We’re going to look at the same four models as we did for Hurricanes Henri and Ida last summer. However, I just launched a complete redesign of this blog less than a week ago. That redesign will allow us to analyze the models in a way that’s much easier to compare, and hopefully much easier to understand. Let’s get started.

Big Picture Overview

When I look at the “big picture” meteorological setup, I immediately see just how similar this setup is to the October, 2021 nor’easter. That storm slammed into southern New England on 26 October, packing wind gusts over 100 mph (160 km/h) and heavy rains. Trees and power lines were down all over the place, knocking out power for several days. At one point all of Massachusetts south and east of the I-95 corridor was 100% without power.

Likewise, the current storm is a rapidly strengthening, or “bombing” cyclone. To be classified as a bomb cyclone, a storm must undergo a 24 millibar pressure drop in 24 hours. Will that happen with this storm? It remains to be seen, but it’s quite likely.

On the upper air map, you’ll see a large, powerful trough digging south over the Carolinas. That trough will rapidly strengthen, undergoing bombogenesis as it pull north. Look at all the energy, shown in the orange and red colors, off the coast of Georgia and Florida.

What Causes Bombogenesis?

There’s one major feature on the above map that jumps out at me. See the corridor of strong winds that stretches from northern Mexico to the southern tip of Florida? That’s the subtropical jet, which serves two purposes here.

1. Funnels a nearly endless stream of rich tropical moisture from the Gulf of Mexico into the developing bomb cyclone.
2. Exerts a west-to-east force on the southern edge of the nor’easter, which accelerates the spin of the upper-level low.

Both influences will have significant impacts on rain and snowfall totals, as well as wind speeds. We’ll dive into those details shortly. Furthermore, even without the subtropical jet, the storm will track pretty much right over the Gulf Stream. The Gulf Stream alone provides more than enough fuel for the storm to rapidly strengthen and maintain itself.

Similarities to the October, 2021 Bomb Cyclone

So just how similar are the meteorological setups between this storm and the October nor’easter?

• Both storms are bomb cyclones
• They both formed off the coast of Georgia and the Carolinas
• There is an immense amount of tropical moisture to tap into from the Gulf Stream
• Steering currents are nearly identical

This Bomb Cyclone will not Impact New England like the October Storm Did

The greatest impact of the October storm was the widespread power outages. As a New England native, I’ve been through some monster storms over the years. I’ve never seen power outages and downed trees anywhere close to the magnitude we saw following the October nor’easter.

Thankfully, it’s extremely unlikely you’ll see anything remotely close to the magnitude of power outages in October. The biggest difference is that the leaves are no longer on the trees. As a result, the surface area of the trees is far less, meaning that it takes much greater winds to do the same amount of damage. Additionally, the most vulnerable limbs, branches, and trees came down in the October storm. This time around, trees and limbs won’t come down nearly as easily. Don’t get complacent, though. The risk of power outages is definitely there with this storm.

However, where you may dodge one bullet, there are others you’ll have to content with. The shift from fall into winter brings in much colder air. The precipitation in the October storm all fell as rain. This time around, you’ll be dealing with snow. And lots of it.

A Better Storm For Comparison

In fact, for a much similar storm, forget the October nor’easter. Instead, go back to exactly 7 years ago today – 27 January, 2015. That day, the first Blizzard of 2015 dumped over 3 feet of snow across southern New England. It kicked off an infamous snowmageddon winter, that plunged the region into a months-long deep freeze.

All right, enough history. Let’s dive into the models.

Model Comparison: Bomb Cyclone Track and Timing

Let’s look at the same models we did with our analysis of Hurricanes Henri and Ida last summer. If you’ve forgotten those models, here they are.

For tracking and timing, you want to focus on the position of the center of the surface low, denoted by the red “L” on the map. In addition, note the timestamp on the upper left corner of the map. Those timestamps are in Zulu time, or UTC. Eastern time is 5 hours behind UTC. Don’t worry about the wind barbs for now. We’ll look at those in much more detail shortly. Click on any image to view it in full size.

As you can see, the American, European, and Canadian models are in very close agreement with each other. They show the the low passing just offshore of Cape Cod and the Islands around 00Z on Sunday (7 PM EST Saturday). The UKMET shouldn’t be discounted, either. It’s timing agrees with the other three models. Steering currents over the Appalachians can easily push the storm further offshore. However, it’s unlikely that it will pass any closer to the coast than what the GFS, ECMWF, or GDPS indicate.

