November 30 Winter Potentials

This is posted late but this was posted on the Accu Weather forums on the 29th already....
Overall I think it was a pretty accurate forecast....As far as here in Allentown PA ...we made it to a high temp of 37 degrees which was about 7 degrees colder then forecasted and ended up with 0.3 inches of snow as well as sleet and some freezing rain.
This all taking place in the month of November which started out warm and above normal with temps as high as 70.
However...the cold arrived as thought it would and overall the month ended in a negative departure of 1.1 (as of the 29th) ....

This is something that i had forecasted back in March of 2008 for the month of november. Verification will be posted tomorrow for the overall departures....

November 26th Weather Discussion

November 26th Weather Discussion

I apologize to all the readers of this blog but I am only able to update this on a daily basis when I have off from my employment. .

Today is going to continue with the trend of temperatures being below normal. Daytime highs will be in the upper 30s to lower 40s across south central PA into east central PA and the Northern New England coastline...Further inland temperatures will be in the mid to upper 30s. Along the southern New England coast into NJ ...lower to mid 40s. South of the PA/MD border mid 40s to around 50. The mountains of WV look like the mid 20s.
Weather wise we should expect mainly cloudy skies however around SE PA look for breaks in those clouds. The rest of PA(north and west of Allentown) into NY look for snowshower to continue from the upper level low across Northern NY...Further north into Northern new england will be rain along the coast to a mix interior and snow to the north of that......

November 24-25th Weather

1-3 inches for the light blue..However this does not take into account the mountains of NY and mountains of PA above 2000 feet. Those locations in NY could get upwards of a foot of snow. The mountains in PA could get upwards of 6 inches...

The pink area will be a mix zone of rain, sleet and snow where a combination could occur at any given time but should change to all snow after 1 AM...

The green is rain where anywhere from .50 to an inch can occur except in NY where those amounts can exceed an inch.....this are of green can end as snowshowers.

Of course the areas that are blank are a no forecast zone

Discussion
So heres what I think is going to occur in eastern PA...

Precipitation should hold off to coming in to around 7 pm or after 7 PM and should start as rain or a mix of rain and snow with maybe some sleet and after midnight, sometime in the early morning this should then change over to all snow....

Currently here in Allentown I am sitting at 38 (now at 12 noon) degrees with a dewpoint of 28 and last nights low was 17 degrees....

The areas that will be the warmest will be from Philly point south and east. North and west of those locations will stay colder then what is forecasted in my opinion.....

November 20th Weather Discussion

Early Bite Of Pre Winter Continues!

Today is going to be cold! Well below normal temperatures once again today. Cloudy skies will be the rule with scattered snowshowers anywhere from WV northward into NY State. Some areas may pick up a T to a dusting. Of course this is NOT talking about Lake effect areas or the mountains of WV etc.
Temperatures are going to be on the cold side. For majority of the interior region of NY/PA and NW NJ temperatures will be lucky to climb above the lower 30s. Philadelphia may touch the lower 40s , while southern New England is in the upper 30s. The mountains of WV will not make it out of the 20s. Otherwise to the south of the PA/MD border generally looking at temps in the upper 40s to mid 50s.....

November 17th Weather Discussion

November 17th Weather Discussion

Today is going to be a rather interesting weather day and one that I am not completely 100% accurate on how its going to turn out yet. Lets talk about temperatures first because that seems to be an easier part of the forecast for today.
Along the Southern New England coastline and down into NJ and into Eastern Pa temperatures are going to be in the upper 30s to the lower 40s. This is some 10 degrees below normal. Interior regions of PA should also top out in the lower 40s. These are the Max temps that i expect and they may actually fall short. Further West into Western PA temperatures will be in the low to mid 30s. Interior NY will also only make it into the mid 30s. Below the PA/MD border-upper 40s to mid 50s down in the Norfolk area. Mountains of VA, WVA, mid to upper 20s.

