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

25 11 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…

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A pre-Thanksgiving Snowstorm Looking More and More Likely!

24 11 2014

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!

15 11 2014

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

2 03 2014

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.





Our Astonishing Winter Continues; Preliminary Preview of the Early March Snowstorm of 2014

28 02 2014

Hey everyone.

“There can’t be! There’s no way. There won’t be!” Those are only some of the phrases I have heard this week after telling people about the upcoming major storm on its way.  Today, I will cover some of the general details of this storm. Tomorrow’s post will cover more of the details including timing and my snow-map.

A low pressure system that is currently drenching California with much-needed rain (severe storms in LA) will move across the country and gather a substantial amount of moisture tomorrow and Sunday. The storm will become elongated as it partially phases with another piece of energy before this snake of precipitation moves through the region. The timeframe for this storm will be from Late Sunday night to early Tuesday morning.

GFS model 1 PM Monday

GFS model 1 PM Monday

This will be a very long and drawn out storm. A round of heavy precipitation will start on early Monday morning and won’t end until the nearly the same time the next day. While there has been some model inconsistencies regarding the exact path of this storm, there looks to be enough cold air in the upper atmosphere to support snow for most of the storm. South Jersey and Philadelphia could mix a little bit during the storm it it comes further north, but this shouldn’t be enough to alter snow totals significantly.

More details will be discussed in tomorrow’s post.  Overall, this will likely be very significant storm with totals exceeding 6 inches in most places in the Delaware Valley. Welcome to March. 

Until then…..





Final Forecast and Snow-Map for Mid-February Snowstorm of 2014

12 02 2014

A very large nor’easter (surprisingly, our first nor’easter of the winter) will affect the Northeastern United States late tonight into tomorrow. Even though the forecast models are still not completely in consensus about the location of the rain/snow line, I am confident enough to make an official forecast for this upcoming system.

Part 1: The Forecast

My forecast is based on a combination of the European and NAM model solutions. The NAM tends to really amplify the precipitation tomorrow morning, while the European has a more realistic precipitation field. The problem that many forecasters are faced with right now is whether a changeover to mix/rain will occur sometime tomorrow. While I believe that sleet could fall for a time around Philadelphia and its immediate suburbs tomorrow, I do not think it will last long. If the snow continues to fall heavily tomorrow morning, dynamic cooling will occur and keep the precipitation type all snow. If a lull in intensity occurs, a changeover could occur as warm air from the ocean comes in aloft. Either scenario, I believe that this will be a significant snowstorm with drastic effects on people’s lives tomorrow and Friday.

Part 2: The Map

My snow-map below shows the most snow falling north of the immediate Philadelphia area and into Northern NJ and Maryland. It is in these areas where the precipitation will likely stay as all snow and be very intense for most of the morning tomorrow. I am calling a general 11-15 inches for this area. For people living along I-95, a general 7-11 inches is expected with the snow changing to sleet, then back to snow by tomorrow midday. In south jersey and along the coast, totals will really be held down by mixing and rain.

Forecast for Mid-February Storm of 2014

Forecast for Mid-February Storm of 2014

Part 3: Timing and Intensity

This storm will not be a short one. A full 24 hours of precipitation will fall from early Thursday morning to early Friday morning.

1 AM Thursday-4 AM: Light snow starts from South to North

4 AM- 2PM: Peak of snow, could change to sleet in southern part of the region

2 PM-5 PM: Possible lull in precipitation (changeover likely to sleet over I-95)

5 PM-11 PM: 2nd round of moderate snow for most of the region

11 PM-3 AM: Friday: Ending South to North

Morning and evening rush hour on Thursday will be treacherous. Morning rush hour on Friday will also be extremely slick. The winds will also be high during this storm, which means for possible power outages during the height of the storm on Thursday. If you really have to drive tomorrow or Friday morning, make sure to take it slow. Schools will be closed on Thursday and possibly Friday depending on final totals.

Luckily, we are looking at a substantial warmup next week with temperatures possibly getting into the 50s, which will help us with melting some of this snow!

Enjoy the storm!





A Preliminary Review and Uncertainty of the Upcoming Snowstorm

11 02 2014

The active weather pattern of February 2014 continues. A large nor’easter will affect most of the East coast from Wednesday night until late Thursday night, bringing strong winds and heavy precipitation to the Eastern seaboard. The question that remains is whether the precipitation will stay as all snow, or mix during the storm.

Part 1: Difficulty of the forecast

Forecasting this storm for the Philadelphia region has been far from easy. The amount of cold air in the upper atmosphere is unremarkable, which means that the rain/snow line will be very close to the city, with areas in south Jersey likely turning to rain sometime during the day on Thursday. The storm track will be key as it runs up the coast and strengthens.

If the storm is closer to the coast,  more ocean influenced warm air will be present aloft and mixing issues will occur for areas close to the city. A storm closer to the coast also means more precipitation, which could offset the mixing issues that we would have from the storm. If the storm is further from the coast, more cold air will be present aloft, but precipitation values will be lower than they would be if the storm retrograded near the coast. Conclusively, it seems like each path has its pros and cons concerning precipitation type and amount. In the image below, the blue dotted line shows the projected rain/snow line. Note this is only a projected value.

NAM Storm Location

NAM Storm Location

Lastly, many models have trouble projecting exact upper air patterns when a storm of this magnitude runs up the coast. Many times, storms this strong produce their own cold air, and many places expecting mixing issues stay below freezing.

Part 2: My Preliminary Forecast and Timing

My belief at this point is that this storm will be strong enough to keep areas around the Philadelphia region and just south all snow, which would maximize snow totals. I do believe that south Jersey and any areas close to the ocean will mix at some point during the storm. This will hold down totals in these areas. 

There is a catch, however. Many models have been showing a more westerly track recently, and I still am not ready to release a snow map to the public. Even 24 hours before the storm, there is still lots of uncertainty on the track and how much mixing will occur along I-95.

GFS Track more West

GFS Track more West

 

What is certain is the timing of this storm. The snow should start early Thursday morning and peak during the morning on Thursday. Things should start to slow down by Thursday evening, with precipitation ending by 10 PM on Thursday for most areas.

The effects of this storm will be great with or without mixing. Most schools will be closed on Thursday. Roads will be dangerous and I recommend to stay home regardless of the precipitation type.

I will be updating tomorrow with an official snowmap and my final forecast. Stay Tuned.

 








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