Monday, October 29, 2007


Well much of the Delaware Valley received there first frost of the season last night. Some of the colder suburbs in Southern and Central NJ and Eastern PA, will likely see another frost for tonight, as temps in the colder suburbs dip to the low and mid 30's.

I've got into a heated debate over what a true pattern change really is, and what We've experienced with the rain and cooler temps (Near Avg) was nothing more than a cut off Upper Level Low spinning in the Tenn/Valley and a cool High Pressure off the NE coast, causing a baroclinic zone/Overrunning, and an avenue for tropical moisture to stream northward between the systems for a few days. This ULL then moved into Eastern Canada over the weekend after being stalled out for a few days, and phased with the Northern Stream, which remained to the north.

As this ULL phased in with the Northern Branch, it pulled the Northern Jet SE ward into the NE, thus a trough for a couple days and CAA. This is why we are getting cooler temps. But this trough rotates out and the pattern flattens back out. We will begin to warm up this week as a SW flow aloft develops. Temps will approach the Upper 60's to near 70 on Wednesday, so about 7 to 10 Degrees above avg. Overall this week should average slightly above normal.

Now let's talk about "A REAL PATTERN CHANGE"

As we all know this month has been a real blowtorch in the east with record warmth and A persistant pattern. There's been a strong Pac Jet, and GOA Low in place for much of the month. This has maintained the jet to be more zonal into the Northern US and Southern Canada, holding the Northern Branch at bay for quite a while. Also we also had a strong SE Ridge, which has helped pump the warm air into the east. The combination of this and Pacific air, resulted in very warm and dry conditions. The only thing I've see that's really changed, is the SE Ridge was kicked out by the ULL low and a brief visit of the Northern branch with a shot of seasonably cool air. Guys this is Not a pattern change, Temporary at best, because we return to warmer conditions and a SW or zonal flow in the upper levels. Not blowtorch warmth only because the SE Ridge is Gone !

Everything is once again transient, in and out, I spoke clearly about this for my second half of October forecast. There have been some changes over the past week in the Pacific signal, but please understand these change take time to transpire here in the east and downstream.

So now we can talk about the changes to take place between the 5th of November and possibly into the mid-month timeframe (about a 2 week period Minimum)

The slow changes now taking place in the Pacific are as follows. The Pac Jet is now relaxing some and not as strong. As I mentioned before this once strong flow blasted the Jet East, rotating around the H5 GOA low, and ejected this flow eastward into the Northern US, and Southern Canada, thus holding the Northern Branch at bay. In addition to the Pac Jet is now relaxing, The GOA, H5 low has diminished and is repositioning itself, and retrograding Northwestward to more of an Aleutian Low. This will pump a ridge into Western Canada, and allow the Northern branch to plunge southeast into the US. This then teleconnects a trough in the central and Eastern US, as we approach the 5th of November. This trough will then have a much better chance to stick and become a more permanent feature, and not just transient. The SE ridge being squashed, will also aid in the allowance of all this to come together.

The overall result will be a Colder Pattern with near and below normal temps, in the Central and Eastern US, between the 5th and 15th of November. Most of all, the Northern branch will be free and make it's charge (Something We haven't seen in the East, A carved out deep trough that sticks for a week or so, and bring cold air down from Canada.) Sorry but IMO an ULL that manufactures it cold air, and brings it down to the surface (near to slightly below normal temps) in a select region, for a few days, is not a pattern change. A transient trough resulting from that ULL pulling NE into Canada and bringing a 2 day shot of Near avg cold, Is not a pattern change. Milder air and above normal temps following for this week, is not a pattern change.

The pattern change will likely take place and be around the 5th of November. This then lasts into around mid month. This my friends is a True Pattern change, and the results will be a trough in the Central and Eastern US for a 1 to 2 week period, along with colder and stormier conditions, during this time. The details with these change will be discussed as we approach that timeframe.

The bottom line is this: IMO and please respect it, If there's no upper level support for more than a week or two period, it's not a Full pattern change ! The Northern Branch has not been involved or carved out any large trough anywhere in the States to this date. Temps have not reversed, just went to near normal values from now until tomorrow, then we warm to above normal for a few days, then back to normal towards the weekend. These are seasonal conditions or a normal stepdown of the seasons.

Because we get rains for a few days caused by the factors I alluded too, and go from much above to normal, is nothing more than what it should be. Remember this guys, we were very fortunate to get much needed rains and closer to normal contitions from last weeks setup, it was all together a regional event. Upper level lows do this, when they become cut off or undercut the mainstream, not a true pattern change IMO, because it's all regional.

Take Care,

1 comment:

Denise said...

I do read it eeveryday, just remember the colder it gets the more snuggling, hugging and HUMMMMM happens.

With all my love