OVERVIEW:  Our projection for September was maintained this week for a near to slightly above average (0.0°F to +2.0°F) temperature departure for the month as a whole. We are starting off the month above average, but an even mix of slightly above/below average and near average periods are expected over the remainder of the month to balance things a bit. October projections were officially introduced this week for a near average (-1.0°F to +1.0°F) temperature departure using long term climate guidance and global observation trends.

• Seasonal changes are going to be become more noticeable in the weeks ahead as we continue to lower average highs/lows, and that downward process accelerates beyond mid-September to about a 3.0°F drop per week. The extreme heat is likely behind us, but there will still be some warmer days yet that reach into the 80s up through about mid-September. Climate models have gone against the idea of a warmer start to October and are instead indicating a slightly cooler stretch for at least the first half of the month, and we have adjusted accordingly, and away from the warm-aggressive Euro/EPS weeklies.
   
• The Madden-Julian Oscillation (MJO) is currently temporarily in the Circle of Death (COD) or NULL phase, and largely remain there through much of September. In this case, the El Niño background state and other teleconnections will be running the pattern for awhile. Hurricane activity should remain limited with a strong El Niño increasing Atlantic shear despite approaching the peak of Atlantic hurricane season September 10th.

   

• A composite average of the SST departures in the ENSO regions places it in moderate to strong El Niño territory currently. From west to east across the Pacific, the Niño 4 (west-central Pacific) is currently the “coolest” region at +1.0°C, whereas the Niño 3.4 region (east-central Pacific) is currently at +2.7°C. The eastern regions of Niño 3 (east-central Pacific) is currently +3.5°C, and Niño 1+2 region (near the Peruvian coast) is at +4.2°C as of September 2nd. This is fairly close to last week’s observed values. The current El Niño Summer is likely to be followed by a strong El Niño Fall, and is currently East-based.

   

Average high temperatures are currently in the 79-83°F range from north to south across our coverage region, which is about 1-2°F lower than at this point last week, and also several degrees lower than the maximum climatological temperatures for the entire year. Temperatures will slowly drop off through early September, then the drop off accelerates downward beyond mid-month. Any above or below average stretches listed in the outlook will be relative to seasonal norms at that time, and it is important to note that cooler/warmer periods will be relative to the time of year we are talking about. For example, the transient slightly above average temperatures listed for the September 9th/10th period features highs in the lower 80s, coming at a time when average highs are in the upper 70s. Use the average highs/lows chart below providing transparency for what average temperatures are expected to be at each corresponding location through October 15th.

Our September projection was maintained this week for a near to slightly above average (+0.0°F to +2.0°F) temperature departure. October projections were officially introduced this week for a near average (-1.0°F to +1.0°F) temperature departure using long term climate guidance and global observation trends, and preliminary indications of a cooler first half of the month.