Archive for October
Cold And Stormy Pattern To Return For New Year
Posted by: | Comments7:27 AM
There are growing indications that 2009 will come in with a bang, at least in the terms of weather. There are signals that are becoming much more stronger for a cold and stormy pattern to develop in the last few days of December and through much of early January. The first key is that the negative EPO pattern will return, which will reestablish the strong ridge of high pressure over Alaska and once again produce a northwesterly upper level flow from northern Canada into the central and eastern United States. The next interesting key, and one that is growing in consensus, is a development of a true negative NAO with a real Greenland block that, if developed as seen on numerous model guidance, will be very difficult to break down. The latest trends in the stratosphere would support the development of blocking over the higher latitudes. However, what has really got my attention is the trends in the Pacific SST data. The support for a strongly negative PDO is pretty much gone, and what has developed and continues to trend to is a weak negative PDO. Why is this important? The weaker the negative PDO is, the weaker the Pacific jet and thus the higher potential for blocking. It is this trend that I was expected back in October, why I disagreed with any idea of a prolonged warm stretch or “blow torch” over the East for January and February. Additionally, the developments of the Pacific strongly support a return of a negative EPO that will be stronger and more sustained.
Now, the pattern I envision for early January is very similar to the one we just had developed, except the cold air will be stronger and the blocking in the Atlantic will be much more favorable. The addition of a true negative NAO in the pattern we are exiting from would have made a huge difference for locations like Philadelphia and southern New Jersey as the cold air would have been locked into the coastal plain. In what seems to be developing for early January, the pattern will be a split flow once again. The northern branch will exhibit a strong ridge in Alaska, slowly trending east through the period towards central Alaska by the end of the first weekend of January with a strong Greenland block, forcing much of the cold air south over southern Canada, the northern Plains, and the Northeast and Mid Atlantic. Meanwhile, the southern branch will have the upper low that was over Alaska now positioned off the Pacific Northwest coast (Seattle may end up having a very snowy period once again out of this pattern) with disturbances traveling over the Rockies into the Plains and moving towards the Mid Atlantic coast. There is growing potential for a storm developing in the southern Plains or Gulf Coast and moving towards the Mid Atlantic coast with a strong, fresh, and sustained cold air mass over the forecast area. So the potential is there, the details unknown, but the one thing that is true is winter is not over.
Cold Conditions On The Way. What About Snow?
Posted by: | CommentsIf you like cold weather, you are going to love this coming weekend! If you don’t, well stay indoors.
The Arctic air mass that we’ve been waiting for since late October will be arriving in the forecast area this weekend with temperatures averaging 10 to 16 degrees below normal for afternoon highs. Friday and Saturday will be very chilly with temperatures struggling in the 30′s even as far south as Cape May, New Jersey. The GFS MOS guidance pushes southern New Jersey into the lower 40′s, but I’m keeping them in the 30′s based on the 850 MB temperature forecasted on the GFS ensembles and ECMWF guidance. Both days will be dry, but rather windy.
So naturally with all this cold air around, the question turns to whether the forecast area will see any snowfall. Well, I’m sure there is plenty excitement with the ECMWF for Sunday into Monday as a clipper low explodes off the New Jersey coast producing snowfall from central New Jersey through New England. The GFS basically has little if any development until the low pressure off the coast intensifies east of New England. The ECMWF currently has little support right now. The reason is simple, the guidance does not pick up any feature that would slow this low pressure system down to cause the intensification seen on the ECMWF for Sunday afternoon.
I’m going with a blend of the model guidance and add in some insight with what we’ve seen in the overall pattern right now. The atmosphere has supported strong redevelopment than forecast by guidance along the Mid Atlantic coast. We’ve seen that repeatably in several storms this Fall and now early Winter seasons. We also must acknowledge that this redeveloping clipper will not be sitting around for too long as the overall pattern is progressive. As such, I think there is a threat for SNOW SHOWERS from roughly central New Jersey on northeastward along the coast including New York City, Long Island, and Connecticut. However, at this time I am not buying into any significant accumulating snow event for Sunday evening. What I would need to see in the next several model runs is some sort of disturbance to slow down the pattern to the north and east of New England to support the type of development seen on the ECMWF.