Model Comparison: Bomb Cyclone Intensity (Pressure)

All right, it’s time to answer the million dollar question: will this storm bomb? To do this, we’ll need to figure out when each model expects the storm to reach its peak intensity, or minimum pressure. Then, we’ll compare the pressure at its peak intensity to the pressure 24 hours earlier. Remember, in order for a storm to be considered a bomb cyclone, it must undergo a 24 millibar pressure drop in 24 hours. Here is when each model expects the storm to reach its peak intensity.

Now, all we need to do is compare it to the same plots 24 hours earlier.

So do the models expect the storm to bomb? Here are their official predictions.

Models are usually not this assertive, but that’s a pretty definitive yes. The storm will bomb. Cue Toots and the Maytals.

Wind Forecast

Whenever a nor’easter undergoes bombogenesis, one thing is assured: there will be wind. Lots of it. So just how much wind will there be? You probably remember the October bomb cyclone, which brought 100-plus mph (160 km/h) wind gusts to southeastern Massachusetts. Thankfully, I’ve got some good news for you: you won’t see winds like that with this storm.

Look North to Canada for the Best Indicators of Potential Wind Speeds

The fiercest nor’easters get their winds from the pressure gradient between the bombing low and a strong high pressure system over southern Québec. But have a look at this. The high over Québec is much further north and east than it traditionally is for the really bad storms. In fact, it’s not over Québec at all. It’s actually over Newfoundland and Labrador.

Because the high is further away, the pressure gradient won’t be as tight. As a result, wind speeds won’t be as high as they would have been had the high been closer. Don’t get me wrong, it’s still a tight pressure gradient, and you’ll still get plenty of wind. It just won’t be as bad as it could have been. Combined with the expectation that the center of the low will pass offshore instead of right over Cape Cod and the Islands, I expect winds to be less than the bomb cyclone that hit New England last October. Let’s look at the models.

When I look at the models’ wind predictions, I prefer to look at the sustained winds about 400 to 500 meters above the ground, at 925 mb. In coastal areas, models can sometimes underestimate wind speeds when they try to calculate how friction and terrain impact the wind as it comes off the ocean. The 925 mb (400-500 meter) predictions remove those possible anomalies, and also give you the maximum potential wind speeds.

How Much Wind to Expect in New England

In the wind forecasts above, I don’t see any plausible scenario where the ECMWF (European) model forecast verifies. You just simply aren’t going to get winds that strong that far inland. Using the other three models, it’s clear that the strongest winds will be contained to the immediate coastal areas.

Areas that are exposed to the north along the South Shore and the Cape and Islands will see the greatest impacts from the wind. You’ll find the strongest winds on the Cape and Islands. Right now, my best guess is that sustained winds will peak in the 40-50 knot range in exposed areas across the Cape and Islands. Hurricane-force gusts are certainly possible, but I don’t expect anything close to the 100 mph gusts that ripped through during the October storm.

Temperature and Wind Chill: How Cold will the Bomb Cyclone Get?

Despite the availability of rich, tropical moisture, the bomb cyclone will have a very well-established cold core by the time it reaches New England. Furthermore, all of New England and the Canadian Maritimes will be on the cold side of the storm as it passes by. As a result, you should expect bitterly cold wind chills during the bomb cyclone. The models are all in agreement.

Expected Temperatures

Expected Wind Chills

When looking at temperatures and wind chills, you really need to look at the coast vs inland. Even in extreme conditions, the ocean still helps regulate temperatures near the coast. That being said, with the exception of Martha’s Vineyard, Nantucket, and possibly parts of the outer Cape, wind chills will struggle to get out of the single digits. If you’re inland, you’ll see sub-zero wind chills for pretty much the duration of the event.

Precipitation Type

With strong northerly winds, sub-zero wind chills, and everywhere on the cold side of the system, it should not be a surprise that this will be a snow event. Parts of the outer Cape and the Islands may briefly see a little ice mix in during the warmest part of the storm early Saturday afternoon. Other than that, it will be all snow.

