Major soaker for the Northeast on Friday???

Good evening everyone and happy hump day :)

So what gives , early in the week the models advertised a pretty good soaking coastal low pressure to impact the region from DC-Boston.

The whole synoptic weather pattern favored and still does by the way for this type of scenario to come to light.

We have an active sub tropical jet stream , we have trough over the eastern united states , and we have our famous -NAO.

Not to mention plenty of convection around the dateline in the pacific(which is a precursor to stormy weather conditions on the east coast)

So what gives? , why all of a sudden the models shifted the storm further east OTS (out to sea) and missing a large part of NJ , PA , & NY?

Whether it is the summer , fall , winter , spring  , snowstorm , rainstorm there has to be a specific standard for a benchmark storm.

What is a benchmark storm? a storm that passes over 40 N and 70 W that gives areas like DC to boston a pretty good precip event.

500mb_sf

I want you all to look at our disturbance( the storm) , focus on the number 5880 and how that line dips. that right there is our storm.

here is the 500mb PVA image depicting the same idea

ECMWF_500mbHgtVort_na_f3

focus on the number 588 , and that yellow right above it , that is the short wave trough that will produce the coastal storm on friday.

Very important here , is the orientation of this trough  , and by that i mean how does it tilt ( positive or negative ?) the orientation of this trough is clearly from northeast to southwest or a positive tilted trough.

this trough axis btw a few days ago was not this positively tilted , hence the storm riding up very close to the coast.

what you would like ideally is the trough axis to become neutral or slightly negative around the mississippi river valley and negative tilt just before the coastline.

here is the latest euro image from today at 18Z thursday

ECMWF_500mbHgtVort_na_f30

notice how the trough is still positive tilted and does not go neutral until it is over about georgia

ECMWF_500mbHgtVort_na_f45

by this time it is too late for the storm to ride over the benchmark that i had mentioned above as the trough does not go negative until off the coast

ECMWF_500mbHgtVort_na_f63

by this time most of the energy and the storm is focused off shore to have any effect on areas like eastern PA or NYC , most of long island.

 

SO WHAT CAN GO WRONG HERE?

Well the short wave energy can unexpectedly and suddenly go into a neutral / negative axis and effect a good part of the northern mid atlantic / northeast with heavy rainfall.

This is not however anticipated but can happen , so we need to keep eye on this short wave trough.

A very tricky forecast as it stands right now for extreme eastern LI , All of the cape and ME as latest euro models has it backing a bit further west than previous few.

At this time expect heavy rainfall for DC , DELAWARE , AND EXTREME SO JERSEY

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UPDATES ON COASTAL STORM AS NEEDED

Meteorologist Steve Garry

 

 

 

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