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.

As expected, the upper-level steering currents have pushed Henri back to the east. It looks like the GFS (American) model was right all along. Its consistency and history of being right with Henri is why have been saying over the past three days that Henri will track east of the center of the National Hurricane Center‘s cones.

I still expect Henri to make a left hand turn while it comes ashore, as an upper-level low tries to sling shot the hurricane into Ontario. However, as we discussed yesterday, it will quickly run into a road block from a strong high pressure over Québec, briefly stalling out before being ejected across Northern New England and up into the Canadian Maritimes.

Current Watches and Warnings

The watches and warnings for Henri remain unchanged since yesterday. Hurricane Warnings remain in effect from

• The Massachusetts/Rhode Island State Line to New Haven, CT
• Block Island
• Port Jefferson, NY to the west end of Fire Island, NY

Likewise, Tropical Storm Warnings remain in effect from

• Chatham, MA to the Massachusetts/Rhode Island State Line
• Martha’s Vineyard and Nantucket
• New Haven, CT to Port Jefferson, NY, including all of New York City
• The west end of Fire Island, NY to Point Pleasant, NJ

Storm Threats and the Timing of Each

With Henri’s imminent landfall in southern New England, we are going to shift a bit from discussing exactly where the eye will come ashore to the timing of the threats Henri will bring to the region.

Wind

Because Henri is expected to weaken so rapidly as it starts interacting with the land in southern New England, most places along the south coast will likely see the strongest winds before the storm makes landfall. Even if you remove the effect of the land, Henri is over cool waters, and will be weakening as it approaches the coast.

This timing of the strongest winds is especially true for the eastern half of the storm, primarily from Narragansett Bay to Cape Cod and the Islands. Because Henri has been pushed back tot he east, those locations will likely see stronger winds than were predicted just yesterday. Wind gusts in excess of 50 knots are all but certain, except possibly for the outer portions of Cape Cod. The potential is there to see gusts to 70 knots, but it’s far from a guarantee.

The one exception is in the area immediately around the location that the eye of Henri makes landfall. The eye is expected to pass near Block Island and the far eastern tip of Long Island before coming ashore near the Connecticut/Rhode Island state line.

Storm Surge

Because winds are out of the south (onshore) in the eastern half of the storm, Rhode Island and southeast Massachusetts will bear the brunt of the storm surge. West of Henri’s eye, winds will be out of the north (offshore), with the exception of the north coast of Long Island. However, Long Island Sound is so small compared to the open Atlantic Ocean, storm surge effects on the north shore of Long Island will be less than points further east.

To determine which locations will see the greatest impact from the storm surge, you simply need to look at where the window for the strongest winds overlaps with the timing of high tide. You’ll find the lowest impacts where the strongest winds overlap with low tide, which occurs about 6 hours before and after each high tide. Also, don’t forget that locations closer to the eye tend to see greater impacts than locations on the edge of Henri.

What Does This Table Mean?

Thankfully, there is not one location that really jumps out at me as being much higher risk for storm surge. High tide in most spots in both Narragansett Bay and Buzzards Bay will fall at the beginning of that window of maximum winds, which will help limit the impact of the storm surge. Hyannis is far enough out in the outer part of Henri’s circulation that lower wind speeds will help offset the fact that high tide falls at the end of window of maximum winds. Finally, the Connecticut locations will see most likely see offshore winds. New London may see a brief period of onshore winds this morning, but they will quickly shift as Henri approaches. I would expect to see 3 to 5 foot storm surge in all of the above locations.

Inland Flooding

Based on model guidance and early radar returns, the majority of the rain is in the western Half of Henri. As a result, the highest risk for inland flooding will be in Connecticut, western Massachusetts, southeastern New York, and northern New Jersey. Depending on where Henri stalls out to make its turn to the east, southern Vermont could be at a higher risk for flooding as well. The rest of New England is by no means out of the woods, but is at much lower risk given the sharp gradient in forecast rainfall totals. Remember, if you see flooding, Turn Around, Don’t Drown!