On the models, we’ll look at the maximum temperature in the vertical column of air during the warmest part of the storm. Blue and purple indicates that the entire column is below freezing. You will see snow in those areas. Areas in green may briefly see some ice or sleet mix in early Saturday afternoon before changing back to all snow. That’s a result of air on the warm side of the storm wrapping around the top of the low as it approaches.

The European and British models do not calculate the maximum vertical temperature, so we’ll only consider the American and Canadian models. As you can see, their two predictions are nearly identical.

Snowfall Totals Will Be Measured in Feet, Not Inches

Whenever you have a storm that has both bitterly cold temperatures and an ample fuel supply of rich, tropical moisture, you’re going to get massive snowfall totals. However, there is a bit of a silver lining. All four models are showing noticeably less snow totals than they were yesterday. Unfortunately, they are still showing around two to three feet maximum snowfall totals for this bomb cyclone.

Because the GFS and GDPS models use the Kuchera Ratio, which is the most accurate, to predict snowfall, we’ll give the heaviest weight to those models. However, for a number of reasons, nailing down exact snowfall totals for a precise location is extremely difficult in this scenario.

1. The low still hasn’t really formed yet, so we don’t have any actual data from it to feed into the models.
2. The snowfall gradients are tight. A small wobble in the storm track can make a big difference in the snow totals. For example, take any of the above predictions and shift the snowfall totals 40-50 miles east or west.
3. A westward shift in the storm’s track may mean some areas – particularly parts of the Cape and Islands – may see more ice, sleet, or mixed precipitation on Saturday afternoon, which would reduce snowfall totals. Again here, a small shift in the storm’s track can make a big difference. In this scenario, inland areas would also see greater snowfall totals.
4. An eastern shift in the storm’s track would shift the precipitation shield east, meaning the heaviest snow could fall offshore.

How Much Snow Should You Expect?

We can give equal weight to all four models to determine where the heaviest snow will fall. Given my experience both with the models and with these types of bomb cyclones, I think the heaviest snow will set up in southeastern New England, along and east of the Interstate 95 corridor. Rhode Island will take a pretty good wallop, but will ultimately be spared the worst of the snowfall. Total accumulations will drop rapidly once you get west of I-95.

For the largest snow totals, I think 20 to 24 inches across Bristol and Plymouth Counties in Massachusetts is your safest bet at this point. That swath will likely spread across western Barnstable County (Cape Cod) and up into the far southern suburbs of Boston as well. 28 to 32 inches in a few isolated spots is certainly not out of the question, either, but I am not expecting widespread totals above 2 feet.

Summary

I know there’s a lot of information in this post, so let’s put it into a nice, clean table to summarize everything.

Conclusion

Like many other bomb cyclones, this is certainly a storm that you’re certainly going to want to take seriously. However, New England has certainly gone through far worse in the past. Make sure you stock up on what you’ll need for a few days, and then hunker down at home and enjoy it. The storm is fast moving, so it’ll be in and out in only about 24 hours. Then it’s just a matter of digging out, cleaning up, and getting back to your normal routine.

If you have any questions about anything related to this storm, please let me know in the comments below or reach out to me directly.

The post Wicked Bomb Cyclone Set to Pound New England with Fierce Winds and Heavy Snow appeared first on Matthew Gove Blog.

While the model runs this morning somewhat resemble being in agreement, especially when compared to the runs yesterday morning, the run-to-run differences are still very erratic, so we’re not quite at the stage where we can say for certain it’s going to go to this spot at that strength, but we should know a lot more in the coming days. The most recent model runs have been pushing the storm further offshore, but it’s really important, especially at this stage of the game, not to get involved in chasing the models around.

NHC Forecast: 8 AM EDT Sunday, August 24th

As for the specific models, the European and Canadian models have been much more consistent on both intensity and track from run to run than the GFS has. These models both keep the storm slightly closer to shore in their latest runs than the spaghetti plots above show. The GFS is showing the same thing it did yesterday: the evening run has the storm as a Category 2 hurricane, while the morning run has the storm as a pretty weak pile of mush (shown below). Deferring back to the much more consistent European model, my best guess would put the storm somewhere between the two.

