China Drought Persists as Hinnamnor Misses to the East; U.S. Drought Expansion

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Highlight: Hinnamnor to re-intensify to Cat-4, possibly a Cat-5 typhoon turning north and just-missing the China Coast. Immense California heatwave. Louisiana hurricanes in September. Midwest and Northeast drought expansion.

Fig. 1: Weather satellite view of the West Pacific and Category-4 Major Typhoon Hinnamnor.

Discussion: Departing the spring season, soil moisture across much of China was adequate to surplus. However, foreshadowed by record warm SSTA off the East Asia Coast, high-pressure formed and amplified through the summer season. The result? An incredibly rapid evolution of a super drought, one of the worst one record for East Asia. River beds have dried-up and immense water shortages and crop damage has occurred. The only way to break a drought this intense is inland migration of a weakening tropical cyclone.

Right now, we have Category-4 Major Typhoon Hinnamnor due east of Taiwan (Fig. 1) forecast to weaken slightly over the next day or two followed restrengthening as the storm turns north back to a category-4 major typhoon (some models have a category-5). The associated rainfall is immense but ECMWF indicates a near miss for China. Consequently, the super drought continues and intensifies (Fig. 2).

Fig. 2: ECMWF 10-day percent of normal rainfall forecast for China and vicinity.

In the North Atlantic tropics, the ECMWF identifies several issues over the next 10 days including an expected intensification of Tropical Disturbance 91L. The latest trend on 91L is a faster turn northeastward from east of the Bahamas early next week. This system could become a minimal hurricane by Sunday. 91L must survive the short-term shear pattern for development to follow.

The emerging next big weather story in the U.S. is the developing heat wave in California. The event is likely to last from 5 and up to 10 days in some areas. ECMWF indicates peak hot day in California is next Tuesday when the central and southern San Joaquin Valley reach 115-120F (Fig. 3).

Fig. 3: ECMWF projects the hottest day of the developing heatwave in California for next Tuesday.

Earlier this week, Climate Impact Company issued a week 2-5 outlook for the North Atlantic tropics which targeted the Gulf of Mexico for tropical cyclones the last third of September. In today’s updated 30-day probabilistic precipitation outlook, NOAA follows that lead with a high probability of heavy rainfall likely associated with tropical cyclones centered on Louisiana (Fig. 4).

NOAA updates their 30-day Drought Outlook which expands drought across southeast Nebraska, southern Iowa and into central Illinois (Fig. 5). The New England drought is forecast to expand into the northern Mid-Atlantic States.

Fig. 4: NOAA updates the 30-day precipitation outlook for September.

Fig. 5: NOAA updates the 30-day U.S. drought outlook valid for September.