Old man winter decided to not show for the winter of 2019-20 not just over the USA but the majority of the hemisphere. Now that we’re well into spring when heat, storms and even hurricanes become the focus, winter decided to arrive, albeit 2 months late. With a shift in the big tropical drivers, the chill is likely to continue over the Lower 48 through much of the rest of April.
The big contributor to perhaps the warmest US winter on record likely can be mostly attributed to the warm lag effect of the Super El Nino and the stored up warmth within the tropical oceans. This stored up warmth over the west equatorial Pacific helped drive a warm phase 6, 7 and 8 of the MJO which forced a strong ‘mid’ Pacific high, deep Aleutian low and extended jet stream in between. This stronger zonal jet forced warm ocean air across the continent.
With a seasonal shift and push into phases 8, 1 and 2 of the MJO, ridging has finally developed up over Alaska, forcing a -AO/NAO for the first time since last November. Unfortunately this setup leads to a chilly April for the Lower 48 and it looks like we’ve a significant mid to late April cold spell for the central and eastern US not just this week but through much of the rest of the month.
The below GFS ensembles have a near perfect ‘winter lovers dream pattern’ at a time when you don’t want it…
Credit: Tropical Tidbits
6-10 day
Credit: Tropical Tidbits
The 5-day mean temperature anomaly is significantly negative for the time of year…
Here’s the 2m temperature anomaly for the upcoming 5 days!
Credit: Tropical Tidbits
Credit: Tropical Tidbits
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