June 29, 2021

Pacific Northwest Cools Off; Canada Breaks All-Time Heat Record For Third Day In A Row

Over the past day or so, we've had a tropical storm make landfall in South Carolina, flash flooding from heavy storms in Oklahoma, gross heat along the I-95 corridor, and a few more tropical systems possibly brewing far out in the Atlantic. Despite all that, the big story continues to be the heat that's plaguing the western United States and Canada.

Our neighbo(u)rs to the north claim the big headline again today with Lytton, British Columbia, securing the country's all-time highest temperature on record for a mind-boggling third day in a row.

Lytton, located about 60 miles northeast of Vancouver, recorded a high temperature on Tuesday of 121.1°F/49.5°C, once again setting Canada's all-time high temperature record.

The previous record, set on Monday, reached 118.2°F/47.9°C.

Monday's high temperature broke Sunday's all-time record of 115.9°F/46.6°C. 

Before this heat wave, the hottest air temperature ever recorded in Canada was 113°F/45°C, achieved during a heat wave in Saskatchewan in July 1937. 
Source: Google Earth

Lytton was the perfect spot (in a manner of speaking) to break this record three days in a row. The tiny town sits in a tight valley along the Fraser River that cuts longitudinally through the heart of British Columbia. Lytton's low-lying location makes it an effective heat sink during a record-shattering heat wave.

It's been historically putrid across the Pacific Northwest. The anomalies were so great that some meteorologists speculated last week that the models were broken for showing high temperatures soaring past the all-time highs in cities like Seattle and Portland.

The not-so-funny thing about extreme weather is that we have little frame of reference for events like the one winding down in the Northwest. We had no reason to believe the models showing highs climb so high above the previous records because that sort of thing is such a rarity.

It sure did happen.

Portland blew past its previous hottest temperature record by 9°F—topping its own record three days in a row. Salem, Oregon, set its new record by the same margin. The Dalles, Oregon, where readings are taken a few miles away in Dallesport, Washington, broke its all-time high by 7°F. Seattle broke its all-time high temperature by 5°F.

Most all-time high temperature records are tied or toppled by just a degree or two. This kind of heat was unimaginable just a week ago. And it's taken its toll.

It'll probably be a while before we get a full idea of how many people were injured or killed by the heat. Preliminary reports indicate that dozens of sudden deaths were attributable to the heat up in British Columbia. Extreme heat waves in Europe, where many homes also don't have air conditioning, have claimed hundreds of lives in recent decades. Chicago's extreme heat wave in July 1995 killed more than 700 people.

As for the heat wave itself, the worst is over along the I-5 corridor. The ridge began to weaken and move inland on Tuesday, allowing the marine layer to reassert control over coastal communities in Washington, Oregon, and British Columbia. Tuesday's high temperatures "only" made it to 84°F in Seattle and 93°F in Portland—still above normal and it still felt miserable with the humidity, but it was a far cry from what they've seen over the last few days.

Hot weather will continue in eastern Washington and the Intermountain West for the remainder of the week, however, as the ridge parks itself over the northern Rockies and Plains/Prairies. Temperatures in the upper 90s to low 100s will spread over the northern Plains and Canadian Prairies through the weekend before the ridge finally starts to subside and the pattern starts moving along again.

There's no rain to speak of in the Weather Prediction Center's 7-day forecast, which is terrible news for wildfire prospects over the next week. Several large fires have already broken out in British Columbia and northern California (the smoke each can be seen in the satellite image at the top of this post). The extreme heat dried out the already-parched vegetation across the region, and continued warm and dry conditions could allow further fires to spark and spread with relative ease.

[Top Image: NOAA]

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June 27, 2021

Canada Shatters All-Time Temperature Record; Same Records Fall In Seattle And Portland

Canada's all-time high temperature record fell on Sunday. The previous record high of 45°C, set in Saskatchewan in July 1937, shattered in style on Sunday afternoon when the observing station in Lytton, British Columbia, spiked to 115.9°F, or 46.6°C to be Canadianly correct. It's possible that the record could be broken or matched again on Monday, and maybe even again on Tuesday. Whew.
The superlatives-aren't-enough-to-describe-it heat wave roasting the Pacific Northwest and southwestern Canada is an event that meteorology students will use as a case study for generations to come. It's just not supposed to get this hot in this part of the world.