Power Outages

Widespread power outages should be expected across most of Connecticut, Rhode Island, Massachusetts, and Long Island. Downed trees are the #1 cause of power outages in storms like this. New England has had a lot of rain in recent weeks. As a result, the soil is quite saturated, making it easier for Henri to uproot trees. If you see downed power lines, don’t go anywhere near them! Back away and call the electric company.

Be prepared to be without power for a while if you do lose it. We’re talking days here, not hours. But thankfully, barring any unforeseen catastrophes, it shouldn’t be weeks, either, despite some of the reports you may have heard on the news. Further north, it would not surprise me at all to see isolated power outages across parts of Vermont, New Hampshire, and southern Maine.

Conclusion

Hurricane Henri has arrived in southern New England. By now, you should be hunkered down and sheltering in place until the storm passes. Henri will likely be the most significant tropical cyclone to impact southern New England since Hurricane Bob in 1991.

Once Henri makes landfall, it will rapidly weaken. It is expected to be a tropical depression by 2 AM EDT Monday, and will be just a remnant low by midday. However, that should not be taken lightly. Just because the wind diminishes, it does not mean the threat for flooding has dissipated, too. In fact, it’s quite the opposite. Be smart, stay safe, and enjoy the ride.

The post Hurricane Henri in New England: Sunday Morning Outlook appeared first on Matthew Gove Blog.

Big Picture Overview

The primary steering currents that are driving Henri have strengthened since yesterday’s discussion. The low has set up over West Virginia and continues to dig to the south and east. Similarly, the high pressure has firmly established itself over Québec.

Because air moves from areas of high pressure to areas of low, the low pressure system over West Virginia will try to suck Henri into it. You can see the effect in the upper-level steering currents, which the green arrows mark in the plot above. As a result, that low has been responsible for the drastic westward shift in Henri’s forecast track over the past 48 hours or so.

Unfortunately, it’s not as simple as Henri getting sucked into the upper-level steering currents and getting flung up into Ontario. Remember that big ridge of high pressure over Québec? That acts like a roadblock, preventing Henri from moving north and northwest once it makes landfall in southern New England. Furthermore, as the low pressure expands to the south and east as it strengthens, it will actually push Henri back to the east as it tries to pull the hurricane into it.

So what’s the end result? As Henri gets pulled into the low, it will screech to a halt once it hits the blocking effect from the high. As the low pressure system over West Virginia move east, it will eventually grab hold of Henri and eject it out over eastern Massachusetts and up into the Gulf of Maine. If you’ve looked at the 5 AM EDT outlook from the Hurricane Center this morning, that’s why there’s such a big kink in the track. We’ll come back to this shortly.

Current Watches and Warnings for Henri in New England

As of 11 AM EDT, Hurricane Warnings are now in effect from

• The Massachusetts/Rhode Island State Line to New Haven, CT
• Block Island
• Port Jefferson, NY to the west end of Fire Island, NY

Likewise, Tropical Storm Warnings are now in effect from

• Chatham, MA to the Massachusetts/Rhode Island State Line
• Martha’s Vineyard and Nantucket
• New Haven, CT to Port Jefferson, NY, including all of New York City
• The west end of Fire Island, NY to Point Pleasant, NJ

Storm Surge Warnings are also in effect for the entire south coast of New England and Long Island as Henri approaches. While the surge will not be catastrophic, it will likely flood low-lying coastal areas with 3 to 5 foot storm surge. If you live in an area that often floods, I would expect it to flood as Henri comes ashore. Please be aware there will likely be very dangerous rip currents in the warning area as well.

Model Overview

Models are finally converging on a solution after a lot of uncertainty over the past 48 hours. Remember, don’t focus on one particular outcome. Instead, you want to look for patterns. Where do they agree? Where do they disagree? If they disagree, why do they disagree? Are there any anomalous runs that should be immediately discounted? Models that have been consistently accurate that are in agreement are the ones you want to focus on.

The GFS (American) Model

The GFS has been the most stable, consistent, and accurate model over Henri’s lifecycle, so we will once again use it for the basis of our forecast. This morning’s runs remain consistent with both Friday’s and Thursday’s runs. Neither Henri’s track nor strength have changed much in the GFS runs over the past two to three days.

