Warm Mid-latitude Oceans Bias Climate Warm

VERY Dynamic Pattern Across South America Drying Brazil

09/24/2023, 1:53 pm EDT

North Atlantic Basin 2023 Seasonal Activity So Far

09/26/2023, 9:12 am EDT

09/25/2023, 2:46 pm EDT

Fig. 1-3: Mid-latitude oceans are much warmer than normal and forecast models entrain that warmth and consistently forecast warm temperatures for the U.S.

Discussion: Certainly, a cooler pattern change can emerge at any time. However, the process of generating cooler pattern change is made more difficult by the much warmer than normal mid-latitude ocean surface (Fig. 1). The 12Z GFS keeps the warm bias in their forecast for the eastern ¾ of the U.S. (Fig. 2-3). The Gulf of Mexico remains clean of tropical cyclone risks in the midday 15-day outlook. The gas population weight HDD forecast into mid-October is extremely low while the population weight CDD forecast trends much warmer since last Friday maintaining a nationally warmer than normal pattern (Table 1 and 2).

Dates	HDD Forecast	12-Hr Change	24-Hr Change	30-Year NML	10-Year NML
Sep. 22-28	14.8	-0.6	-0.3	24.3	19.2
Sep. 29- Oct. 5	9.4	-6.1	-1.5	35.0	28.4
Oct. 6-12	25.6	-6.9	-4.5	47.9	39.3

Table 1: The 12Z GFS U.S. gas population weight HDD forecast compared to 12 and 24 hours ago.

Dates	CDD Forecast	12-Hr Change	24-Hr Change	30-Year NML	10-Year NML
Sep. 22-28	38.7	-0.2	+0.3	32.6	38.9
Sep. 29- Oct. 5	43.9	-1.8	+5.0	25.3	30.7
Oct. 6-12	33.4	+2.1	+3.5	19.3	23.8

Table 2: The 12Z GFS U.S. population weight CDD forecast compared to 12 and 24 hours ago.