An extreme ridge of high pressure, combined with downsloping winds limiting the marine layer to the immediate coastline, are pushing temperatures to levels we've never reliably recorded before.

The National Weather Service's forecast for the airport in Portland, Oregon, on June 27, 2021.

The official reporting station at the airport in Portland, Oregon, saw a high temperature of 108°F on Saturday, breaking the city's all-time high temperature record. Portland broke the record again on Sunday with a preliminary high temperature of 112°F.

It's likely that Portland will break the all-time record for a third day in a row on Monday, with a predicted high of 115°F, a breathtaking forecast that's only two degrees lower than the hottest temperature ever measured in Las Vegas, Nevada.

The National Weather Service's forecast for the airport in Seattle, Washington, on June 27, 2021.

Seattle, Washington, had only recorded three days with a high temperature of 100°F or hotter until this event. Saturday's high of 102°F made the fourth, Sunday's all-time hottest high of 104°F made for five, and they're on track to see their sixth—an unbelievable predicted high of 110°F—on Monday afternoon, doubling their total number of triple-digit heat days in just one long weekend.

Many other communities not named Portland and Seattle broke their all-time high temperature records, as well, including Olympia WA (105°F), Port Angeles WA (97°F), Salem OR (112°F), and Eugene OR (110°F).

And then there's British Columbia.

Canada just doesn't get that hot. It's far to the north, sure, but its wintry image for those of us south of the border masks the true diversity of the country's climates and scenery. It gets hot on the Prairies, supremely gross and sticky in southern Ontario, and it can pretty darn hot in the valleys of southern British Columbia. You can easily see those valleys on the map at the top of this post, lacing through British Columbia like white hot veins.

Lytton, located about a hundred miles northeast of Vancouver, is one of those communities that's situated at the bottom of a valley, the perfect spot to feel the burn of a record-setting heat wave. There are a couple of similarly situated communities that could easily match or topple this newfound record in the coming days, including Abbotsford (southeast of Vancouver), Osoyoos (near the Washington border in south-central B.C.), and Kamloops (about 60 miles northeast of Lytton).

This is a public health emergency for the affected areas. Lots and lots of people are going to fall ill or even die because they can't properly cool off from day after day of record-smashing temperatures. Many homes in this part of the country do not have air conditioning, and residents are certainly not acclimated to desert-like heat. The flip-side comparison might be if Miami, Florida, were to fall below 0°F for three days straight, but even then, it's easier to warm up than it is to cool off.

The first day of winter is only 177 days away.

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June 25, 2021

An Unprecedented Heat Wave Will Grip The Pacific Northwest Through Next Week

The growing heat wave in the Pacific Northwest could be the worst in living memory as predicted highs would shatter all-time temperature records across the region. This part of the country is not equipped to handle a long-duration extreme heat event like this. Daytime high temperatures will soar well above 100°F in many areas, scorching communities where most homes do not have air conditioning. Please treat this heat wave as the weather emergency it is. It's no joke.

All-Time Temperature Records Might Fall

I combed through xmACIS2—a fantastic resource if you're looking for historical weather data—and put together a map of all-time record high temperatures across the areas expecting extreme heat.

  • The hottest temperature on record in Seattle, Washington, was a 103°F reading on July 29, 2009.

  • The hottest temperature on record in Portland, Oregon, was 107°F, a temperature the site has achieved on three separate days since 1938. The most recent 107°F reading was on August 10, 1981.

  • The hottest temperature on record in Spokane, Washington, was 108°F, most recently set on August 4, 1961—to put that in perspective, that's the day Barack Obama was born.

