During late spring to early summer (May–June), the South Asian High (SAH) migrates northwestward from the Indo-China Peninsula to the Tibetan Plateau, actively interacting with South Asian convection. Convection over the western flank of the SAH track releases latent heat and excites an upper-level anticyclonic anomaly to its northwest, promoting the SAH’s northwestward movement and intensification. Meanwhile, the upper-level divergent pumping of the SAH over its eastern flank favors the development of low-level convection.
The SAH migration pathway exhibits pronounced interannual variability. K-means clustering of pentad-mean SAH tracks for 1958–2020 reveals four major types: fast-westward track (FT), slow-westward track (ST), northward track (NT), and west track (WT). In FT type, the SAH accelerates westward from mid-May to June, reaching the Tibetan Plateau with zonal oscillation. The ST type display that the SAH moves westward slowly and reaches at the Tibetan Plateau by late June. The NT type witnessed that the SAH shifts predominantly northward, remaining over the northern Indo-China Peninsula through June. In the WT type, the SAH exhibits monthly mean positions significantly west of the climatology in both May and June.
The FT and ST types are closely linked to intraseasonal convective variability. Enhanced (suppressed) convection over the west of the SAH’s track accelerates (decelerates) SAH westward movement. These convection anomalies propagate eastward and coincide remarkably with the eastward-propagating Madden–Julian Oscillation (MJO). As the enhanced convection reaches the eastern flank of the SAH, the SAH’s upper-level divergence further strengthens the convection; conversely, suppressed convection weakens over the eastern flank of the SAH. This interaction between MJO-related convection and the SAH yields fast or slow westward migration and modulates the convective intensity during eastward propagation.
In contrast, the NT and WT types are governed by monthly mean convection anomalies. A dipole pattern of upper-level geopotential height anomalies over South Asia, triggered by an eastward-propagating wave train from Europe, induces opposite convection anomalies between northern India (west of the SAH track) and the South China Sea–southern China region (east of the SAH track). In the NT type, suppressed convection over northern India, associated with a cold low-pressure anomaly, hinders westward displacement and favors northward movement of SAH, with enhanced convection over South China Sea–southern China region. In the WT type, enhanced convection over northern India, accompanied by a warm high-pressure anomaly, promotes a westward-shifted SAH, with suppressed convection over South China Sea–southern China region. The upper-level dipole is maintained through a positive feedback between the anomalous circulation and convective heating, with the SAH’s altered upper-level divergence further shaping the downstream convection.
These findings highlight multi-scale interactions between SAH movement and South Asian convection, where MJO and extratropical wave trains drive distinct pathway types. The results offer insights for improving sub-seasonal to seasonal prediction of the Asian summer monsoon.
 

South Asian High,pathway clustering,Madden–Julian Oscillation