Regardless, the beat goes on as far as the cold with temperatures remaining well below normal going through Sunday and into Monday with temperatures remaining in the 20′s and 30′s throughout the forecast area.
-- Weather When Posted --
- Temperature: 39°F;
- Humidity: 69%;
- Heat Index: 39°F;
- Wind Chill: 32°F;
- Pressure: 30.08 in.;
December Thoughts
Posted by: | CommentsI know we aren’t done with November yet, but I wanted to build on the winter forecast. Now I know there is a lot of talk going around on the weather boards about the models picking up on a very cold pattern for the eastern two-thirds of the United States going into December. Even the long range models have switched the cold. However, anyone who’s been keeping an eye on the developments of the stratosphere should not be surprised by this development of the model guidance.
To recap what everyone is seeing now. There is strong indication on the GFS Ensembles, GFS, Canadian, and ECWMF Ensembles of a strong -EPO, +PNA, -NAO pattern forming for early December, which will likely lock into a sustained pattern for much of the rest of December.
The models are showing this out come because of what is happening at the stratosphere. It was my hypothesis that the stratosphere will average near to slightly above normal with the potential for some warming episodes. I did not and will not in this discussion forecast when and if major warming episodes will develop, I just don’t have the ability of that skill (yet). However, I can say that the trend continues to support that the stratosphere is near average to slightly above average for November and going towards December. Further, look at the location of the coldest temperatures 
being recorded in the stratosphere. The coldest temperatures at 30 MB all occur over Asia, exactly opposite of last year, btw. What does this tell us?
From research I’ve done and my own hypothesis, this stratospheric set up will support an environment favorable for a ridge over central/eastern Asia, which will lead to a negative EPO trough, which supports a +PNA pattern, and thus a trough over eastern North America. The near normal stratospheric temperatures also lends support for favorable conditions of a negative NAO over time with building heights over Greenland. The GFS ensembles has been showing this development in the long range for weeks, but has been too aggressive and frankly the stratospheric temperatures were just not in position to support a true negative NAO, but rather a north Atlantic ridge. Now we are entering that period of development, just in time for early December. So really, we shouldn’t be surprised by what the models are showing here.
My thoughts for December is the following. The cold source over northern Canada is building with high temperatures in the -30′s F, so there is no doubt that cold air has been developing thanks to the strongly positive AO in October and the latter half of November. The pattern will begin to develop next week with the developments in the Pacific leading to an amplification of the northern branch of the Polar Jet Stream. I think the cold air will first impact the Plains and then the rest of the east for the first week of December. I wouldn’t be surprised if the forecast area returns to near to slightly above normal for the first few days of December. 
Then the bottom drops out for the next three weeks of December. The pattern locks in, the cold arctic air remains on this side of the hemisphere, which will produce below normal temperatures over the forecast area.
As far as the potential for storms. I don’t buy the intensity of the NAO in the long range. For the past several weeks we’ve seen long range guidance produce too strong of a NAO on either side of the scale. This aspect of the forecast will be key in determining if the forecast area will have a cold/dry December or a cold/stormy December. History tells us that a weak negative NAO is the best environment for winter storms for the forecast area. The weak negative NAO does not suppress the storm track, but keeps cold air locked in over the coastal plain due to a strong high pressure system over southeastern Canada. The strong negative NAO though suppresses the pattern, which snow lovers likely would not enjoy unless you are in the Great Lakes. So the state of the NAO, once again, will be a key driver in the type of cold pattern we will see. However, have no doubt, December will be cold.
-- Weather When Posted --
- Temperature: 30°F;
- Humidity: 54%;
- Heat Index: 30°F;
- Wind Chill: 30°F;
- Pressure: 29.88 in.;
Evening Thoughts
Posted by: | CommentsThere’s a lot of topics I want to cover tonight so lets dive into it!
