48 Hours of Snow Coming! Forecasting the Nor’easter on Tuesday


It is going to be an extremely eventful next 72 hours for the region and the northeast as a whole.

As a mentioned in my last post, a small clipper system will pass through the area late tonight and tomorrow. This storm has the stereotypical features of a clipper: plenty of cold air, fluffy snow, a general 2-4 inches for most. Precipitation will start falling late tonight and continue throughout the day tomorrow.

NAM Model Monday
NAM Model Monday

At this point, the situation gets complicated. After the clipper exits the coast, it will interact with a weak disturbance off the Atlantic coast and strengthen rapidly into a nor’easter. Plenty of moisture will be fed into the storm from the ocean, and plenty of cold air will be present as well. The question that remains is where and when this storm will strengthen. Models have been a little inconsistent with the timing of the phase and where it will occur. The further west the storm phases, the more snow we will receive in the Philadelphia area. In New York City and Boston, blizzard conditions will be likely.

Model Analysis:

European: The European has been the aggressive model for this storm. Most of the solutions it shows bring the storm close to the coast and drop 10-15 inches of snow with totals higher in New Jersey and areas closer to New York.

European Model
European Model

GFS: The GFS model has been the more conservative model, showing a slower phase further east than the European. It’s latest runs have been having convective feedback issues, however, which means it’s solution may not be accurate. Until these issues are resolved, I will not be favoring this model when making my forecast.

NAM: The North American Model is the middle ground between the two previous ones. It is projecting 8-12 inches falling by Wednesday morning. I am favoring this model the most out of the three because of its increased accuracy in the short run.

NAM Model
NAM Model

Timing :

12 AM-6 AM Monday: Snow will start west to east

6 AM- 6 PM Monday: Snow accumulating a general 2-4 inches during the day

6 PM Monday- 2 AM Tuesday: Light Snow as storm strengthens off of coast

2 AM – 5 PM Tuesday: Snow. Heavy at times. Accumulating 5-8 inches (or more depending on location of storm off coast)

5 PM Tuesday – 3 AM Wednesday: More snow, eventually tapering off late night on Tuesday

The official Forecast:

While the clipper forecast is fairly straight forward, the following nor’easter involves many dynamic components which need to be ideal for a major snowstorm to occur in the Delaware Valley. Even though these conditions are favorable, there is still some uncertainty in the exact amount of snow we will receive by Wednesday morning. Temperatures will be in mid-20s, which means a light fluffy snow will fall. These low temperatures also increase the snow to precipitation ratio, which means snow will accumulate faster than normal.

The snow map below shows totals from the clipper and the nor’easter combined. Depending on the formation of the low off the coast, the 10-14″ area is subject to shift in the next day or two. Overall, 6-10″ inches is good bet for the city and areas south and west. Totals will be higher closer to NYC and even higher near Boston, where blizzard conditions will likely occur.

Snow Map for the One Two Punch
Snow Map for the One Two Punch

Effects on travel will be significant on Monday and Tuesday. Businesses and schools will be shutdown on Tuesday, and I wouldn’t count out some cancellations on Monday as well. Stay off the roads and be safe. More

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Messy Saturday Coming. Snowy Monday as Well?


Hey everyone. Quick post here.

We are looking at a very messy and slushy overnight and Saturday as a large storm system will ride the coast in the next 12-24 hours. While I was wrong with my initial thoughts of a plowable snow event, I was correct when I said there is just not enough cold air aloft to produce snow.

NAM Saturday Morning
NAM Saturday Morning

The precipitation will start in the next few hours and continue throughout the day tomorrow. Snow totals will likely be around 2-4 inches north of Philadelphia and 1-2 inches to the south. Precipitation will initially start as snow then switch over to rain sometime tomorrow morning before changing back to snow by tomorrow afternoon. The storm should be over by tomorrow night.

NAM Saturday Evening
NAM Saturday Evening

I am also tracking a clipper system which will ride through the area on Monday. Many of the models are keeping the storm suppressed to the south at this point, which would mean lower totals for the region. Regardless of the amount of snow, travel conditions on Monday will not be ideal. I would not rule out school cancellations and numerous travel delays. I will go more into detail for this storm in the coming day or two.

Euro Monday Morning
Euro Monday Morning

Other than that, drive slow tomorrow and enjoy the slushy mess!