European Model Forecast: 2 AM EDT Friday, August 29 

GFS Forecast (Morning Run): 2 AM EDT Friday, August 29

My guess is that the models will begin to converge on a better solution over the next 24-36 hours or so as they gather more data from the now-formed storm. Right now though, the storm does not appear to be a significant threat to the east coast of the US.

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The latest model runs are still in pretty complete disagreement on both intensity and track for this storm. The general trend of the models is to take the storm northwest towards the east coast of the US and bend it back out to sea. I have seen models take it right up the US east coast, and I have seen models take it east of Bermuda, so it’s impossible to say right now exactly where it will go.

Looking at a couple model runs for the GFS should hammer home exactly how much the storm can vary from run to run. Take a look at the following plots from the GFS run from last night (Friday, August 22 at 8 PM EDT) and early this morning (Saturday, August 23 at 2 AM EDT). You are looking at the 925 mb wind plot (the winds about 1 km up) for next Saturday, August 31st.

GFS Friday Evening Run: Strong Category 1 Hurricane 

GFS Saturday Morning Run: Struggling to be a Tropical Depression

With this type of variance in just one model, it’s impossible to say right now what will happen, but I will say this. Looking at the other model runs, the potential is certainly there to get a hurricane off the east coast of the US, but because it’s an El Nino year (which helps hinder Atlantic tropical cyclone activity) and it has been a cool summer across the eastern US, leaning towards a weaker system would probably be the best bet at this time. However, there’s not much we can say for certain right now until both the tropical cyclone forms and the models begin to resemble some form of agreeing with each other.

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So let’s have a quick look at what might be in store for Arthur. This early in the season, sea surface temperatures play a critical role in the health and lifespan of tropical cyclones since water temperatures are so cold from about Virginia northward.

Sea Surface Temperatures – Tuesday, July 2nd

Because of the cold sea surface temperatures (the blue color on the map), ranging from about 60 to 75°F, Arthur will not hold together as a hurricane if it hugs the coast on its journey northward, and will rapidly weaken north of the Outer Banks. Remember that tropical cyclones generally require sea surface temperatures above 85°F to be able to maintain themselves or intensify.

However, if Arthur remains further offshore, it may be able to tap into the Gulf Stream (the wedge of warm sea surface temperatures extending northeast from the Outer Banks). If this happens, it has a much better chance of maintaining hurricane intensity as it progresses northward. This is why the Hurricane Center maintains Arthur as a hurricane so far north. However, a slight deviation left or right would put the storm over much colder waters. Either way this is good news for the east coast.

The other important factor to consider with any tropical cyclone is wind shear. The plots below show shear and shear tendency. There does not appear to be much by the way of significant wind shear in Arthur’s forecast path right now and the tendencies are for the shear to decrease, which would favor the storm to strengthen before it gets to the cold water.

Wind Shear: Tuesday Morning, July 2nd

 

Shear Tendency: Tuesday Morning, July 2nd

I do want to note that the jet stream is forecast to be near the northeast coast of the US by the time Arthur gets up that way. There are several things that could happen as the two begin to interact. The most likely thing to happen is that Arthur will transition to extratropical and essentially become a nor’easter as it is absorbed into the jet stream. This would bring gusty winds and heavy rains to the east coast, and especially to New England. Forecast soundings from Chatham, MA are currently showing sustained winds out of the northwest at anywhere from 15 to 45 mph at Arthur’s closest pass.

GFS Surface Wind/Pressure: Saturday at 2 AM EDT 

GFS 500 mb Wind/Height: Saturday at 2 AM EDT

Right now, the only area that’s really under the gun from this storm is the Outer Banks of North Carolina, which will likely see either strong tropical storm or minimum Category 1 hurricane conditions. After that, the storm will likely move offshore, but if it deviates closer to the coast, it will be over much colder waters and will have a very hard time staying together.

The post A Quick Look at Tropical Storm Arthur appeared first on Matthew Gove Blog.

GOES Satellite Image – Friday at 6:30 AM CST/4:30 AM PST

Storm Brings Much-Needed Rain to Drought-Stricken California

The best news is that this storm will bring some much-needed rain to the areas in California that have been hit so hard by drought this winter. May areas from the Central Valley area all the way down the Interstate 5 corridor to the Mexican border could see up to 2 inches of rain. Temperatures in the valleys and at the coast will be in the 40s and 50s, so winter weather is not a threat at the lower elevations. Unfortunately, whenever you get a large amount of rain falling over a drought-stricken area in a short period of time, flash flooding and landslides will be a concern, especially in areas recently impacted by wildfires.