The ECMWF (European) Model

Over the past two or three days, the ECMWF’s strength forecast has been very much an outlier. This morning, it is finally coming into agreement with the other models. It still shows weaker wind speeds at landfall than any of the other models. However, because it is now in close agreement with the other models, we can give it much more weight when we make our official forecast.

The UKMET (United Kingdom) Model

In yesterday’s model run, the track of the UKMET was quite anomalous, tracking much further west than any of the other models. As expected, that too, has largely come back into agreement with the rest of the models this morning.

It’s also worth noting that the UKMET has Henri making landfall sooner and with slightly stronger winds than any of the other models. That’s a result of the model having Henri moving faster. In the UKMET scenario, Henri spends less time over the cooler waters off the coast of New Jersey, and thus has less time to weaken. We will need to take that into account when we make our official forecast.

The GDPS (Canadian) Model

The GDPS has been in lockstep with the GFS for days. This morning, it remains that way, bringing Henri ashore at the Connecticut/Rhode Island state line. Much like the GFS, the GDPS has been very consistent, stable, and accurate over the past few days. As a result, we can use it to make forecasts with a high degree of confidence.

Despite our confidence in the model, this individual snapshot is actually a bit misleading with regards to wind speed. You may look at this map and think, oh boy, that’s in line with the weaker winds of the ECMWF. And that’s true…to a degree. All models have Henri weakening rapidly once it makes landfall on the south coast of New England. If you look at the GDPS snapshot for six hours earlier (Sunday at 8 AM EDT), winds are much stronger.

As a result, much of southern New England and Long Island will likely experience stronger winds than the 2 PM EDT snapshot indicates as the eye of Henri approaches landfall. Additionally, a small uptick in Henri’s forward speed means that it could come ashore with much stronger winds.

Model Summary for Henri in Southern New England

This morning’s model runs are in close agreement with each other. After all of the uncertainty of the past few days, it’s about as good of an agreement as we can ask for. In our official forecast, we’ll be able to give each model close to equal weight and make our forecast with a high degree of confidence.

Our Official Forecast for the Impact of Henri in New England

With the models now aligning with each other, our forecast should be pretty easy to make. However, there is one parameter that I think we can discount. Based on over a decade of experience with working with mathematical models, my meteorological intuition is telling me that there is basically no way that Henri will have 90 mph winds at landfall like the UKMET says. I don’t want to discount its prediction fully, but we’ll give much less weight to it.

Additionally, because Henri is expected to weaken so rapidly once it makes landfall, the greatest coastal wind impacts will likely be felt prior to landfall. This is particularly true for areas in the eastern half of the storm…Rhode Island and southeastern Massachusetts, I’m looking at you here. Flooding will remain a threat until either Henri weakens sufficiently or it exits the area.

Post-Landfall

Henri will continue to be pulled into the upper-level low that currently sits over West Virginia as it approaches landfall. Interestingly, the moment that the sling-shot effect (when a mid-latitude low grabs hold of a hurricane and flings it north) occurs will be at the same time as Henri runs into the road block from the strong high over Québec.

As a result, you’ll see Henri make a sharp left (westward) turn right after landfall, which is from the low trying to fling Henri up into Ontario. It will almost immediately run into the roadblock from the high over Québec and temporarily stall out over northern Connecticut and/or western Massachusetts. As the upper-level low moves east, it will push Henri east with it, eventually sling-shotting it across southern New Hampshire and eastern Massachusetts and up into the Canadian Maritimes.

The National Hurricane Center Forecast

Our forecast remains largely in agreement with the National Hurricane Center. However, from model analysis and my meteorological intuition, I believe that Henri will track slightly east of the center of the official Hurricane Center cone. While I don’t think landfall in western Rhode Island is the most likely outcome at this time, it’s certainly possible. It’s not a major difference, but it certainly could make for an interesting ride on Block Island much of the Rhode Island coast if it verifies.