Now the temperatures are out of the way this brings us to the weather for the day into the evening. A S/W is currently located over Indiana. This shortwave should continue to move off to the south and the east. The question is does this energy actually cause greater instability then being forecasted? Does this energy possibly create a weak coastal low off the coast around the Delmarva? This is what I do not have the answer to at this point and time.
Nevertheless the region should experience snowshowers from this clipper. Across eastern PA into NJ by late afternoon, early evening and approaching NYC around or shortly after midnight. I am going to try and update this first thing upon awaking before I have to go to work. There are some questions that still need to be answered in regards to the next 24-48 hours.

October 21-22nd First Snow Possibilities

First snow possibilities....
The area in light blue is basically a zone where I feel that the potential exists for a trace to 1 inch with isolated 2 inches. These amounts though would be in the mountains ONLY.....

Since it would be quite difficult to make a map that shows ONLY mountains accumulations I have decided to use a zone......

PNA/NAO/AO defined and whats needed for a good winter!

A little information needs to be clarified on the PNA and NAO...

A positive PNA will put a ridge on the west coast and a trough along the east coast....
A strongly negative NAO will cause suppression..
A weak negative NAO will be ideal to not cause suppression.....

QUOTE

During a positive PNA pattern, the simulated and observed eastern U.S. jet shifts to the southeast, coinciding with cold, dry conditions in the Northeast. This shift and intensification of the upper-level jet stream during a positive PNA pattern coincides with a greater frequency of cyclones and anticyclones along a distinct southwest-northeast track. Despite increased cyclone activity, total wintertime precipitation is below normal during a positive PNA pattern because of enhanced stability and subsidence over land, along with lower-atmospheric moisture content. Lower surface air temperatures during a positive PNA pattern result in enhanced simulated cloud cover over the Great Lakes and Atlantic Ocean due to increased thermal contrast and fluxes of sensible and latent heat, and a reduction in clouds over land. Interactions between the PNA and North Atlantic Oscillation (NAO) patterns impact the Northeast winter climate. Observed frontal passages through New York are most abundant during a negative PNA and positive NAO pattern, with a zonal upper-level jet positioned over New York. A positive PNA pattern is frequently characterized by an earlier observed Great Lakes ice season, while the greatest lake-effect snowfall occurs during a positive PNA and negative NAO pattern. The NAO pattern has the largest impact on northeast U.S. temperatures and the eastern U.S. upper-level jet during a positive PNA pattern.

PNA/NAO
As you can see it is the NAO pattern which has the largest impact on Northeast US temperatures......
Now lets look at the AO..

QUOTE

The Arctic Oscillation (AO) involves not just the Atlantic but the full band of winds that encircles the North Pole at about 55°N. When this vortex tightens (a positive AO index), it tends to lock Arctic air over the pole. When the vortex loosens (negative AO), frigid air masses can dive more easily into North America, Europe, and Asia. This pattern is also called the Northern Annular Mode, in parallel with its Antarctic counterpart, the Southern Annular Mode.

Pretty simple actually....
A Negative AO means colder air can discharge south
A negative NAO largest impact on the Northeast temps. Necessary for blocking.
A positive PNA Ridge on West coast ..trough in east.
A Negative PNA in Tandem with a Positive NAO means milder and wetter conditions

Some of our biggest storms come with a negative NAO and Positive PNA....
So essentially what you want is a slightly negative NAO or neutral ...a positive PNA or neutral...and a negative AO....

Now look at this chart...

This is showing all Nino, La Nina, and neutral years...from 1948 thru 1993...

Reduced: 75% of original size [ 540 x 466 ] - Click to view full image

As you can see Neutral years are not too shabby for the cities listed here. this is the mean over those years.

Most of the ocean-atmosphere indicators suggest that ENSO-neutral conditions are likely to continue not only during the Sep-Oct-Nov season in progress, but through most of the remainder of 2008 and early 2009.

The chances of an el nino developing are at or about 30%...so thats a 70% chance of not occurring this winter....

So all and all this should show you and tell you what you need for the winter in the Northeast and Mid Atlantic....

I have issued my forecast back in March of 2008 and it will not be altered. Also keep in mind a positive NAO in October correlates to a Negative NAO with historical data for DJF...

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A Colder then normal Winter for the Mid Atlantic? Weak La Nina? Stay tuned to updates.