Spring 2020
has been cold. The reason has been the
MJO, and the warm pool in the northeast Pacific. Before the very mild winter, November into
December 2019 was quite cold, the reason again was the MJO and that warm pool.
One thing I
want to point out, many times, cold Mays lead to early season tropical cyclone
activity in the western Atlantic and/or Caribbean. Historically years with cold Aprils and Mays
see increased odds of landfalling systems on the Gulf and East Coast of the
U.S. In my hurricane season outlook updates, I has been talking about how that could be a real problem for the Mid Atlantic and Northeast.
Summer solstice
will get here in 40 days, on June 20th. So, with April and so far in May, the
question is, will this Summer be cool as well?
Sea Surface
Temperatures:
The SSTs
have changed a lot from summer 2019 and even from winter 2019/2020.
The El Nino
Southern Oscillation (ENSO):
The ESNO is
a major driver when it comes to our weather pattern. It’s based on fluctuations
in the ocean and atmospheric temperatures in the equatorial Pacific. The ENSO is neutral when the SST in the
tropical Pacific are between -0.5C and +0.5C. El Nino is when the 3-month running average is
above +0.5C and La Nina is when the 3-month running average is below -0.5C
We’ve been
in ENSO neutral conditions (neither El Nino nor La Nina) since early Spring.
But, In the equatorial Pacific we’ve seen cooling developing. The SST anomalies
show the cooling on the surface and the subsurface.
Here is a
graphic from the IRI/CPC showing the model predictions for the ENSO.
The
Multivariate ENSO index (MEI)
The MEI has
shifted to slightly negative.
Based on the
look equatorial Pacific a La Nina is looking likely starting this summer. Other
outlets are saying the ENSO is going to stay neutral through the summer. But
based on my calculations and observations I think it will end up being a La
Nina. Looking at the sub-surface water temperatures we can see the surface is
cooling and the cool water rises. The surface SST should cool much more as cold-water
up-welling continues west of South America to the Date Line.
Historically,
Summers that experienced very warm temperatures, occurred during a shift toward
La Nina.
Large parts
of the Atlantic Basin are warmer than average
The warm
SSTs in the Gulf of Mexico and in the western Atlantic should help keep our
nighttime lows higher than average.
The seasonal
models:
CFSv2:
EURO:
JAMSTEC:
Soil
Moisture:
The Verdict:
Temperatures:
The
Northeast and Mid-Atlantic region can generally expect above average
temperatures from June through August. I think once the hot weather gets really
started, it is going to have some staying power.
June overall
temperatures should be average to slightly above average.
July will
end up quite warm in the Northeast and Mid-Atlantic, with temperatures
generally above average.
August will
be quite warm for much of the CONUS, with temperature anomalies here in the
Northeast and Middle Atlantic above average to well above average.
July and
August will be at least as warm as last year, in fact they could average 1-2
degrees warmer than July and August 2019.
The above average temperatures will stick around for the end of Summer into Fall 2020.
Precipitation:
This time of
year, much of our rain comes from thunderstorm activity. Later in the Summer there
will also be the possibility for impacts from tropical cyclones and tropical
rain. As has been the case for the last 5-7 years, this summer has a good
chance of being average to drier than average. But, that will depend on tropical activity, with the increased risk to the Northeast, Summer 2020 could end up being wet. But even if we see a wetter than average
summer, there is still going to be the possibility for dry or even drought
conditions in parts of the Northeast and Mid-Atlantic. So, while some areas
will see much less rainfall, others may not.
Remember, these warm temperatures should extend into Fall 2020.
That’s it
from me…….
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