Fig. 1-2: The 30-day and 90-day northern hemisphere upper air pattern which identifies the presence of a persistent trough over the North Atlantic warm hole.
Discussion: What is the North Atlantic warm hole (NAWH)? Since 2013, the NAWH pattern has strengthened due to accelerated presence of freshwater snow and ice melt from Northeast Canada and Greenland deposited into the Labrador Sea and eastward/southward most noticeable during MAY/JUN but generally present most of the year. During the past 10 years, the cool ocean waters have caused a cooling of the middle troposphere where a semi-permanent upper trough has generated. During the past 30 days, the trough has amplified off the Southeast Canada Coast and extended into the East U.S. (Fig. 1) bringing a cool late spring. Previously, the upper trough was mostly east of Newfoundland (Fig. 2). The NAWH pattern is vividly displayed east of New England and surrounded by the warming, typical of the past 2+ decades for the remainder of the North Atlantic (Fig. 3). The pattern is forecast to weaken and possibly reverse during the next 10 days allowing warmth into the East U.S. The NAWH upper trough is fierce, forecast models may be too strong with Northeast warming. Inevitably, the NAWH trough returns as indicated by the mega-cluster ensemble in 15 days (Fig. 4).
Fig. 3-4: The North Atlantic basin SSTA analysis reveals the region of cool waters associated with the North Atlantic warm hole and the day-15 upper air forecast indicating the return of the NAWH trough over New England.
The U.S. gas population weight CDD forecast trends cooler (again) for next week and is firmly below the 10-year and 30-year climatology (Fig. 5). The June 2-8 forecast is slightly warmer and near normal.
Fig. 5: Latest U.S. population weight CDD forecast utilizing all models, their consensus, and comparing with 24 hours ago and climatology.