March was pretty well forecast....I was all over the blocking head fake from the composite, which I fell for last year. Not this year....I knew it would hold off until April.
March 2021 Review
Teleconnections
Following the deviation from the forecast in February, owed to the mid winter Sudden Stratospheric Warming protracting the blocking from the first half of the season, March has gone essentially according to plan. Any residual high latitude blocking relinquished its grip by mid February, paving the way for a very benign and unremarkable weather pattern across the region. The supposition from the winter outlook was that the reemergence of blocking during the month of March, which was implied by the forecast composite, would materialize more slowly than forecast and likely be delayed until April, much like last season. This assertion was based on both the +QBO, as well as the proclivity for moderate or stronger la nina events to truncate the winter season.
This forecast assertion as proved correct, as the polar domain remain relatively hostile to sustained winter weather for the vast majority of the month.
As evidenced in the annotation above, some degree of blocking does look to reestablish itself during the month of April. This likely would have happened sooner had the la nina remained weaker, and/or the QBO were less resistant to high latitude blocking. Another implication of la nina remaining at moderate intensity into March is that the RNA pattern did not relinquish its grip as much as it could have if the cool ENSO event had either remained weak, or weakened at a faster rate.
Although the largely hostile polar domain and the lingering la nina did lead to relatively mild and quiet month of March with a great dearth of snowfall, it was not exotically warm in the mean, given that Aleutian ridge did indeed extend more poleward this month, as forecast.
Composite Verification
Here is the H5 composite for the month of March 2021:
Actual March 2021 H5 Composite
Note that while lower heights were prevalent both across the higher latitudes, as well as the western CONUS, the Aleutian ridge did extend more to the NW and poleward, as forecast.
Eastern Mass Weather March 2021 Forecast H5 Composite
This acted to partially negate the modifying influence of the lower heights across higher latitudes and the the western US, which resulted in approximately a +1F monthly departure from the mean across the region.
Actual March 2021 Temp Anomalies
This was near the higher end of the forecast range for near normal monthly departures.
Eastern Mass Weather Forecast March 2021 Temp Departures
Finally, the month features below average precipitation, which worked in concert with the slightly above average temps to leave the region essentially void of monthly snowfall.
Actual March 2021 Precip Anomalies
These dry conditions were also congruent with the forecast expectations from last November for month of March.
Eastern Mass Weather March 2021 Forecast Precip Anomalies
The complete forecast review for the entirety of the winter 2020-2021 season will be issued in May.