Conclusion

The picture is certainly coming into focus as Henri approaches Southern New England. It remains a flip of a coin whether Henri will be a tropical storm or a hurricane when it makes landfall, but you will likely see hurricane-force wind gusts across much of southern New England. If you’re in the path of Henri, please stay safe and enjoy the ride. Please let me know if you have any questions, and stay tuned for tomorrow morning’s update.

The post Hurricane Henri in New England: Saturday Morning Outlook appeared first on Matthew Gove Blog.

Big Picture Overview

Before we jump into models, let’s look at the big picture. Here’s what the upper-level winds across the continental US look like. Henri is currently sitting in the bight between the Bahamas and Cape Hatteras.

Looking at the map, there are a couple things that will impact Henri as it churns towards New England.

1. A large ridge of high pressure sits over Ontario and Québec
2. A mini-trough (it’s a little big to call it a shortwave) currently centered over Pittsburgh is passing through the Ohio Valley

So how will they impact Henri? Quite a bit. The high pressure system will slow Henri down as it approaches New England. The mini-trough, which is a weak area of low pressure, will pull Henri towards it. That trough is the culprit behind why the track has so drastically shifted west over the past 24 hours.

Additionally, Henri has been in a sheared environment for the past 24-36 hours. That shear has dissipated, creating very favorable conditions for Henri to strengthen as it moves north.

Current Watches and Warnings for Henri in New England

As expected, the National Hurricane Center issued Hurricane and Tropical Storm watches for southern New England and parts of New York this morning with its 5 AM EDT advisory for Henri.

Hurricane watches extend from Plymouth, MA to New Haven, CT, and include all of Cape Cod and the Islands. If you’re on Long Island, you’re under a hurricane watch if you’re east of a line from Port Jefferson to the west end of Fire Island. Tropical Storm Watches cover the rest of Long Island Sound and the south coast of Long Island. As of right now, New York City is not under any watches, but that will likely change over the next 12 to 24 hours. The same goes for Boston.

What Do The Models Predict for Henri’s Impact in New England

A good forecaster knows how to look at the models and determine which ones to give the most weight to when they make their forecast. I have my favorite collection of models I turn to when forecasting hurricanes. I want to emphasize when you look at the models, don’t focus on one particular outcome. Instead, you want to look for patterns. Where do they agree? Where do they disagree? If they disagree, why do they disagree? Are there any anomalous runs that should be immediately discounted? Models that have been consistently accurate that are in agreement are the ones you want to focus on.

The GFS (American) Model

The GFS has been the most consistently accurate model for both Hurricane Henri as well as Hurricane Grace, which is currently heading towards a second landfall on Mexico’s Gulf Coast after passing over the Yucatán. As a result, we’ll use it as the basis of our forecast to which we can compare the other models. This morning’s runs remain consistent with yesterday’s. The GFS has Henri following a very similar path to Hurricane Bob into southern New England. It makes landfall in Narragansett Bay with wind speeds of 74 knots (85 mph).

The ECMWF (European) Model

The ECMWF has been a bit of an outlier with Henri’s strength, but it has been in lockstep with the GFS for where Henri will track. While you can’t completely discount its wind speed forecast, you will notice that it is noticeably weaker than the other models. However, wind speeds in the ECMWF forecast for Henri have trended up over the past 24 hours, meaning that it will likely align with the GFS as Henri approaches New England.

The UKMET (United Kingdom) Model

While the ECMWF was an outlier for Henri’s strength, the UKMET has done the exact opposite. Its strength forecasts are in strong agreement with the GFS, but its forecast track for Henri has trended much further west than the other models. Interestingly, the UKMET is also showing signs of coming into agreement with the GFS. In its runs just yesterday, the UKMET showed landfall possibly as far west as New Jersey. This morning’s runs have pulled it much further back to the east and closer to both the GFS and the ECMWF tracks.

The GDPS (Canadian) Model

The GDPS has largely been in agreement with the GFS on both strength and track over the past 48 hours. From a forecasting standpoint, that’s a very good thing. It means we can give less weight to the ECMWF’s outlying strength and the UKMET’s outlying track. It also means that we should expect those outliers to align with the rest of the models that are in agreement within the next 36 hours or so.

