Helo my name is Brandon Brady and I am a weather blogger on zoomradar.com. I have been writing several blogs that pertain to summer type weather and climate events. I live in South Florida presently where temperatures from may to October routinely reach 90 degrees or higher diurnally(daily) and upper 70s to 80 nocturnally(night). I want to blog about the Northeastern storm storms and the Low Pressures associated with them that bring an array of precipitation the the mid-atlantic and northeast. I am originally from a town called Waterbury in the State of Connecticut and I am well experienced in winter storms and I actually miss these storms because well it weather and I love all weather even severe weather and that includes snow and winter precipitation.
I am going to write about Different Types of Low pressures in the winter that affect the Eastern States, where they originate, the types of precipitation the Low pressures bring, and Characteristics of Blizzards. I know it is still summer but I look forward in covering several winter storms this year as a meteorologist. Let’s begin. Before I get into all the type of Low pressure systems in winter time, I want to give you basic information about how the Polar jet stream works hand in hand with these Lows.
STORMS and THE JETSTREAM –
Mid Latitude and severe storms follow the path of the shifting Polar Front Jetstream. If the Jetstream is in a zonal path or flow, Low Pressure systems don’t have enough time to form, and if they do they are weak and bring limited precipitation either rain or snow or mixed precipitation. The zonal flow is straight west to east and very fast, the reason for the west to east flow is due to the WESTERLIES – bands of wind between 30-60 degrees of Latitude on either hemisphere that blow in a west direction. Yes storms follow this wind. If the jet stream is meridional or amplified coming from the North and driving to the South, the WESTERLIES are not as much in play so Mid Latitude Storms can develop and get intense effecting areas where the exit sector of the Jetstream is or to the Southeast quadrant of the Jetstream is located. This area is where upper air divergence and surface convergence is greatest. The storm then follows the Jetstream and can effect a large part of the country. The Meridional flow is usually associated with a POSITIVE NORTH AMERICAN ANOMALY – this is where there is a DIP in the Jetstream in the East or what’s called a trough of low pressure(essentially a longwave trough) and a Ridge of High pressure in the West. The last 4-5 years this pattern has dominated North America and the United States. A NEGATIVE NORTH AMERICAN ANOMALY – Is where a Zonal pattern or flow is ongoing, or there is a dip in the Jetstream out West and a Ridge of High pressure in the Eastern 2/3rds of the country. Important note – If a Ridge of High Pressure is affecting your area in the Winter, warmer and drier conditions prevail. If a Trough of Low pressure is affecting your area in the Winter, it will likely be cooler and wetter or whiter depending on your location. I will depict an image of jetstreams to shoe temperature and precipitation differences.
This image shows the Meridional Jetstream pattern, or the Positive phase of the PNA. This image depicts stormy and cold in the East with the trough of Low Pressure and the Strong Ridge of High Pressure out West.
Remember when I said the positive PNA has been dominating the U.S. the last 4-5 years. Well what we see here is typical where we would see the Polar Jetstream from Winter and summer. In winter, it dives towards the gulf coast and turns up the east coast where I will be writing on how Lows affecting this region. And Summer it is located in the Northern tier of the U.S. and Southern Canada.
MID LATITUDE STORMS OF WINTER IN THE U.S.
1. LEE SIDE LOW PRESSURE SYSTEMS –
These Low pressure systems or cyclones form and intensify in the lee side(downwind) of the tall north-south facing Rocky mountain chain. These Lows form due to positive vorticity(counterclockwise) spin in the Lee side of the Rockies usually in Colorado. Westerly winds flow up and over the Rocky Mountains where air is compressed, warmed, and dried.(adibiatic warming). Air is compressed between the Mountain Crests and the Tropopause(part of the atmosphere). In the lee, the air column expands in the vertical(up and down), as it expands it generates POSITIVE VORTICITY and cyclonic flow. This cyclonic circulation is associated with positive vorticity, thus a trough of low pressure forms here and the jet stream responds with a DIP. In the Winter you will find many Lee-Side Lows just east of the Rockies, especially where peaks are tallest. Depending on where this Low travels or where the Jetstream develops determines what precipitation you will receive. If you are located on the North and Northwest you will most likely receive snow and a lot of it. If you are Northeast of the Low Pressure you will most likely start out with snow, and change to a mixed bag of precipitation – sleet and freezing rain. If you are south, or southeast of the Low Pressure you will likely receive rain or maybe severe weather as well. I will show you an image of a lee side Low to better emphasize my information.
This operational meteorology map shows the Lee Side Low forming in SE Colorado and transferring its energy to western Kansas. Precipitation in the form of rain has started south of the Low in Texas.
2. ALBERTA CLIPPER –
Alberta Clippers were named by colonists living in New England because the Clipper Boat was the fastest vessel back then, and Alberta Clippers just jetted on through at such a fast clip that is how they were named. ALBERTA CLIPPERS – are a cold-cored season storm that rapidly moves from East to Southeasterly direction. High Winds and Blizzard conditions usually prevail. Now with blizzard conditions you don’t need to have a great deal amount of snow. Visibility and temperatures are the main culprits which I will discuss in further detail later. Alberta Clippers usually bring high winds, cold temperatures but little snow because they are ‘moisture starved’. The Leeside low or Colorado Low bring heavier precipitation because they can tap into a moisture source like the Gulf of Mexico. The Alberta Clipper can bring heavier snow to New England, the Word CAN not will, due to the Atlantic Ocean, which is a large moisture source. Not all Alberta Clippers slow down enough to capture this moisture source. It all depends if the jetstream amplifies or dips far enough in a South – North pattern to create heavier snow.
