

Figure 2 shows the anomalies of PW and wind at 850hPa. Over the Philippines, the anomaly provided by the sum of the waves (b) is very similar to the total anomaly (a). It means that the weather pattern – high moisture content and a cyclonic circulation – is mostly explained by the superposition of the waves. On 18 February, ER (c), MRG (d) and TD-like (e) waves all contributed to the moisture and vorticity supply.

Floods in Malaysia – Feb 2023

Two documents can be consulted to assess the impact of extreme rainfall on this case study. They are available at :


Figure 3: Pentad rainfall estimation on 1st March 2023 – source JAXA GSMAP

A cold surge had reached the South China Sea. Red level warning was issued by METMalaysia.

Figure 4: MISVA filtering products based on ecmwf – Precipitable water anomalies (shading), 850hPa wind anomaly (barbles) analysed on 28 Feb 2023.

A widespread heavy rain event resulted in severe floods (Fig. 3). MISVA filtering products (Fig. 4) show a moist envelope of ER wave and MRG wave

That came on top of the low frequency typical of la Nina with enhanced northeasterly monsoonal flow and lots of moisture.

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