Model Summary

Before we put our official forecast together, let’s stop and think about which models should get the most weight. Because the GFS (American) and GDPS (Canadian) are in close agreement, we’ll give the most weight to those. Additionally, the ECMWF’s track and the UKMET’s strength are also in close agreement with the other two models, so we can give them plenty of weight as well. As for the outliers, I don’t want to completely discount them because they are trending back towards the models that are all in agreement. If anything, the fact that they’re trending back only reinforces our confidence in the other models.

Our Official Forecast for the Impact of Henri in New England

Based on the models we looked at, along with a little intuition and gut feelings, we can make our own official forecast. Hurricane Henri making landfall is southern New England is all but guaranteed. The big questions are where will it hit, and how strong will it be. Here are our best guesses.

How Does It Compare to the National Hurricane Center’s Advisory?

If we did our forecasting correctly, our forecast should be pretty similar to the National Hurricane Center’s official forecast. Indeed, the center of the National Hurricane Center’s cone of uncertainty brings Henri ashore near the Connecticut/Rhode Island State line as a strong tropical storm.

Conclusion

Henri is a potent tropical cyclone that folks in New England should take seriously. If it makes landfall as a hurricane, it will be the first hurricane to hit New England since Hurricane Bob in 1991. Whether it can actually do that remains a flip of a coin. I’ll be posting daily updates about Henri at least until it makes landfall. Please don’t hesitate to reach out if you have any questions. Be smart and stay safe.

The post Hurricane Henri in New England: Friday Morning Outlook appeared first on Matthew Gove Blog.

I only ran the models out until early May because we need to focus on what’s going to happen in the next two to three weeks, not what’s going to be happening several months in the future. Additionally, model forecasts get less accurate the further into the future you go. This run assumes current social distancing restrictions remain in place through mid-May and does not account for any additional surges or waves of the virus that may occur later this spring, this summer, or this fall.

Don’t forget, you can always get more information about the model and view detailed case data on my COVID-19 Dashboard. Additionally, I will write up a separate post about the mathematics, equations, and methodologies used in my coronavirus model, which I’m hoping to get posted in the next day or two. Stay tuned for additional discussions about each hot zone as more data comes in.

Alberta

Arizona

British Columbia

California

Connecticut

Florida

Georgia

Illinois

Louisiana

Maryland

Massachusetts

Michigan

New Jersey

New York

Ohio

Oklahoma

Ontario

Oregon

Pennsylvania

Québec

Rhode Island

South Dakota

Tennessee

Texas

U.S. Virgin Islands

Washington (State)

After several requests, I updated this post on 16 April, 2020 to include additional states and provinces, bringing the total to 26 plots instead of 24.

Top Photo: Palo Duro Canyon State Park – Amarillo, Texas – August, 2019

The post A Look at the Best-Fit COVID-19 Model Curves for 24 Key States and Provinces 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.

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.

Models are currently showing sustained surface wind speeds between 35 and 45 knots in southeastern New England, and some isolated spots may see sustained winds above 50 knots. The strongest winds appear to be bulls-eyed over Cape Cod, and will spread north into the Gulf of Maine. There will obviously be higher gusts, and some gusts may approach hurricane strength (64 knots) in ares that are exposed to the south and east. The storm will continue to strengthen as it moves up into Canada, so the stronger sustained winds will be more widespread further north.

Winds will start to increase Tuesday night in the northeast. The mid-Atlantic will see the strongest winds early Wednesday morning (about 1 AM to 10 AM EST). Southern New England will see the strongest winds beginning between 3 AM and 6 AM EST Wednesday and will last until late afternoon, but strong winds on Cape Cod and surrounding areas could last until 9 or 10 PM EST before starting to taper off. Winds in Maine and New Brunswick will be strongest between about 9 AM EST Wednesday and about 1 or 2 AM EST on Thursday. A secondary burst of strong sustained winds will occur behind the passage of the cold front, but they will be nowhere near as strong as the main part of the storm (anywhere from 15-30 knots), but could be stronger on Cape Cod and in areas exposed to the north and west.