  • The hottest temperature on record in Yakima, Washington, was 110°F, achieved on August 10, 1971.
All four of those all-time highs could fall in the coming days, and it's a similar story in smaller communities around the region.

Extreme heat is likely across the border in British Columbia, as well, where Canada's all-time high temperature record of 45°C/113°F is at risk of toppling (again, that's the hottest temperature on record for the entire country).

Predicted Highs

Here are some predicted high temperatures from the National Weather Service:

It's easy to see that we have two concurrent stories here, including that

1) this is a historic heat wave, and

2) the heat wave is going to last much longer inland (Spokane and Boise) than it will closer to the coast (Seattle and Portland).

Here's a loop of the NWS's predicted high temperatures between Saturday, June 26, and Friday, July 2:

The animation does a pretty good job highlighting how the heat will creep away from the coast after this weekend and park itself inland through the balance of next week. Eastern Washington will be hotter than the desert Southwest for a couple of days. There's a decent chance we're still talking about the unrelenting heat around this time next week. For reference, the longest streak of 100°+ days on record in Spokane was six days in July 1928, and they're well positioned to blow past that record.

(If you're curious, see the note at the bottom of this post for why the temperatures on my map don't line up perfectly with the chart above.)

Why It's So Hot

SourceTropical Tidbits

A significant ridge of high pressure is building over the western United States and Canada today. The ridge is pinched between two troughs that are serving to block the ridge from simply fading away in a day or two. This pattern will force the ridge to sit and intensify, forcing the heat to build on itself for days at a time.

Air sinks beneath ridges. This sinking air compresses as it descends toward the ground, causing the air to heat up and dry out as it approaches the surface. Clear skies will allow the bright early summer sunshine to heat both the atmosphere and the ground, leading to extreme temperatures for as long as the ridge remains in place.

The drought isn't helping matters much, either. As I explained during last week's heat wave, one reason it usually doesn't get this blazingly hot outside of the deserts is that high soil moisture acts like a thermostat that regulates air temperatures. Since water heats up more slowly than air, humidity added to the air by moist soil prevents temperatures from climbing as high as they could on a dreadful summer day.

Take away that soil moisture and you've removed a key regulator on the air temperature. Not only that, but the parched soils will be able to absorb and release more heat into the air, allowing temperatures to grow hotter than they would under "normal" conditions.

Source: NOAA

Climate change is an undeniable factor in this latest episode of an unrelenting barrage of heat waves in recent years. Global temperatures have steadily risen over the past century and that uptick has accelerated in recent decades.

NOAA's new climate averages, the 30-year period between 1991 and 2020 that will serve as our frame of reference for "normal weather" over the next ten years, showed that average temperatures have risen across almost the entire United States. This higher temperature baseline, combined with more frequent weather extremes, will provide the opportunity for more precedent-busting heat waves like the one we're staring down this weekend.

Please Take It Easy

It's common for people in warmer climates to scoff at hot weather in northern or coastal climates. "It's only going up to 105°F in Seattle? Gee, you should visit Macon sometime! Our heat index is 105°F all summer. Ha!"

Extreme heat is a matter of what you're used to and what you're equipped to handle. Most homes in the Pacific Northwest don't have air conditioning. Only about 41 percent of homes in the Seattle metro area are air conditioned. Try going through 100-degree heat for days on end without any relief at night and no cooling in your house. Not even a southerner would be able to tolerate that for very long, let alone folks who live in a cooler climate.

Humidity makes the south's heat feel awful, of course, because your body relies on sweat to stay cool. You sweat, the sweat evaporates, the evaporation cools your skin, and your body temperature comes down. High moisture in the air disrupts that process and keeps your sweat from evaporating, preventing you from cooling off properly.

That's why we have the heat index to tell us how the combination of heat and humidity affects our body the same way a higher temperature would. A heat index of 105°F means your body has to work as hard as it would if the actual air temperature were 105°F.

The actual air temperature during this heat wave in the Pacific Northwest will be as hot as the heat index on a gross summer day in the south. The only difference is that it's worse for the Seattleite because they're not used to it and they have limited options to cool down.

