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
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.