I will post another quick update this afternoon, but everything appears to be on track right now for wind and rain at the coast with wintry precipitation over the Appalachians.

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

Part I: Rain and Wind

As a vigorous upper-level trough moves into the northeast, it will help strengthen a potent surface low moving up the coast. Since we are so early in the winter season, the water temperatures off the Georgia and Florida coasts are still warm, so the storm will pull plenty of warm air up with it. A pounding onshore wind will advect these warm temperatures into the coastal areas, resulting in temperatures in the 40s and 50s. Models are showing 925 mb (about 1500 feet) winds between 60 and 90 knots, which will likely translate into sustained surface winds somewhere between 30 and 40 knots with higher gusts (models are in agreement for winds at 925 mb, but vary at the surface). It would not surprise me to see a wind gust or two approaching hurricane strength (64 kts/74 mph) in some of the more exposed areas.

Forecast Surface Temps – Weds at 1 PM EST 

 

Forecast 925 mb Wind/Heights – Weds at 1 PM EST

In addition to the warm air, the storm will also pull a lot of tropical moisture up with it. Dewpoints will be in the 50s, and may approach 60 in some areas. With so much moisture in place, all areas will see at least an inch of rain. There will be widespread 2-3 inch rain totals across much of the northeast, as well as some isolated higher totals.

Forecast Dewpoints – Weds at 1 PM EST

Part II: The Cold

As with any mid-latitude storm system, there is a cold side of the storm, too. The cold air and moisture will align inland to bring wintry precipitation to the Appalachians, but the storm’s dry slot will be situated over the coastal areas when the cold air moves in. A few snow flurries are certainly possible in these areas, but widespread wintry precipitation at the coast appears unlikely.

Forecast Temperature – Thurs at 1 PM EST 

 

Forecast Snow Depth – Thurs at 1 PM EST

The cold front will cross the coastline sometime Thursday afternoon. Temperatures behind the front will for the most part be in the 20s and 30s, with some inland areas dipping down into the teens. Friday will be cold up and down the east coast, but temperatures will start to moderate over the weekend.

So to summarize, Wednesday will be a wind and rain event at the coast, with snow falling in the Appalachians. Precipitation will end on Wednesday night and be followed by the passage of a cold front on Thursday. Friday will be cold but dry before temperatures begin to rebound over the weekend. Stay tuned for more information over the next few days, as things can change quickly with these storms.

The post Coastal Storm Getting Set to Impact the East Coast appeared first on Matthew Gove Blog.

A weak wave of energy is currently crossing Colorado’s Rocky Mountains and is forecast to undergo “lee cyclogenesis” (it’s actually more of a lee intensification) as it ejects off the Front Range and into the Great Plains on Thursday, ahead of a much more powerful upper level storm system moving into the southwestern US. If you still have my Winter Storm notes, this falls into the “Overrunning” category of winter storm. Unseasonably warm temperatures and high dewpoints currently sit across the Central/Southern Plains and Ohio Valley. Expect this cyclone to intensify as it travels through this rich fuel supply and head towards New England.

Adding to the complexity of this forecast is the presence of energy in the subtropical jet (or southern branch of the jet), which is forecast to be sitting along the northern Gulf Coast by 12 UTC/7 AM EST on Friday. As that wave of energy moves across Gulf Coast/Northern Florida, both GFS and ECMWF are forecasting development of a surface cyclone off the coast of the Carolinas, giving you a Miller A Type system, which will be very rich with Gulf of Mexico and Subtropical Atlantic moisture. The surface cyclone from the Miller A system will then merge with the surface cyclone from the Overrunning system coming out of the Ohio Valley, and be driven by the strong upper-level cyclone from the Overrunning system. Coupled with the very high amount of moisture both systems have access to, this leaves the probability of all hell being unleashed somewhere in the northeast quite high (the figures below are from GFS).

500 mb Wind and Heights 

Impacts to the Northeast

Let’s switch gears and take a look at the European Model (ECMWF) for Saturday at 12 UTC (7 AM EST).

