From donsuntherland1 in the NYC forum.
The ECMWF weeklies had forecast temperatures to average above to much above normal across the region for the September 4-11 period. That forecast is verifying with the ongoing heatwave. September has increasingly become an extension of summer in parts of the Northeast. Since 2000, almost half of all years (48%) have had a monthly mean temperature of 70° or above in New York City. Prior to 2000, just 20% of Septembers had mean temperatures of 70° or above.
The ENSO Region 1+2 anomaly was +3.2°C and the Region 3.4 anomaly was +1.6°C for the week centered around August 30. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +3.22°C and the ENSO Region 3.4 anomaly has averaged +1.32°C. El Niño conditions will likely continue to strengthen into the fall with the current East-based event transitioning to a basinwide El Niño for the upcoming winter.
The SOI was -19.67 today.
The preliminary Arctic Oscillation (AO) was +0.527 today.
On September 7 the MJO was in Phase 3 at an amplitude of 2.665 (RMM). The September 6-djusted amplitude was 2.560 (RMM).
Based on sensitivity analysis applied to the latest guidance, there is an implied 76% probability that New York City will have a warmer than normal September (1991-2020 normal). September will likely finish with a mean temperature near 71.6° (2.4° above normal).