Taking a Closer Look at the Upcoming Winter Storm on Saturday


Hey everyone. It has been quite a while since my last post. Winter 2014-2015 has been fairly quiet and cold so far. According to reports, we have only received 1-2 inches of snow so far this winter. This is much lower than what we had at this time last year.

Temperatures this winter have been around average so far. December finished 4 degrees above normal, while January has been nearly 3 degrees below normal. This contradicts my original forecast, where I said January would be warmer than December. An explanation for this flip in temperatures lies in the El Niño strength over the past couple months. The Niño we’re currently experiencing decreased from December into January, this indicates why our temperatures have been colder in January compared.

Current El Nino
Current El Nino

In current news, I am currently tracking a winter storm during the day on Saturday. Analytical indicators have been favoring a large storm streaming up from the Gulf of Mexico and intensifying off of the Mid-Atlantic coast. While the setup for this storm is not perfect, I do believe a plowable amount of snow will fall north and west of Philadelphia.

The Setup

Current models have been showing less than ideal conditions for a major east coast snowstorm. The most major flaw in the pattern right now is the lack of a “Quebec high”, which tends to bring frigid Canadian air down and feed the cold side of the storm. There is also no indication of strong blocking ahead of the storm, which means that there is a chance that it could quickly run east of the benchmark. This ultimately means that we could have some mixing with this storm as well as a sharp cutoff in the amount of precipitation north and west of the city.

Let’s look at some of the models:

The European and North American Model (NAM) have been aggressive with the amount of moisture associated with the storm. They also forecast the storm further west than some of the other models. With both models, however, mixing will be an issue south and east of the city. While snow totals could be around 6-8 inches for Philadelphia north, in South Jersey snow totals may be limited to 2-3 inches at the most. This mixing issue, as I alluded to earlier, is from the lack of the Canadian high providing cold air for the strengthening storm.

European Major Snowstorm
European Major Snowstorm

The GFS model has been possibly underestimating the strength of the storm. As a result, it brings the track further out to sea, which diminishes snow totals throughout the region. A general 2-4 inches would be expected if the GFS solution was the correct one.

GFS Model
GFS Model

At this point, I am leaning toward the Euro and NAM solutions. The reason for this lies in the Arctic Oscillation teleconnection, which is one of the main indicators I use to determine the strength of a storm. As you can see from the graph below, the AO is projected to sharply become positive a day after our storm pulls through. Any time this happens, it tends to indicate a change in the upper atmosphere in the arctic circle, possibly caused by a major storm system. This metric has increased my confidence for a larger and stronger storm on Saturday.

Arctic Oscillation
Arctic Oscillation

I will have more updates as we get closer to Saturday. I will release my snow map Friday night.

Thanks everyone!

Final Forecast and Snow Map for The Pre-Thanksgiving Storm of 2014


After a quick warmup on Monday, winter is back with a vengeance tomorrow with our first snowstorm of the season. There have been a few changes since I posted yesterday Morning.

Firstly, surface temperatures will be hovering at or a little above freezing for most of the day tomorrow. This, combined with warm upper air temperatures, will cause the snow to mix with rain initially before changing to snow later in the day. Areas further north should expect an earlier changeover, while most of South Jersey may not see a complete changeover to snow during the storm.

2m temperatures Wed afternoon
2m temperatures Wed afternoon

Since it is still November, forecasting snow totals for this storm is extremely difficult.  The most recent short-run models have been favoring a more west track. This means less snow for the region than originally expected. My snow map shows 2-4 inches falling in the city with 3-5 inches in the immediate northern and western suburbs. If the storm takes a more westerly track like the short-run models are showing, these totals could fall substantially.

This map below shows an example of how a small shift in the track could affect snow totals. A 10 mile shift west or east in the storm track is the difference between 8 inches of snow and none at all in Philadelphia.

RGEM model snow projection
RGEM model snow projection

Timeframe:

  • 4-6 AM Wednesday: Light Rain Enters from South to North.
  • 6-10 AM: Rain becomes heavier and turns to snow Philadelphia northward.
  • 10 AM-5PM: Becoming all snow from northwest to southeast. Heavy at times. Possible thundersnow in spots.
  • 5 PM-8 PM: Snow becoming lighter
  • 8PM-11 PM: Snow moves out from south to north

Finally, I will release my first snow map of the season. This map is based on a combination of multiple computer models I have analyzed over the past few days. If you have any questions or concerns regarding the map, please let me know in the comments.