First and foremost, the heaviest rainfall from this afternoon’s coastal low is now off the coast and I only expect a few light showers and some drizzle for the rest of the overnight period. There is plenty of deep moisture still left over the forecast area that is streaming out of the Gulf of Mexico. As winds begin to veer to the south and southwest from the surface to 500 MB by the morning, a warm and humid air mass will build into the forecast area. Weather conditions will resemble spring like conditions through much of the day on Friday. Given that humidity will fall below 50% at 700 MB, I think there will be some breaks in the cloud cover, however plenty of low clouds in the morning will lead to a mostly cloudy day through tomorrow afternoon.
Meanwhile, a strong disturbance will amplify the 500 MB trough on Friday evening as a new area of low pressure develops over the Tennessee Valley and tracks towards central New York by Saturday morning. A strong cold front will follow with a developing thermal gradient of 8 to 12 degrees from the East coast to the Ohio Valley. The dynamics setting up over the forecast area will support embedded elevated thunderstorms over the forecast area on Saturday. Don’t be surprised if some of the thunderstorms briefly reach severe levels, especially with strong down burst wind gusts. Rain cooled air will rush down to the surface in these thunderstorms and produce strong wind gusts, possibly to 50 mph in isolated locations. The cold front will clear the forecast area by Saturday evening with temperatures crashing through the 40′s.
So now the cold front has passed and the pattern has evolved, what will the new trough hold for the forecast area? The answer is winter like conditions. First, expect temperatures to be on average 8 to 12 degrees below normal through much of next week. Second, a series of small yet potent disturbances from the northern branch will race through the forecast area. Overall, these disturbances will not have the potential to produce wide spread, heavy precipitation. However, given the strong lifting of these disturbances and the 850 MB temperatures remaining well below zero throughout the forecast area; the forecast area will have the potential for snow showers Tuesday through Thursday. I think the best potential for this in the evening hours and likely over the northern Pennsylvania, northern New Jersey, the Hudson Valley, and Connecticut.
Now, lets get to the topic that is raging on all the weather boards out there! Is the ECMWF really forecasting a returned Southeast ridge and a blow torch pattern for the end of November. Remember what I said way back in October, do not trust nor jump on one model run or even a few model runs in the long range. Remember, the models in the long range are dealing with an atmosphere with very weak signals, and you can bet the GFS, ECMWF, and ensemble guidance will continue to forecast a variety of solutions. This is why those who hug models are going to get serious burned this winter, in my opinion. I can promise all of you that from run to run, no matter the model, that the hours of 192, 210, and 240 will show everything from blow torches to monster blizzards from run to run this winter.
As I explained this morning, I think the pattern will relax during the beginning of the last week of November. The northern jet stream can not stay amplified forever, and thus a relaxation in this period is reasonable. However, the stratosphere does not support a warm pattern in the East in my opinion. The stratospheric temperatures at 30 MB are generally running near to slightly above normal, which will continue to support a neutral to negative AO and NAO. This is the current OBSERVATIONS and not some model solution. Taken this fact, I think the idea of a neutral or positive NAO for the last week of November and the first week of December is not reasonable. This is likely a hiccup for the ECMWF and not a trend for the long range, in my opinion.
In fact, several GFS ensemble guidance strongly supports a negative NAO and a cold pattern in the East and I think this guidance is correct due to the observations at the stratosphere. I would not be surprised if the ECMWF flips back cold this or the next model run.
Anyone who is going to be basing the winter on run to run of models will like lose their hair, money, and/or sanity. I would strongly suggest those individuals to not to do this.
Have a great night!
-- Weather When Posted --
- Temperature: 57°F;
- Humidity: 93%;
- Heat Index: 57°F;
- Wind Chill: 55°F;
- Pressure: 29.99 in.;
Change Is In The Air
Posted by: | CommentsNo, I’m not talking about politics. Please! I’ve had enough.
The pattern is about to go through a significant and lasting change that I think will begin to lock in for much of the winter. I am going to go back to what was discussed in my winter forecast and start where I think everything will begin. The stratosphere.
The signs are beginning to show that the stratosphere will not repeat the very cold set up that was seen last year as trends continue to support a near normal environment for stratospheric temperatures. I have also seen an interesting trend in the stratospheric data at 30 MB, that when slightly cooler than normal values are seen in October, like this year, that there is a higher potential for significant stratospheric warming in December, January, and February. The correlation of these events are not the most impressive, but there does seem to be a trend. So I think the potential is certainly there. What it is important to note at the stratosphere right now, is that there is support for a more favorable atmosphere at the troposphere to allow for blocking over the northern latitudes. Namely the development of the negative AO and negative NAO.