Heat Is Deadly


This is the kind of heat wave that could take an awful toll on vulnerable communities such as the elderly, folks who are low-income, and those who suffer from medical conditions that make them more susceptible to heat-related illnesses. There are probably going to be healthy folks who die because of overexertion. It doesn't matter how fit you are or how young you are, the heat can take a toll and its effects can set in quickly. Similar heat waves in Europe, where home air conditioning is rare, have claimed hundreds of lives.

The intensity of an extended heat wave compounds on itself the longer the event drags on. One day's heat settles into a putrid night. Homes won't have the opportunity to cool off much at night, either. It's not out of the question that the air temperature in homes and apartments could reach 90°F or hotter after a few days. This is going to be really rough on a lot of people.

Don't fool around with the heat. If you don't have air conditioning, try to access an air conditioned space several times a day so you have a chance to cool off and recover. Keep fans on and circulate the air as much as possible if you don't have air conditioning at home. Moving air is better than nothing at all. Drink lots of water, too—it seems silly to say that to adults, but dehydration sets in fast and it can sneak up on you.

Behind The Scenes Note

I make my temperature maps using data from the National Weather Service. The NWS issues most of its forecast products on a grid made up of boxes that each cover 2.5 square kilometers of land. There are more than a million of these boxes covering the United States.

I tell my mapping software to select a handful of these grids to represent temperatures in major cities such as Seattle and Portland. The box I select for my maps isn't always the box you'll land on if you use the NWS website's point-and-click forecast. The temperatures I pulled for my chart in this post are for the major airport in each city—Seattle-Tacoma Airport, the city's official observing station, is many miles away from downtown Seattle, so the temperatures don't exactly line up.

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June 21, 2021

Claudette Strengthened Into A Tropical Storm Over Land—Twice

Claudette regained its tropical storm status over North Carolina on Monday as the system picked up speed and touched ocean water for the first time as a named storm. This is the second time that Claudette reached the all-important (yet arbitrary) threshold of becoming a tropical storm, and both times it reached that milestone while the center of circulation was over land. That's not unheard of, but it is a little odd. Here's how it happened.

Claudette's Journey

This storm spent its first couple of days of existence as a "Potential Tropical Cyclone," a bureaucratic title that allows the National Hurricane Center to issue watches and warnings for a disturbance that's expected to develop into a tropical storm and hit land within the next 48 hours.

Before this special designation, forecasters had to wait until a system was officially a tropical cyclone to issue watches and warnings. There have been instances where this didn't happen until just a few hours before landfall, in which case the warnings were all but useless.

The disturbance existed as a broad low-pressure system as it traversed the northern Gulf of Mexico during the day on Friday. Upper-level wind shear kept its thunderstorms far removed from the center of the system. This asymmetry is why Alabama and Florida received the bulk of the flooding rains and tornadoes on Friday and Saturday.

Word came in Saturday's 5:00 AM advisory that the disturbance had met the criteria necessary to become Tropical Storm Claudette. Its center of circulation was just over southern Louisiana by that point, sitting over swampy land southwest of New Orleans. 

Claudette quickly weakened into a tropical depression as it traversed the southeastern United States, restrengthening into a tropical storm as its center passed near Fayetteville, North Carolina. The system picked up speed as finally entered open waters, and it's expected to lose its tropical characteristics as it heads toward Atlantic Canada.

Lows Don't Fit Your Silly Labels

This was a weird storm. But you know what? Some storms are just weird.

Lows, or cyclones, exist on a spectrum with extratropical cyclones on one end and tropical cyclones occupying the opposite end.
A large extratropical cyclone swirls over the northern Atlantic in March 2020. (Source: NOAA)
An extratropical cyclone is the "everyday" type of low-pressure system featuring fronts that can herald big swings in temperature and humidity as they pass through. These systems are driven by diverging winds in the upper levels of the atmosphere, which draw air up and away from the surface to create the center of low pressure.
Hurricane Joaquin in 2015 (Source: NOAA)
A tropical cyclone is a low-pressure system that's warm and humid throughout the storm (in other words, no fronts). Tropical cyclones are powered by thunderstorms around the center of circulation, which derive their energy from warm ocean waters. As the thunderstorms grow more powerful, their updrafts pull more air away from the surface, deepening the pressure at the center of the low, which intensifies the storm and continues the cycle.

