What's causing this cold rainy low to sit isolated over the Great
Lakes for days, instead of moving somewhere else?

With that much activity, you'd think it would wander off.

When it rains for days and nothing's moving, that's another matter,
but this one is actively staying put.
--
Ron Hardin


On the internet, nobody knows you're a jerk.

Ron Hardin wrote:
What's causing this cold rainy low to sit isolated over the Great
Lakes for days, instead of moving somewhere else?

How long has ben like that and do you have a link preferably with
archived stuff?

Weatherlawyer wrote:

Ron Hardin wrote:
What's causing this cold rainy low to sit isolated over the Great
Lakes for days, instead of moving somewhere else?

How long has ben like that and do you have a link preferably with
archived stuff?

It's been over Ohio for 3 days, but was over Chicago well before that,
and it's still there too.

Click on an animated radar map somewhere and you can see it circle,
westward in the north and eastward in the south, just round and round,
and it's been doing it for days.

I've just been watching it on wunderground.com , which only has
current weather.

--
Ron Hardin


On the internet, nobody knows you're a jerk.

On 14 May 2006 20:55:50 -0700, "Weatherlawyer"
wrote:


Ron Hardin wrote:
What's causing this cold rainy low to sit isolated over the Great
Lakes for days, instead of moving somewhere else?

How long has ben like that and do you have a link preferably with
archived stuff?

some stuff

http://radar.weather.gov/ridge/Conus/full_loop.php

On Sun, 14 May 2006 23:43:28 GMT,
Ron Hardin , in
wrote:
+ What's causing this cold rainy low to sit isolated over the Great
+ Lakes for days, instead of moving somewhere else?

It is cut off from the normal mid-latitude flow in the upper levels,
so it sits and spins.

http://weather.unisys.com/upper_air/ua_500.html

You can go back thru the previous 72 hours and see a very slow
west-southwest motion. You can see there is a split flow occuring over
the Canadian prairie provences. The good news is that the low looks
like it is about to get picked up by the southern branch of that flow.

If so, it'll probably exit the CONUS over North Carolina/Virginia.

http://www.srh.noaa.gov/fwd/glossary/def/cutofflow.htm

--
Consulting Minister for Consultants, DNRC
I can please only one person per day. Today is not your day. Tomorrow
isn't looking good, either.
I am BOFH. Resistance is futile. Your network will be assimilated.

I R A Darth Aggie wrote:
On Sun, 14 May 2006 23:43:28 GMT,
Ron Hardin , in
wrote:
+ What's causing this cold rainy low to sit isolated over the Great
+ Lakes for days, instead of moving somewhere else?

It is cut off from the normal mid-latitude flow in the upper levels,
so it sits and spins.

snip

I believe a strong high over the Maritime Provinces of Canada/Greenland
is also responsible for blocking the upper flow, and the situation is
termed a "Rex block":

http://www.theweatherprediction.com/habyhints/178/

And, unfortunately for those of us in New England, this pattern is
likely to continue. From

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

BLOCKING PATTERN CONTINUES IN MEDIUM RANGE DAYS THREE THROUGH
SEVEN WITH PERSISTENT NEGATIVE ANOMALIES WITH CLOSED MID-UPPER
LOWS OVER THE GREAT LAKES/NEW ENGLAND AND NEAR 45N 140W OVER THE
NORTHEAST PACIFIC.
THE POSITIVE HEIGHT ANOMALIES ARE OVER THE INTERMOUNTAIN
WEST/GREAT BASIN AND WEST TO EAST FROM SOUTH AK ACRS NORTHERN
CANADA TO GREENLAND.
OVERALL PATTERN FAVORS COOLER THAN NORMAL CONDS ACRS THE GREAT
LAKES-NEW ENGLAND AND WARMER THAN NORMAL AND DRY ACRS MOST OF THE
WEST.

Mike

Charles wrote:

some stuff: http://radar.weather.gov/ridge/Conus/full_loop.php

What exactly is that showing me?

http://www.weather.org.uk/charts/thumbs.html shows a rather active
series of forecasts portraying the life of a Low that has dwelt off in
the Norht Atlantic for a very long time now.

The life cycle of these things is that they move out east from
Newfoundland and broach at Scotland or Norway but as you can see this
cycle seems capable of regenerating itself despite all the occlusions
it is sending ashore.

It is unusual enough that it is imitating the Azores high. (Cyclones do
tend to hang out off Iceland if there is some sort of a block going
on.) This one seems to be waiting for a certain volcano to blow its
stack.

(I wonder what's keeping these people from publishing a time and date:
http://english.aljazeera.net/NR/exer...B9F79586F1.htm
)

I R A Darth Aggie wrote:

On Sun, 14 May 2006 23:43:28 GMT,
Ron Hardin , in
wrote:
+ What's causing this cold rainy low to sit isolated over the Great
+ Lakes for days, instead of moving somewhere else?

It is cut off from the normal mid-latitude flow in the upper levels,
so it sits and spins.

http://weather.unisys.com/upper_air/ua_500.html

You can go back thru the previous 72 hours and see a very slow
west-southwest motion. You can see there is a split flow occuring over
the Canadian prairie provences. The good news is that the low looks
like it is about to get picked up by the southern branch of that flow.

If so, it'll probably exit the CONUS over North Carolina/Virginia.

http://www.srh.noaa.gov/fwd/glossary/def/cutofflow.htm

Would it be more correct to say that the low _is_ the cutting off of
upper level winds?

The idea would be that a strong enough low produces a stream function that
includes cutting off of upper level winds.

The philosophical problem (as to causality) is that the stream function is
something of a fiction, as is, as a result, identification of the ``same''
wind.

So the problem is then how to decide if a low is one of the lingering
variety or not, since obviously most lows are carried along and move out.

What I remember from 2d imcompressible flows long ago, is that same-sign
rotations attract and differing-sign rotations repel, as to dynamics. As
well, of course, as simply adding some constant velocity to everything causes
everything to drift that way, which seems to be the usual drift causality.

For some reason, then, the constant went to zero. Perhaps it is part of some
very very large scale vortex over which the ``constant'' serves as a constant?

I'm not sure how to do causality in fluid flows, in short.
--
Ron Hardin


On the internet, nobody knows you're a jerk.