Meanwhile, the Arctic Oscillation is officially at a neutral state! The AO continues to drop and will enter the negative range for the first time since early October. After what was a period of a strongly positive AO, all indications continue to support the development of a strong negative AO. Now, guidance has backed off to tanking the AO to a negative 4 standard deviation, at least for now. Instead, the ensemble guidance takes on a more reasonable step down approach with some wavering towards neutral from time to time. However, with each rise towards positive, the guidance appears to drive the AO deeper towards the negative state. In fact, by the end of November, almost all ensemble and operational GFS guidance takes the AO state deeply into a -1 to -2 standard deviation. This state of the AO would strongly support colder conditions over the forecast area and a general trough in the East.
The NAO current state is slightly positive, just around 0.5 standard deviation above normal. The guidance takes the NAO into a slightly negative state going forward through November and towards December. This is very important. Despite what some believe, snow lovers do NOT want a strongly negative NAO. Most coastal storms and storms of that produce significant snowfalls occur in periods where the NAO is in a state of change are not strongly positive or negative. A strongly positive NAO means that no blocking exists to hold high pressure systems over New England and generally allows the strong track to move into the Ohio Valley. Meanwhile, a strongly negative NAO suppresses the storm track and forces most disturbances well to the south and east. This index is kind of like the pourage from the old fable. Not too cold and not too hot, is best for the NAO to rock.
So as we move forward into November, enjoy the warm weather for Friday and Saturday morning, because the rest of the month overall looks to be colder than normal and much stormier. In fact, by next week another coastal low will develop to bring some frozen precipitation to the forecast area. However, that story is the next post!
-- Weather When Posted --
- Temperature: 57°F;
- Humidity: 87%;
- Heat Index: 57°F;
- Wind Chill: 54°F;
- Pressure: 29.96 in.;
Drought Page Updated
Posted by: | CommentsThe drought data for October over southern New Jersey has been updated along with a discussion on the current events.
Frankly, I don’t see much improvement in the situation going forward.
-- Weather When Posted --
- Temperature: 57°F;
- Humidity: 58%;
- Heat Index: 57°F;
- Wind Chill: 57°F;
- Pressure: 30.25 in.;
A Quiet Period Of Weather Expected
Posted by: | CommentsOverall, the last day of October through the first week of November will generally be rather quiet.
High pressure will slide to the south and east of the forecast area today, however clear skies will continue through the day. A cold front, the only significant low pressure system over the next several days, will move through the forecast area tomorrow morning. The main influence from the cold front will be a drop in temperatures and a brief reenforcing shot of Polar air for the forecast area.
Strong high pressure will remain in control Monday through Thursday with clear skies. A strong ridge at 500 MB will reach a peak on Tuesday before slowly giving way to an Ocean storm in the Atlantic and an approaching trough moving from the Plains to the East coast. Temperatures through next week will run at or above normal for many locations with temperatures in the 50′s and 60′s for highs.
The potential remains for a significant coastal storm to impact the forecast area for next week.
-- Weather When Posted --
- Temperature: 33°F;
- Humidity: 80%;
- Heat Index: 33°F;
- Wind Chill: 27°F;
- Pressure: 30.49 in.;
A Quiet Start To November
Posted by: | CommentsAfter all the active weather to end October, looks like November will be starting in just the opposite. A strong ridge will dominate the weather pattern at 500 MB through next week, which will support high pressure over the forecast area through the first week of November.
While a strong surface low and deep trough slowly moves east over the Rockies and the East, the ridge will provide the region with temperatures averaging near to slightly above normal with 850 MB temperatures ranging from 6 to 8 degrees C. Now I did stay on the cool side for the interior due to some of the impressive snowfall on the ground already, but gave less weight to this factor towards the end of the forecast period.
Meanwhile, under the ridge, trouble appears to be brewing in the Atlantic, which will have to be watched next weekend.