Lows don't always fit into the "extratropical" or "tropical" boxes. There's a whole array of hybrid cyclones that can exist somewhere in the murky middle between the two types of cyclones.

Some of these hybrid systems are called subtropical cyclones, which receive names and full forecast packages from the National Hurricane Center because they're similar in structure and impact to tropical cyclones.

Others are...debatable. Hurricane Sandy is an infamous example of a system that straddled the line between tropical and extratropical as it approached landfall in New Jersey. Sandy officially lost its title as a hurricane at the moment of landfall, which turned out to have huge implications for insurance companies.

Claudette the Land-Dweller

Claudette is another fine case study in nebulous low-pressure systems that are tough to categorize.  The system's structure, surface wind circulation, and thunderstorm placement precluded the experts from calling it a tropical depression or tropical storm for most of its journey through the northern Gulf of Mexico. Forecasters observing the storm say it didn't meet that threshold until its center had just crossed the coastline. 

Technically, this tropical storm existed entirely over land for 48 hours, and only touched warm ocean waters for the first time on Monday afternoon when it scooted over North Carolina's Outer Banks into the western Atlantic Ocean.

It's possible for tropical cyclones to form and strengthen while their center is over land. Tropical cyclones are more than just the pinpoint at the very center of the system. Claudette spanned more than a hundred miles across over the northern Gulf Coast, consisting of thunderstorms that were both near and far from the center of the storm.

The disturbance became a tropical storm when its center was just over the Louisiana coastline. This area is swamp. It's barely land to begin with, really, and it's not a stretch for a storm to take advantage of swamps to maintain strength or intensify.

We've seen storms form or strengthen over the Florida Everglades, for instance, and one storm (Tropical Storm Julia in 2016) was declared a tropical storm while its center was over land in northeastern Florida. 

There are also plenty of documented cases of tropical cyclones maintaining composition and strength after they make landfall. The "brown ocean effect" describes the phenomenon when warm and moist soils can act like warm ocean waters that help sustain a tropical cyclone while it's over land.

What made Claudette a tropical storm over Louisiana? Well, the National Hurricane Center's forecast discussion early Saturday morning was...vague:
The system that we have been tracking for a few days finally has enough of a well-defined center and organized convection to be considered a tropical storm. While the organization is not classical by any means, and there are some hybrid characteristics, the cyclone most resembles a sheared tropical storm, so the system is now Tropical Storm Claudette.
I'm willing to bet they were short on technical details on purpose due to the subjectivity of a call like that. It would've been great to have a seat on the operations floor to listen to the discussion surrounding that call.

Forecasters issued a beefier discussion for Claudette's second upgrade to tropical storm status while its center was over eastern North Carolina on Monday morning:
The elongated low-level center of Claudette is located over eastern North Carolina this morning, while a curved band of convection continues pushing eastward across the adjacent coastal and offshore waters. Surface pressures have fallen slightly overnight near the estimated center position, and Frying Pan Shoals buoy 41013 off the coast of southeastern North Carolina reported a brief period of sustained tropical-storm-force winds shortly after 06 UTC. Therefore, Claudette's initial intensity is raised to 35 kt with this advisory, making it a tropical storm once again.
This probably isn't going to be the last oddball storm we see this year. There are always systems that walk a fine line between a sad sack of clouds and a formidable cyclone.

It's all about the impacts, anyway. Claudette was physically unimpressive but its heavy rains wreaked havoc on parts of the northern Gulf Coast. Names and classifications are largely arbitrary, especially when there's a foot of rain or a storm surge on the way.

