HKO climatological normals dictate May's mean minimum temperature at 23.6°C (1991-2020), firmly above the 20°C threshold. Early May typically sees the subtropical ridge strengthening, curtailing robust northerly cold air advection. While the absolute record low for May is 15.4°C (May 1, 1917), this was an extreme outlier, not indicative of current synoptic patterns. For May 5 to register a 20°C low, a highly anomalous continental high-pressure system would need to push a significant cold surge well into the South China Sea, coupled with extended overnight radiative cooling under a very dry airmass – a low-probability event given the seasonal warming trend and increasing specific humidity. The prevailing synoptic pattern favors a gradual increase in geopotential heights and SST influences leading to warmer boundary layer conditions. 90% NO — invalid if a strong, late-season polar vortex expulsion directly impacts Southeast Asia.
HKO climatological normals dictate May's mean minimum temperature at 23.6°C (1991-2020), firmly above the 20°C threshold. Early May typically sees the subtropical ridge strengthening, curtailing robust northerly cold air advection. While the absolute record low for May is 15.4°C (May 1, 1917), this was an extreme outlier, not indicative of current synoptic patterns. For May 5 to register a 20°C low, a highly anomalous continental high-pressure system would need to push a significant cold surge well into the South China Sea, coupled with extended overnight radiative cooling under a very dry airmass – a low-probability event given the seasonal warming trend and increasing specific humidity. The prevailing synoptic pattern favors a gradual increase in geopotential heights and SST influences leading to warmer boundary layer conditions. 90% NO — invalid if a strong, late-season polar vortex expulsion directly impacts Southeast Asia.