Conditions up in the mountains will be a vastly different story. Strong winds and heavy snow will create dangerous conditions across the Sierra Nevadas to the south and southeast of Lake Tahoe, including Yosemite National Park and Mammoth Lakes. A Winter Storm Warning is in effect for much of these areas above 6,000 feet until 4 PM PST Saturday. With wind gusts up to 80 mph possible and and snow accumulations of 12 to 24 inches possible, it would not surprise me if this was upgraded to a Blizzard Warning later on. Further to the south where snow is less of a threat, a High Wind Warning is in effect for the Kern County Mountains and the Interstate 5 corridor through The Grapevine until 4 PM PST today. South winds of 30-50 mph with gusts to 90 mph are possible.

GFS Forecast Rainfall/Liquid Equivalent Through 4 AM PST Sunday

What Lies Ahead for this Storm After California

Like many of these storms, it will weaken as it crosses the Rocky Mountains and its supply of moisture is cut off. As it ejects over the southern plains, it will interact with an Arctic airmass plunging southbound out of Canada. As a result, it will bring light winter precipitation (snow, sleet, and freezing rain) and a cold rain to parts of Kansas, Oklahoma, and north Texas. In Oklahoma, freezing rain and sleet will be the primary modes of precipitation, with up to 1/10 of an inch of ice accumulations possible with locally higher totals, especially across eastern Oklahoma. Heavier snow totals will be possible up in Kansas, with mainly rain to the south down in Texas.

The storm will continue to move to the ENE once it crosses the central and southern plains. The exact location, timing, and intensity of the storm once it reaches the east coast is still very much up in the air, so stay tuned. Right now, there is the potential for heavy snow near the east coast, but it appears to be confined to a fairly localized area if it does indeed happen. The models should be able to get a much better grip on the storm once it comes ashore and the Weather Service can get accurate data from inside of it.

The post Beautiful and Impressive Storm Coming Ashore in California appeared first on Matthew Gove Blog.

Outlook for New England

A weak disturbance has been tracking eastbound down Interstate 40 for the past few days. That system dropped 1 to 3 inches of snow on Friday over parts of eastern Oklahoma, Arkansas, and North Texas. As of 7 AM EST today, the upper-level disturbance was centered near Memphis, Tennessee, and should be centered near the Tennesee – North Carolina border by daybreak on Sunday. Temperatures south of northern Virginia will be above freezing, so any precipitation will fall as rain the Carolinas Sunday morning. Any precipitation that falls will be very light, if it falls at all. The heavier precipitation will be well offshore.

Also beginning Sunday morning, a surface low will begin to develop off the Mid-Atlantic coast. Some of the GFS runs from earlier today brought the system right up the east coast, but this morning’s run is much more in agreement with the Eurpoean model. Both models are now showing the surface low developing well offshore and moving northeast, staying sufficiently offshore of the east coast of both the United States and Canada. The surface low is being “sling-shotted” around the upper-level trough, so it is moving faster and will be further offshore than models earlier this week were showing.

Sfc Wind/Pressure/Precip – Saturday at 7 PM EST

The storm may pass close enough to the coast to bring some gusty winds and light snow to eastern New England, but this will not be major system, and I am not anticipating any significant travel issues at this time. Wind gusts could be as high as 20-25 knots, and any snow accumulations will be minimal (less than 1 inch).

Another surface low may develop just south of New England late Sunday night into Monday and rapidly move northeast. This system could bring 20-30 knot winds and a few inches of snow to southern New England. Precipitation should end by Monday afternoon, but some gusty winds may remain through Monday night. The models are not in agreement with this system (some don’t even develop this low at all), so stay tuned.

Sfc Wind/Pressure – Monday at 1 AM EST

Southern Plains

After another Arctic cold front comes racing down the plains on Sunday, another disturbance will eject across the southern plains on Monday. Models are currently hinting that any precipitation that falls Monday morning along and south of Interstate 40 in Oklahoma may start as a winter mix before quickly changing over to all snow. Forecast soundings from the Oklahoma City Metro are showing that this changeover could occur as soon as sunrise, and depending on exactly when the precipitation starts, it could just start as snow, too.