[Top Image: NOAA]

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June 14, 2021

Phoenix Could See One Of Its Hottest Streaks On Record As Extreme Heat Builds Across West

A significant heat wave will build across much of the western United States this week, bringing record-threatening temperatures to a region that could stand a break from the relentless warmth and dryness. Excessive heat warnings in place for communities like Phoenix, Arizona, which could be on the cusp of one of their hottest stretches ever recorded. 

The Setup

Source: Tropical Tidbits

A steep upper-level ridge will build over the western United States and Canada, allowing strong high pressure to dominate the region's weather through next week. Air sinks beneath a ridge, warming up and drying out as it falls toward the surface. This pattern will allow the hot summer sun to push afternoon temperatures toward the top of the records, especially in the Southwest. 

The ridge will grow strongest by mid-week—potentially leading to triple-digit high temperatures as far north as the Canadian Prairies—before beginning to weaken later in the week.

The animation above (from Tropical Tidbits) shows the upper-level ridge on the Monday morning run of the GFS model. The map depicts the 500 millibar level of the atmosphere, which is usually around 20,000 to 25,000 feet above sea level, giving us a great view of the ridge over the west.

The Heat

Beginning on Monday, forecasters expect the high temperature in Phoenix, Arizona, to push 115°F and hit or exceed that mark every day through Friday. Triple-digit readings are likely in and around Las Vegas, Nevada, during the same period, while the interior suburbs of Los Angeles and San Diego could push 100°F for several days during the first half of next week. Highs could peak near 110°F in California's Central Valley toward the end of the week. Record-breaking heat will even stretch as far north as Utah and western Colorado.

An excessive heat warning is already in effect for a significant portion of the Southwest for the next week, while a slate of heat alerts will progressively cover more communities across the western United States in the coming days.

It's a "dry heat," of course, but that doesn't matter much when temperatures are this darn hot. The low temperature in Phoenix will sit close to 90°F for a couple of days this week. When it's in the upper 110s during the day and near 90 at night, you're not cooling off that much!

The heat index tells you what the outdoor temperature feels like to your body when you factor in the humidity. (Humid air prevents sweat from evaporating, which limits your ability to cool off efficiently.) If it's 90°F with a heat index of 105°F, the heat is hitting your body as hard as an actual air temperature of 105°F even though it's much cooler.

The actual air temperature in much of the west is going to be hotter than the highest heat index you'll ever encounter in the southeast or central states.

This is a brutal, uncompromising heat that's tough for anyone to handle. The healthiest, most summer-hardy person is liable to fall out if they're not careful in these temperatures. This is going to be an awful stretch of weather for anyone who can't get relief from the elements, especially folks who are low-income, elderly, work outdoors, or those who live with illnesses that make heat tough to handle.

The Records

Extreme heat itself isn't rare in the Southwest. Phoenix, Arizona, has recorded a high temperature of 115°F at least once in 15 of the last 16 years, while temperatures of 110°F or greater are a yearly occurrence in Las Vegas, Nevada. 

What is unusual, however, is the timing and duration of this heat wave. It's early in the season for such hot temperatures in the Southwest. Phoenix doesn't typically record its first 115°F reading until the first week of July, while the end of June marks the average first appearance of a high temperature of 110°F in Las Vegas.

The duration is also what's really going to take a toll. Phoenix's longest streak of days with a high temperature at or above 115°F was 4 days. The NWS's current forecast calls for five days of afternoons hitting that mark, every day from Monday through Friday, which would make this the hottest stretch the city's recorded in living memory in terms of afternoon highs.

The Drought

Extreme heat baking areas experiencing an extreme drought is terrible news for folks who live in fire-prone areas. Last week's update of the U.S. Drought Monitor found that week-over-week drought conditions stayed the same or worsened west of the Rockies, and that's probably going to be the story over the next few months as hot temperatures and little rain exacerbate damage to the parched land.