Snow Map 11/26
Snow Map 11/26

Be safe everyone. Remember that this snow will be of the wet and heavy variety, which means sporadic power outages and downed trees around the region. Until next time…

A pre-Thanksgiving Snowstorm Looking More and More Likely!


Hey everyone.  What makes predicting the weather so interesting is the unpredictability of it.

This is what has happened with the latest forecast models projecting possible Thanksgiving snowstorm. Yep. Nor’ Easters in November.

Lets get to it!

1. Tomorrow will likely reach into the 70s with some rain ahead of a strong cold front which will pass through on Monday night. I wouldn’t be surprised if the sun peaked out sometime in the afternoon. After the front moves through, temperatures will plunge throughout the day on Tuesday. This is shown below, courtesy of the GFS:

GFS Monday at 2 PM
GFS Monday at 2 PM

2. After the front moves through, a blocking high will move into Atlantic Canada, forming the setup for a storm to form along the coast. Another small disturbance will also move in from the midwest, phasing with the budding coastal system. This will really begin the process of a large storm forming on early Wednesday morning.

GFS 5 AM Wednesday
GFS 5 AM Wednesday

So the setup is there for a large snowstorm, but will it happen?

At this point, most forecast models are showing some sort of storm riding up the coast Wednesday into Thanksgiving. Since we are in November, the problem lies in whether there will be mixing during the storm. Upper air temperatures could be above freezing during the storm, especially if it runs close to the coast. This would bring in some wintry mix to the region at the beginning of the storm before changing to all snow.

On the other side, some models are showing dynamic cooling at the surface, which could keep the precipitation type all snow for the duration of the event.

Model differences:

GFS:

The GFS is showing a solution which would go further to the east. This solution I am supporting right now.  In the end, the GFS projects a good 3-6 inches of heavy snow falling from DC to Boston. This will be enough snow to disrupt travel plans and create mass power outages (which is not good if you want to watch the Eagles game, like me). The maps below show the peak of the storm on Wednesday at 2 PM. Click the maps to see a larger version.

GFS 2 PM Wednesday
GFS 2 PM Wednesday

European:

The European model is projecting the storm to come further west near the coast. Since the storm is closer to the coast, temperatures at the surface will have trouble staying below or at 32 degrees. The upper air temperature will be above freezing as well, which could mean a mix of precipitation throughout the storm. Even though the Euro projects more total precipitation than the GFS, 3-6 inches would be a good estimate for final snow totals from this model. Below is the European model at 8 PM Wednesday night. Obviously it is a slower solution than the GFS, which means there is more time for the storm to strengthen.

European 8 PM Wed
European 8 PM Wed

So which solution is correct? Well the European ensembles show a solution more toward the GFS. The teleconnections are also marginal for a large nor’easter storm that retrogrades into the coast. As a result, my initial call is 3-6 inches for the I-95 corridor with totals lower by the coast and higher up in the Lehigh Valley. The timeframe is from Wednesday midday to Thursday early morning.

I will have more on the travel effects and my snow map either tomorrow night or Tuesday morning.

Stay tuned everyone! Let the winter of 2014-2015 begin!

Welcome Back: My Winter Forecast and a Cold November!


Hey everyone. After a spring/summer hiatus, Philaburbia Weather is back for the 2014-2015 winter season!

I want to start this post off by thanking everyone for staying with Philaburbia through the years. We are heading into our 5th winter and I hope you are as excited as I am for the coming months ahead!

First on the agenda is the tropical outlook. The 2014 hurricane season in the Atlantic is about to officially end. With only 9 named storms, it has been a fairly unremarkable season in the tropics. A couple factors including cooler than normal ocean temperatures and a weak El Niño contributed to the lessened activity in the Atlantic.

Atlantic Temp Anomalies
Atlantic Temp Anomalies

My mention of the El Niño leads us into the next topic: What’s in store for the 2014-2015 winter season?

A couple of major factors will determine how cold and snowy our winter will be:

1. Strength of the El Niño: This parameter has been known to heavily influence our winters year in and year out. In a nutshell, an El Niño means that water temperatures off the coast of Peru are above normal. No one knows the exact reasons for El Niño’s effects on our winter weather, but research has been done to prove correlations between strength of the El Niño and meteorological averages in the continental United States.