Further to the south, a much deeper mid-level warm layer will be present, which will delay the changeover to snow to later in the day. Areas right along the Red River may not even make the transition at all. The good news is that the bulk of the precipitation should fall well north of this area, so widespread significant icing is unlikely. The highest precipitation totals appear to be in the NW, NE, and SE quadrants of Oklahoma, including the entire Oklahoma City Metro, and much of Arkansas. This could change as we get closer to the event, however.

As far as snowfall totals go, I would expect to see a lot of reports in the 1 to 3 inch or 2 to 4 inch range, but it’s still too early to talk specifics on exact locations. The Oklahoma City Metro will likely once again be right on the edge of lighter snow and heavier snow, so a small shift in track could mean a big difference in snow totals. A few isolated 5 to 6 inch totals may pop up in eastern Oklahoma and northern Arkansas. Keep in mind that these will likely change as the event approaches and things start to come into focus a bit better, so stay tuned for more.

The post Winter Weather Outlook for Sunday Through Tuesday appeared first on Matthew Gove Blog.

Tuesday, February 4th: Boston, MA and Washington, DC

The winter storm that passed through Oklahoma on Sunday is currently centered over the Tennessee valley and will be well offshore by sunrise on Tuesday, and will bring precipitations along the coast of the Mid-Atlantic and Southern New England. Areas north of the Mason-Dixon Line could see a few more inches of snow, with some isolated higher totals possible, especially along the Connecticut coast and Long Island. All precipitation will end by 11 PM EST tonight.

The second winter storm will eject over the southern plains from the Rockies tonight and will be moving rapidly to the east/northeast on Tuesday. This storm will be approaching the east coast by Wednesday morning. I’ll start by looking at the GFS model output of the big picture, and one of my favorite winter weather plots, the maximum temperature in the precipitation column (surface to 500 mb), which is a great way to help determine what type of precipitation will fall. If you are north of the thick black line (the 0°C max temp line), you will get snow. South of it, we will need to look at surface temperatures and soundings to determing the type of precipitation.

 500 mb Wind/Height – Tuesday at 7 PM EST

The Boston area will not see any precipitation between about 7 PM EST Monday and 7 AM EST Wednesday. In Washington, DC, precipitation should start between 10 PM EST Tuesday and 1 AM EST Wednesday. Since we are looking at one specific location, let’s fast forward and look at a couple soundings from Washington, DC after daybreak on Wednesday. Precipitation will end in Washington by midday Wednesday

Washington, DC Forecast Sounding – 7 AM EST Wednesday

The most significant feature I notice on these soundings is that the low-level temperatures all stay above freezing, so any precipitation that falls will fall as a cold rain. However, I should note that the surface temperatures are very close to freezing, so just a few degree drop in surface temperature could result in freezing rain instead.

Thursday, February 6th: Washington, DC and Raleigh, NC

Things appear to quiet down for at least a few days beginning on Thursday. I do not anticipate any travel problems on Thursday, as skies will clear overnight Wednesday in both Washington and Raleigh, and temperatures will fall into the 20’s and 30’s. Skies will be partly cloudy by sunrise on Thursday, with high temps in the 40’s across all of North Carolina on Thursday.

Sunday, Feburary 9th: Raleigh, NC and Boston, MA

Before I even begin, I do want to point out that Sunday is still 6 days away, so confidence in this forecast is low. A powerful upper-level low is set to come off the Rockies and eject across the southern plains on Saturday, bringing more wintry precipitation to parts of Kansas, Oklahoma, and Texas. This storm is taking a much more southerly track than the previous two, which will likely allow it to tap into rich, Gulf of Mexico moisture. Models are currently showing the upper-level low centered near Dallas, TX at 7 AM EST on Sunday, and the surface low centered over Alabama. Below you will find the ECMWF model output for Sunday at 7 AM EST. Do take note that this setup is screaming “Textbook Significant Coastal Storm” at me, but it will likely not begin to impact the coast before Sunday night.

ECMWF Forecast – 7 AM EST Sunday, Feb. 9th

The nice thing about storms that track further south is that the warm sector is plenty warm, which will keep temperatures in North Carolina well above freezing on Sunday. There will likely be rain around on Sunday, but I do not anticipate wintry precipitation at this time, but be aware that things could change between now and Sunday.

