Very Warm SSTA and Hot/dry East China Upper Ridge Risk Heading Into August

Highlight…Warm SSTA supports a dry/hot August ridge for China wheat-growing areas causing dry-to-drought conditions.

Discussion: The West Pacific SSTA pattern is possibly the warmest on record. The ocean surface is 5-15F warmer than normal just-off the central and northeast Asia coastline (Fig. 1). Consequently, expectations of a hot/dry upper ridge increase! Although not shown in the 10-day outlook, the “caveat forecast” provided by the mega-cluster ensemble indicates an aggressive Northeast Asia upper ridge pattern by days 11-15 (Fig. 2) which amplifies by day-15 (Fig. 3). The ridge would deliver hot and dry weather to East China wheat-growing areas. In August, the hot/dry risk indicated by ECM for the China wheat-growing areas is supported by the warm SSTA pattern and attendant upper ridge (Fig. 4-5). There is dryness in the China wheat-growing soil moisture likely to worsen during late meteorological summer. The warm SSTA also means typhoons reaching the Asia East Coast later this summer are likely to be stronger given the warm SSTA.

Fig. 1: West Pacific SSTA is exceptionally warm!  

Fig. 2-3: The mega-cluster “caveat” forecast of the upper air pattern across East Asia for days 11-15 and day-15.

Fig. 4-5: The ECM August temperature and precipitation outlook.