Holiday weekend and Long Range Thoughts

Meteorologist , Steve Garry

When putting a forecast together you must know where you’ve been before you can predict where you’re going.

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The weather pattern is being driven by the very warm waters in the pacific ( +PDO ) which usually puts a ULL south of the aleutions,

and a ridge or building heights over the western u.s. and gulf of alaska. the atmospheric teleconnection to that ULL south of the aleutions

is a ULL over the Eastern US , which keeps northern tier states under the risk of frequent cold fronts and marine air masses.

We clearly have a basin wide Elnino event going on which is providing a very active sub tropical jet stream with tropical moisture

undercutting the ridge out west and moving into the southern plains with constant rain threats while interacting with the polar jet stream.

In the atlantic we clearly have a shift taking place from a +AMO to a -AMO with colder waters taking shape in the atlantic except for the western atlantic

which remains rather warm. This SST anomaly in

the atlantic is a signature for high latitude blocking or a -NAO feature.

We also have support from the stratosphere as the sun is going more quiet with very warm temperature anomalies due to a build up of ozone.

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The end result here is a -NAO or high latitude blocking pattern for north america

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With the Stratospheric warming and build up of ozone it is typical to have below normal 500mb heights over north america as the stratosphere compresses the

troposphere hence making it a cooler environment

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The ECMWF ensemble model guidance for 10 days out pretty much shows a trough or ULL over eastern north america , a ULL south of the aleutions

and above normal 500mb heights pushing deep into the arctic circle and north pole. A continued ridge out west and a active sub trop jet stream.

Bottom line if you are looking for a heat wave in the northern mid atlantic the chances are very low. The threat for wet periods of weather is also high due to

the convection around the date line ( 180 longitude) and an amplified polar jet stream.irtempanim_2

 

As far as the holiday weekend is concerned it will not be a washout but there will be a chance of shower or storm popping up during the afternoon.

These showers will be scattered to isolated in nature and temps will be slightly below to near normal , no holiday weekend record high temps this year.

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