Right off the bat, we’ll start with a tropical signal spreading across the northern hemisphere by observing the MJO with a hovmoller. Apparently shown, we have another signal in line with the Maritime Continent, coming from the Indian Ocean. Below, I have attached MJO composites that are also consistent with the background state of ENSO, which we remain entrenched in the La Nina state. By taking this large-scale approach and aligning it with composites and guidance, we were able to get an overall sense of how this pattern should play out when we April start!
Not surprisingly, for any convection signal traveling from the Indian Ocean into the Western Pacific, this means warmer east, cooler west. This shows up quite nicely in composites for stages 5 and 6! Let’s dive into some of the things bands are showing as we head into mid-April.
As we move into the first week of April, we see the trenches continue to deepen to the west, with rippling lines attempting to billow east of the Appalachian Range. Note, the active Pacific Ocean continues without containment at high latitudes. This is reflected in the upper-stage jet stream with a remarkable pattern of activity digging west of the Rockies with an active subtropical arm clearly developing. Literally a model that favors extreme weather flares, especially in the absence of containment because it can directly impact moisture returning from the bay by bringing in cold fronts down 48 degrees lower.
This will also allow for more warm-up, although still progressive in nature, east of the Rockies with more of a sense of spring in the air and unobstructed blooming vegetation, especially on throughout the South and Southeast.
We do, however, see a return of lockdown across Greenland, which is valid given the lingering effects from the stratospheric warming event in early February (yes, this could drag on). up to 60 days after warming with continued “drip” into the troposphere). What also makes it more legit is the way it regresses to the west. This would then force the polar current to the south, causing more risk of cold into the sub-48 region and bringing more widespread mean temperatures below average, especially east of the Rockies.
We see this reflected in the 2 meter temperature anomalies for the first 7-14 days, where we see a cooler west, a warmer east. This then translates to cooler and more widespread air masses, which will also temporarily limit episodes of extreme weather. So going back to when I discussed in mid-March that the pattern is not necessarily a “hit and hold” pattern, here for April it seems more or less the same, given the nature of the pattern. transients of the pattern although more prolonged in terms of cooler and warmer air masses for the lower 48 upper regions.
About the author
Hello! My name is Armando Salvadore and I am a Mississippi State graduate with a Bachelor of Professional Meteorology and an Activity Meteorologist working in the Private Sector. Stay tuned if you like technical, exotic, and general weather tweets! Also big on long-range forecasting as well! Twitter: @KaptMands