The combination of widespread drought and persistent above-average temperatures has experts terribly worried about this year's wildfire season in the western states. Fire activity is already above-average for this point in the year and the region still has a long, hot stretch to get through before hoping for beneficial rainfall from the Southwest's midsummer monsoon and California's wet season in the fall.

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June 6, 2021

Intense Heat Wave Shatters Records In Rarely-Roasted Parts Of U.S. And Canada

An intense heat wave that's swept over the United States and Canada over the last week will hear its last hurrah in New England and the Canadian Maritimes on Monday before temperatures cool down to a more manageable level. The heat set impressive temperature records from California to Manitoba, generating more heat than some communities have seen in a generation.

A strong upper-level ridge formed over the eastern Pacific early last week, bringing unseasonably hot temperatures to the West Coast. The high temperature in Sacramento, California, reached 105°F on Monday, May 31, the second-earliest instance of such a hot reading in the state capital. (The earliest temperature of 105°F or hotter in Sacramento occurred on May 28, 1984.)

Temperatures didn't get any cooler as the ridge crested the Rocky Mountains. The pattern allowed high temperatures to break the century mark as far north as Manitoba, which saw some of its hottest readings in decades.

Friday, June 4, saw a scorching high temperature of 106°F in North Dakota's capital of Bismarck, while Grand Forks, North Dakota, saw its first triple-digit reading since 1989. High heat continued moving east with the ridge, with temperatures well into the 90s across parts of Maine and eastern Canada.

It's not easy to get this much heat this early in the season. A strong upper-level ridge allowed the heat to crank as the feature crossed the United States and Canada. Weather conditions beneath an upper-level ridge are usually calm and warmer-than-normal because ridges foster sinking air, which heats up and dries out as it descends toward the surface. Southerly winds reinforced the warmth.

The powerful upper-level ridge had assistance from the drought plaguing the northern Plains and Canadian Prairies. The latest update of the U.S. Drought Monitor found extreme to exceptional drought covering much of the northern U.S. and south-central Canada.

Soil moisture and vibrant vegetation both add humidity to the air, which typically helps to modulate temperatures in agricultural communities during the heat of the summer. (Think about how humid it gets in places like Iowa and Illinois when the corn is in season.) Lacking that additional moisture, temperatures were able to climb far higher than normal, breaking longstanding records in many locations.

It'll be another hot day on Monday with high temperatures approaching the upper 90s in parts of New England and eastern Canada. The NWS's forecast on Sunday night called for a high of 98°F in Manchester, New Hampshire, on Monday afternoon, while highs could top out in the 90s on Prince Edward Island, where a heat warning is in effect. Temperatures will return closer to normal as the week wears on.

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June 3, 2021

It's Hurricane Season. (Again.) Here's What To Expect Heading Into The Summer Months.

Well...here we are. Even though the de facto beginning of the Atlantic hurricane season came on May 15, and we’ve seen our first named storm already, this week is still the official start of the season on paper. Forecasters expect above-average activity in the Atlantic Ocean this year. While we probably won’t come close to matching last year’s all-time record of 30 named storms, even one storm is bad news if it hits land.

The Forecasts

An average Atlantic hurricane season produces 14 named storms, about half of which become hurricanes and a few of those strengthen into major hurricanes. This 30-year average includes both hyperactive years (2005 and 2020) and relatively quiet years (2014 and 2015) alike.

Forecasters (see CSU and NOAA for examples) generally expect an above-average hurricane season this year. These forecasts are based on a variety of trends in long-range models, including water temperatures in the eastern Pacific, water temperatures in the Atlantic, and other factors like overall wind and pressure patterns.

One annoying feature of these long-range forecasts is that they predict a specific number of storms. Ignore the numbers. There’s not much anyone can do to alter their hurricane preparedness based on whether we’re expecting 14 named storms or 17 named storms. Even one storm poses a grave threat to safety and property if it approaches land.

The Niño

El Niño and La Niña get huge billing at the beginning of a hurricane season. There’s lots of talk about it, but little talk about why it’s important.