This is a normal path of Alberta clippers in the fast trajectory east-southeast. You can see they are moisture starved until they get to Eastern New England. Tracks vary though some go further south bringing more snow to southern and central New England, and some go further North bringing heavier snow to Northern new England. Remember location is important to what precipitation you get. South of the Low in the winter mixed precipitation and North of the Low Snow likely.
3. PANHANDLE HOOKS –
This another cool to cold season Low Pressure system. The development and path of this Low Pressure is strictly contingent to the Upper Level trough or the JETSTREAM position. If mT or maritime tropical air is available from the Gulf of Mexico have snow and blizzard conditions can set up North and Northwest of the center of Low Pressure. Also with Panhandle Hooks severe thunderstorms can occur when mT(tropical) air clashes with cP(polar air). In fact the sinking of the Edmund Fitzgerald was due to a Panhandle Hook Low. Panhandle Hook Storms originate near the Oklahoma and Texas panhandles take a short SE trip and then jet straight North. This Low Pressure system is associated with the worst Great Lake Storms. Here is an image of all the storms I have written about.
The Red is an Alberta Clipper. The Blue and green are Colorado or Lee side Lows, and the Brown and yellow are panhandle hooks.( The yellow is a Gulf Low formed from a panhandle hook).
4. NOR’EASTERS –
I wanted to save my favorite for last. I grew up in Connecticut and I wish everyone could have experienced a Nor’easter in their lifetime. The Heavy snow, the wind and yes thunder and lightning with the snow. I know everyone remembers seeing Jim Cantore a meteorologist from the Weather Channel having numerous experiences in thundersnow, but so have I and its an AWESOME EXPERIENCE. Nor’easters can bring a variety of precipitation depending on the track of the storm, the intensity of the storm and the amount of cold air present for the storm.
4a. Nor’easters – are Mid latitude travelling Cyclones that travel up the east coast of the United States. I put the letter a because I am writing about how Nor’easters primarily form. Nor’easters bring strong wind in an Northeasterly direction – hence there name, heavy precipitation based on factors listed above, and sometimes hurricane force winds if the Low has “bombed out” or strengthen very rapidly. Meteorologists say deepen rapidly. Nor’easters develop or intensify rapidly offshore due to contrast in the cold continent of North America and the relatively warm Gulf Stream Current in the Atlantic Ocean off Cape Hatteras North Carolina. There is Cold air Damming off the continent and the warm waters thus Hatteras Low Formation. The following air masses are involved: cP/cA(Arctic or Polar Air) from the North and West, and mT and mP(maritime ocean Air) from the South and Southeast. Snow occurs from air mass mixing. In fact the Heaviest snows that occur along the I95 corridor occur when the Nor’easter tracks along a “40/70” Benchmark along the East Coast. 40=Latitide,70=Longitiude.
Important Note – If Low tracks to far out to sea, there is not enough moisture to produce heavy snow for the Mid-Atlantic and Northeast. And if the Nor’Easter tracks to far inland warm air is ushered into coastal communities due to the Low Pressures counterclockwise spin bringing maritime air in off the ocean.
4b. The b stands for Secondary Low forming off a primary Low pressure that is dying off to the West or transferring its energy to the east coast. The Primary Lows here are Lee Side Lows, Panhandle Hooks and Alberta Clippers that mature off to the West and then transfer their energy to the east coast near Hatteras or at times the DELMARVA Peninsula. These can become HUGE Nor’easters as well bringing feet of snow North of the Low formation, usually all of New England.
Several images of Nor’easters
This is a classic 40/70 Benchmark Nor’easter bringing feet of snow to southern and central New England. This storm is bringing in strong Polar winds from the Northeast coupled with Arctic Air in place and a strong moisture source the Atlantic Ocean. This means big time travel troubles, but skiers and snow lovers are rejoicing.
Remember what I mentioned the Secondary Low (Nor’easter) forming. Well here it is, classic snow track for Mid-Atlantic and Northeast.
5. BLIZZARDS –
The National Weather Service defines :
A. Blizzards – Wind Speeds greater than 35mph, and temperatures less than 20 degrees and snow hampering visibility under 500 feet. You don’t need a lot of snow to be called a blizzard. In fact it doesn’t need to be snowing at all if there is an existing snowpack being blown by 35+mph winds and temps lower than 20 degrees for at least 3 consecutive hours.
B Severe Blizzards – very rare, this occurs when winds are 45 mph or greater and temperatures are below 10 degrees, and visibility is less than 100 feet or pure whiteout conditions for at least 3 consecutive hours.
Blizzards are associated with strong Mid latitude Cyclones : Alberta Clippers, Lee Side Lows and even Nor’easters.
6. WINTER PRECIPITATION –
A. SNOW – When the column of air throughout the atmosphere profile is 32 degrees or less. Snow is beautiful six sided ice crystals that fall from cloud to ground.
B. SLEET– Sleet starts out as snow, but there is a layer in the atmosphere above 32 degrees, it is not thick its small, but it iss enough to melt the snow crystal to a drop of water, then the 32 degree layer is thick enough to freeze it into a ice pellet called sleet.
C. FREEZING RAIN – Freezing Rain starts out as snow high up by the cloud level, but the atmosphere below the clouds close to the surface is Above 32 degrees or the freezing point. So it melts to a drop of water until it reaches the surface or near the surface where temperatures are below 32 degrees. and freezes on contact. freezing rain is also called glaze because it coats roads, trees, and power lines. Freezing rain causes great disruption and destruction.
D. RAIN – Rain is an all 4 season precipitation type. Rain occurs when the entire atmosphere except at cloud level is above 32 degrees Fahrenheit. Rain is in the form of a water droplet. I will display an image of precipitation types to make everything clear.
Well that’s it. I hope everyone got a better understanding of winter type storms and precipitation associated with it. I had a fun time putting this together and I hope you have a great time reading it. Many Blessings from Brandon Brady.