Further up the coast in Boston, it will be cold, but there will not be any precipitation at all on Sunday. Models are showing the developing nor’easter starting to move up the coast on Sunday night, with precipitation moving into the Boston area between midnight and 3 AM EST on Monday. Again, I want to reiterate that this is still close to a week away and that things will change between now and them, so I will be posting further updates as I gain confidence in the forecasts. I’ll leave you with the ECMWF model forecast for 7 AM EST on Monday, Feb. 10th, which reinforces the setup screaming “Big Time Coastal Storm.”

ECMWF Forecast – 7 AM EST Monday, Feb 10th

I will be posting forecasts for Oklahoma later this week as this storm approaches.

The post A Look at the East Coast Weather for the Next Week appeared first on Matthew Gove Blog.

Northern Gulf Coast

One of the trickiest aspect of a winter storm forecast this far south is to figure out just exactly how the warm sea surface temperatures will affect the coastal temperatures and precipitation types. Water temperatures along the northern Gulf Coast are in the 50s, which is plenty warm enough to impact the precipitation type at the coast. Models are currently showing that the snow/freezing rain line will be well north of the Gulf Coast on Tuesday evening, situated roughly along a line from Lake Charles, LA to Hattiesburg, MS to Columbus, GA. With the timing of the precipitation, I would expect coastal areas to see primarily sleet and freezing rain, since the precipitation should end at the coast before the mid levels of the atmosphere get cold enough to change the precipitation over to snow.

The coastal locales that are most likely to see snow are the areas between New Orleans, LA and Pensacola, FL. Atmospheric profiles may get cold enough for a change over to snow to occur shortly before the precipitation ends, so any accumulations will be minimal, if they occur at all. Coastal snow could fall as far east as Panama City, FL. The window for snow at the coast appears to be between 9 PM CST Tuesday and 3 AM CST Wednesday.

Further inland, areas along and north of Interstate 10 are much more likely to see accumulating snow. Atmospheric profiles there will be cold enough for it to snow, and with a driving north wind, those areas will not be affected by thermal radiation coming off the warm waters of the Gulf. Models are currently show a 1 to 3 inch swath of snow accumulations falling between Slidell, LA and Pensacola, FL. That swath is surrounded by an area of up to 1 inch accumulations between Baton Rouge, LA and Fort Walton Beach, FL, extending up into southeast Alabama and southwest Georgia. Snow could fall as far north as a line from Houston, TX to Jackson, MS to Birmingham, AL. Temperatures will quickly warm later in the week, so any snow and ice accumulations will not last very long.

Georgia and The Carolinas

The North and South Carolina coasts appear to be on tap to absorb the brunt of this storm. Atmospheric profiles along and north of a line from Savannah, GA to Panama City, FL should be cold enough for precipitation to fall as snow. The winter storm will have plenty of moisture available after tapping into the Gulf of Mexico moisture, but it will also have an ample supply of moisture available off the southeast coast, especially with the Gulf Stream so close by.

Soundings along the Carolina coasts are textbook winter weather soundings. There will likely be a warm layer around 4,000 feet over the South Carolina coast when the precipitation first starts falling, so it may start as sleet and freezing rain before changing over to snow. Over North Carolina, however, all layers will be below freezing from the outset, so it may start as a wintry mix before changing over to snow. Any sleet and freezing rain that falls will reduce snow totals, which could greatly affect snowfall totals in the Carolinas.

Models are currently showing that the coastal snow will fall between Savannah, GA and the southern tip of the Delmarva. Unlike the northern Gulf Coast, the duration of the precipitation will be much longer on the Carolina coast. Precipitation should really start cranking up around 7 or 8 AM EST on Tuesday and should last for about 24 hours. Models are showing impressive snowfall totals for the coastal areas, but I think they may be a little agressive. Some areas between Wilmington, NC and the Pamlico River could see up to a foot of snow, but I would expect to see most totals in the 4 to 8 inch range. Snowfall totals between 2 and 8 inches are possible between Charleston, SC and the North Carolina/Virginia border.