-- Weather When Posted --
- Temperature: 33°F;
- Humidity: 64%;
- Heat Index: 33°F;
- Wind Chill: 26°F;
- Pressure: 30.22 in.;
A Surprise Snowfall For The Forecast Area
Posted by: | CommentsThis morning I suggested that the rain will gradually change over to snow over most locations, but accumulations would remain the interior sections of northeastern Pennsylvania, northwestern New Jersey, and the Hudson Valley.
You can imagine my surprise when I observed the rain changing to snow and accumulating in central New Jersey, specifically Freehold. Now, the snowfall accumulations were mainly on the grassy surfaces, however the fact that snow accumulated this early in the year was impressive. So we have the first snowfall in Freehold, New Jersey on October 28th!
Before I go over what caused the snowfall, I just want to highlight some of the impressive totals over the forecast area:
HIGH POINT STATE 14.0 400 PM 10/28 Sussex County New Jersey
TOBYHANNA 16.0 700 PM 10/28 POWER OUTAGES Monroe County, PennsylvaniaLEBANON 12.0 500 PM 10/28 950 FT Hunterdon County, New Jersey
So what caused these impressive snowfall amounts? The answer can be found at 500 MB! This morning, the significantly amplified trough that was driving towards the coast closed into a rapidly deepening 500 MB low directly over the forecast area. As the heights crashed due to the rapidly intensifying upper low, much colder air aloft dropped towards the surface, which allowed for the change over from rain to snow even down towards the coast line. Meanwhile, the strong mid and low level forcing due to the developing 500 MB to 850 MB lows enhanced the precipitation over the forecast area. The heaviest snowfall fell over the higher elevations due to a combination of colder temperatures, which allowed for faster accumulation, and because some of these locations were under a very strong area of forcing, which enhanced the precipitation.
The surface low pressure will continue to move rapidly towards southeastern Canada and produce very windy conditions through tomorrow. Weak disturbances will rotate through the forecast area around the strong upper low, which will support the threat for rain/snow showers through tomorrow afternoon.
-- Weather When Posted --
- Temperature: 41°F;
- Humidity: 75%;
- Heat Index: 41°F;
- Wind Chill: 33°F;
- Pressure: 29.55 in.;
Long Range Thoughts
Posted by: | CommentsI want to continue the winter discussion from the overall forecast that I made with actually following up on the forecast. The main issue we need to keep an eye on is the stratosphere, as any indication of a significant drop of temperatures over North America will basically kill any potential for a negative AO and NAO for this winter, which I think will be a bigger issue for the forecast area than the PDO index overall.
As of the latest data, there is still no indication of a significant drop in temperatures with the average stratospheric temperature remaining near normal and the minimum temperature remaining above normal. However, it is not just a question of the magnitude of the temperature anomalies, but also where those anomalies are occurring that is key.
Seen here to the left, it is clear that the coldest temperatures are located on the Asian side of the northern hemisphere as of last night. We have seen this trend throughout the fall with little change in the position of stratospheric structure. This is a significant observation for the winter outlook because this supports a more favorable environment for a negative AO and negative NAO for North America, rather than what we saw last year, which was a strong positive AO and NAO due to the coldest air over North America at the stratosphere. So remember, it’s not just magnitude but location as well.
Now naturally, the influence of the stratosphere leads us to the next question, what can be expect from the AO and conversely the NAO in the next few weeks?
As we have all seen, the AO has been STRONGLY positive the past few weeks and basically through much of October. However, there are indications that the AO is about to crash.
In the following charts we will see the current and forecasted trends of the AO, NAO, and EPO indices, which are all important to determine the type of winter we can expect. Remember, it was my theory that when the AO goes negative, we will see an EPO and NAO trend towards the negative as well. Note though that while the AO can stay in a stay for a longer period of time, the EPO and NAO have shorter phases and can waver. The point here is that we are moving towards a trend once again of an AO about to take a serious fall and the EPO and NAO supporting a more pronounced trough over eastern North America for the middle and end of November and most likely into early December.
-- Weather When Posted --
- Temperature: 51°F;
- Humidity: 53%;
- Heat Index: 51°F;
- Wind Chill: 46°F;
- Pressure: 29.8 in.;
Freehold
57°
Philadelphia
62°
Albany
59°
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