El Nino
El Nino

 

We are currently headed into a weak El Niño from a weak La Niña last winter (see chart above). With El Niño winters, temperatures tend to be warmer than average in the Northeastern United States. Unfortunately, the magnitude of the El Niño this winter will be marginal at best, which makes it difficult to predict how warm this winter will be. I did, however, find a couple of analog winters. These could support a general trend for this winter.

Analog winter: 1990-1991. The first winter I chose to analyze was the winter of 1990-1991. This winter was one of the warmest on record for the Eastern United States. The El Niño recorded during this period was weak (see http://ggweather.com/enso/oni.htm for more), but was likely largely influential on the unusual warmth of this particular winter.

1990-1991 winter analog
1990-1991 winter analog

Analog Winter: 2002-2003: This winter was made famous from the Presidents Day Blizzard of 2003, where nearly 20 inches of snow fell in Philadelphia. Overall, the winter of 2002-2003 was remembered as being one of more snowy winters in recorded history. The El Niño during this winter was weakly moderate, and temperatures were actually below normal for the season!

Presidents Day Storm of 2003
Presidents Day Storm of 2003

These two analog winters had very different kinds of winters. This does not make it easy finding correlation and a pattern to base my forecast on. Luckily, other factors, like teleconnections, are important indicators during the winter that help forecasters fine-tune their predictions.

2. Teleconnection Strength: Multiple teleconnections, including the AO, NAO, and the PNA, will be crucial in determining the winter pattern. The Arctic Oscillation (AO), is an index which records the pressure anomaly in the arctic region. A positive AO usually means a warmer winter, while a negative AO usually signifies a colder one. Currently, the AO will stay negative over the next few weeks, which means the rest of November will be much colder than average.

The North American Oscillation teleconnection is an important indicator of the intensity of winter storms in the Northeast. Last year, we had a positive NAO, which limited the number of nor’ easters to just one. If the NAO turns negative this winter, there is a strong chance we will have a couple very large snowstorms, ones that will drop feet of snow.

The Philaburbia Weather Winter Forecast of 2014-2015:

After last year’s extremely cold and snowy winter, we will not get too much relief this year. Already, we are seeing temperatures way below normal for November and an AO that looks to be staying negative for the near future.

However, there are some indicators that the end of the winter could be warmer than last year’s. With a weak El Niño developing, there is a possibility that the Polar Vortex will retreat back north, which would cause our February and March to be much warmer.

In terms of snow, I think we are in for less frequent smaller storms and more large nor’easters than last year. I could easily see most of the snow falling this winter from 2 or 3 large nor’easters and nothing else. As a result, our area could see 30-40 inches of snow this year depending on how many nor’easters hit and how intense they end up being.

To recap:

1. Cold winter. February and March becoming warmer than average. Temperatures 2-3 below average in Dec and Jan. Temperatures 2-3 above average in Feb and March.

2. Snowy winter. Less smaller storms, more larger ones than last year. 30-40 inches of snow.

Thanks everyone! Stay tuned.

 

Final Forecast for Early March Snowstorm; Less Snow than Originally Predicted


Hi everyone.

Since the last time I posted, many of the models have been suppressing the storm to the south. While we are still looking at a significant snowstorm that will bring plowable snows to the region, totals will be less than I originally predicted. The map below shows the RAP model projecting snow falling at 5 AM tomorrow. The precipitation field will be moving in a southeast direction with this storm.

RAP model 5 AM Monday
RAP model 5 AM Monday

Because the storm will be suppressed to the south, this means that the length of the storm will be greatly reduced. Snow will start late tonight and likely end by early afternoon tomorrow. Instead of a 36 hour storm we were looking at a day or two ago, we are looking at more of a 12-18 hour one. Totals will still be substantial in the southern and eastern parts of the region with south Jersey and Delaware possible receiving a foot of snow. Northern suburbs will receive around 3-6 inches and Philadelphia will likely have 6-8 inches of snow on the ground by tomorrow afternoon. Confidence is high on these storm totals and storm path, as much of the upper air factors are already in place and will  not likely change.

Snow Map for Early March Snowstorm
Snow Map for Early March Snowstorm

The effects of this storm on morning rush will be significant, as heavy snow will be falling through 10 or 11 AM. My guess is that many schools will have delays or close tomorrow as the bulk of the snow will fall in the morning.

I will continue to monitor the progress of this storm during the day today and will provide any updates if there are changes in track or timing.