Further, inland, areas east of Interstate 95 between Richmond, VA and the South Carolina/Georgia border could see 2 to 6 inches, and 1 to 2 inch totals are possible across much of the remaining areas of North Carolina, South Carolina, and northeast Georgia. Just remember that there are a lot of variables in play for these complex forecasts, so the duration of any freezing rain and sleet that falls will have a significant impact on snowfall totals. This is one of those storms that could be a big snowstorm or a big ice storm, so stay tuned to your local news or weather bureau for the latest information.

The post Rare Winter Storm to Impact the Gulf Coast and Deep South appeared first on Matthew Gove Blog.

Once again, predicting exactly what type and how much precipitation at any given location. Things should become a lot clearer in the next couple days, especially after the front comes through overnight tonight. Right now, it looks like the snow/winter mix line will initially set up shop just south and east of Interstate 44 and will slide southeast as colder air filters into the mid-levels behind the front. The graphics below indicate the maximum temperature in the cloud and precipitation layer, and the snow/winter mix line will be near the 0°C line, which is highlighted in thick black.

 Sfc-500 mb Max Temp (°C), Thurs at 12 Noon CST

For Oklahoma, any precipitation that falls north and west of that 0°C line will fall as snow, and anything that falls south and east of that line will fall as sleet or freezing rain (and even rain in the far southeast part of the state).

Since the snow/winter mix line will initially set up so close to the Oklahoma City area, let’s take a look at some forecast soundings for Norman, for Thursday at Noon CST (left) and Friday at 6 AM CST (right).

 

According to the GFS model, on Thursday afternoon, a thin layer of above-freezing temperatures will be present between about 850 and 750 mb. Any snow that passes through this layer will melt before refreezing below 850 mb (about 4500 feet), resulting in sleet in the Norman area, which may start as freezing rain. That same layer will also be a lot drier than the any of the surrounding layers, which could result in some evaporation and less precipitation reaching the ground.

The changeover from sleet to snow should occur between Midnight and 3 AM CST on Friday, as the warm layer cools below freezing, and precipitation in the Norman area should be all snow by 6 AM CST Friday. Exactly how much snowfall we get is still to be determined. Models are in pretty good agreement that the maximum snow growth zone, which occurs between -20°C and -10°C, will be somewhere near 500 mb, but there is still some disagreement as to where the area of maximum lift will be. Some models match up the area of maximum lift with the maximum snow growth zone, while some place the area of maximum lift well below it. If the two areas match up, the area will see higher snowfall totals, but that remains to be seen.

Exact snowfall totals will also depend on when the changeover from the winter mix to snow occurs. More sleet and freezing rain will result in less snowfall. I will go with a slightly conservative initial guess of 1 to 4 inches of snow, depending on exactly where you are, but those numbers could easily go up. Areas of southern and southeastern Oklahoma are more likely to see an ice storm than a snow storm. Nearly all Oklahoma counties along and south/east of a line from Lawton to El Reno to Ponca City are under a Winter Storm Watch already, so stay tuned for more info. I will be back with another update later this afternoon/evening.

The post Another Tricky Winter Forecast for Oklahoma appeared first on Matthew Gove Blog.

Behind the front, winds are light out of the northwest at 5-15 knots for nearly all coastal areas between New Jersey and Florida. Temperatures across interior New England down through the mid-Atlantic States are mainly in the upper 30’s and low 40’s. At Noon EST, the freezing line was located approximately along a line extending from Buffalo to Pittsburgh to near Beckley, WV (in the SE part of the state). It will be snowing along and west of that line. As the freezing line moves east, the precipitation will be pulling out of those areas, so coastal areas will see very little snow, if any at all. Areas in the Appalachians back into parts of the Ohio Valley, however could see as much as 6 inches of snow, with some higher totals near the Canadian Border in New York.

Barring something really crazy happening (which I am not anticipating at this point), this will be my last update on this storm, as I will be signing off for the Thanksgiving holiday and will not be back until next week. If you want any further details, the model data from a couple days ago still looks pretty much on track for this storm. Once this storm exits your area, calm and sunny weather will come in behind it. This weekend looks pretty nice for nearly the entire country. Have a great Thanksgiving and be safe if you are traveling.

The post Quick Update: Thanksgiving East Coast Storm appeared first on Matthew Gove Blog.