You can probably see the combined surface low (upper right panel) looks pretty impressive. Both GFS and ECMWF have it at 992 mb, which is a pretty healthy low, but not crazy. To put it into perspective, your run-of-the-mill Category 1 Hurricanes are usually in the 970-980 mb range. Two surface highs of 1032 mb are forecast to sit over central Quebec and southern Michigan. This 40 mb difference will lead to a sharp pressure gradient, so expect lots of wind. GFS is showing 55-65 knot winds over Cape Cod at 12 UTC/7 AM EST Saturday. Depending on where exactly the surface cyclone passes, winds will be out of either the northeast, north, or northwest. The upper level cyclone (upper left panel) should be healthy as well.

The panels that have me the most concerned are the two bottom panels, which show relative humidity at 700 mb (left) and 850 mb (right). Both levels are absolutely loaded with moisture, so if temperatures and lift (which will be discussed next) are in the right place, this storm could be crippling.

Temperatures, Precipitation, and Accumulation

Before we even think about precipitation type and accumulations, we need to look at temperatures to make sure it is cold enough to support snow. The easiest way is to take a look at a couple of forecast soundings.

 00Z Saturday/7 PM EST Friday

12Z/7 AM EST Saturday

There is a thin warm layer at the surface on Friday evening…don’t let that fool you. Temperatures will cool in the evening with the daytime heating cycle, and will then cool even further with the passage of a cold front overnight Friday into Saturday. Depending on exactly when precipitation starts, it may start as rain/sleet/freezing rain, but I would expect it to change over to snow sometime before midnight EST. It is important to note that the Friday evening sounding is prior to the passage of the cold front, while Saturday morning is after the cold front passes. If you’re wondering how I know this, look at the wind profile on the right hand side of the sounding (below 700 mb). On Friday evening, the wind direction veers (turns clockwise) with height, which indicates warm temperature advection (don’t be fooled…this is a very common feature ahead of cold fronts). On Saturday morning, you have the exact opposite. The wind direction backs (turns counterclockwise) with height, which is indicative of cold temperature advection.

The Saturday morning sounding is a textbook winter weather sounding (don’t hesitate to compare these to the Blizzard of ’05 soundings in my notes). The whole profile is below freezing, so I expect precipitation to fall as snow. If you go back to my notes, you will remember something called the “Snow Growth Zone,” which can be found between -18°C and -12°C. On Saturday morning, this zone can be found just above 700 mb. If lift can be maximized just below the “Snow Growth Zone,” the probability of being absolutely dumped on goes up significantly. Don’t forget, too, that the axis of heaviest snow generally follows the track of the 700 mb low.

So let’s now take a look at lift. The GFS conveniently plots vertical velocity along with height contours at 700 mb, so let’s take a look at it.

You can probably see that the 700 mb low tracks pretty much right over Cape Cod, with the area of maximum lift in the orange just southwest of the Cape. This means you’re gonna see plenty of snow. Like I mentioned in my notes, forecasting total accumulations is very difficult, so I will defer to the National Weather Service for that. They are currently (at about 5:30 PM EST) calling for 10-14 inches on the western end of Cape Cod, and for 14-18 inches on the west sides of Buzzards Bay back into Rhode Island. Current watches and warnings are as follows (the NWS just released a discussion saying that the Winter Storm Watch has been cancelled and replaced with a Blizzard Watch for the entire region, which includes Cape Cod and the Islands):

The Verdict

I would expect this to be a pretty significant storm. It certainly has the potential to rival the Blizzard of ’05, but I really don’t think it will. The low pressure systems are too close together in the vertical direction to really be able unleash their full fury. My gut is telling me you will be on the upper end of the 10-14 inch accumulation range, but things can change. The winds will be the greatest concern. I would expect to see winds close to hurricane force (if not above) for an extended period of time, which result in dangerous wind chills between 0 and 10°F. The good news, though, is that the system is moving pretty fast so it will be in and out quickly.

Originally Written Wednesday, February 6, 2013 at 5:00 PM CST /6:00 PM EST/

The post EXAMPLE FORECAST: New England Winter Storm: February 8-10, 2013 appeared first on Matthew Gove Blog.