It seems counterintuitive, but water temperatures in the eastern Pacific matter for storms over in the Atlantic because of the El Niño-Southern Oscillation (ENSO), which produces El Niño and La Niña events. El Niño describes warmer-than-normal waters in the eastern Pacific, while those same waters are colder-than-normal during a La Niña.

These temperature anomalies can affect weather patterns over the region, which in turn influences the potential for tropical development over the Atlantic Ocean. El Niño events often lead to destructive wind shear flowing over the Atlantic that nips developing tropical cyclones in the bud, while La Niña events can suppress wind shear and remove a major obstacle to tropical development in the Atlantic.

The latest projection from the Climate Prediction Center calls for ENSO-neutral conditions to persist through the summer months, with water temperatures right around normal for this time of year and neither El Niño nor La Niña present. The Atlantic tends to see healthy tropical development during ENSO-neutral conditions, so that factors into the forecasts.


The National Hurricane Center’s website should be one of your first visits in the morning if you live anywhere near the coast. (Let’s be honest...if you’re reading this, it probably already is. Good on you.)

Hurricanes.gov is responsible for providing information about tropical cyclones in the Atlantic, the eastern Pacific, and the central Pacific basins, which covers everyone from Hawaii to Portugal.

The agency issues daily tropical weather outlooks at 2:00 AM/PM and 8:00 AM/PM Eastern every day between May 15 and November 30. Tropical weather outlooks cover potential tropical development over the next five days, with the option for more additional updates as needed. These should be required reading during the summer and fall months.

Once the NHC initiates advisories (forecasts) on a storm, forecasters will release new advisories at 5:00 AM/PM and 11:00 AM/PM Eastern for the duration of the system. If there are any watches or warnings in effect for land, they’ll issue intermediate advisories in between full advisories, giving us updates on the storm every three hours. (All times are an hour earlier once we set the clocks back in the fall.)

Each full advisory offers plenty of written and graphical information about storms, including:
  • A three-day and five-day forecast map for the storm’s path and intensity
  • Watches and warnings for land near the storm’s path
  • The current extent of tropical storm force/hurricane force winds
  • The estimated and likely arrival times of tropical storm/hurricane force winds
  • Wind speed probabilities for locations along the storm’s predicted path
  • Storm surge forecasts for coastal areas in the United States

The Cone

The single most important product to understand is the cone of uncertainty.

The cone of uncertainty is the historical margin of error in the National Hurricane Center’s forecast track. The center of the storm stays within the cone of uncertainty about 66 percent of the time, which means it tracks outside of the cone the remaining one-third of the time.

It’s so important to understand the cone of uncertainty because it gives us a clue of where the storm could travel based on errors made in past hurricane forecasts. Forecasters calculate the extent of the cone using forecast errors from the previous five years, so 2021’s forecast errors include the 2016-2020 hurricane seasons.

The cone is actually a radius drawn around each of the eight timesteps in the forecast period—12 hours, 24 hours, 36 hours, 48 hours, 60 hours, 72 hours, 96 hours, and 120 hours.

The error is smaller at 12 hours than it is at 48 hours, and the error smaller at 48 hours than it is at 120 hours. This year, the error at 12 hours is 31 miles while the error at 120 hours is 230 miles. All of these circles get smoothed out and joined together so they create one cone that’s narrow at the beginning of the forecast and large at the end of the forecast, visualizing the potential for error in the track forecast.

Even though the cone looks pudgy on some forecasts and super narrow in others, the margin of error always remains the same throughout the season. The shape of the cone depends on the speed and shape of the forecast track. A slower forward speed or a curvy track will result in a shorter and thicker cone because the error circles around each timestep overlap with one another.

Some forecasts are easier to nail than others. Last year’s Hurricane Laura is a great example of a storm that falls on both ends of the spectrum. The storm’s forecast track was tough to pin down early in its existence when it was weak and there were lots of factors pushing and pulling on the storm, but the NHC's forecast came within a few miles of its landfall point in southwestern Louisiana within more than three days before the category four hurricane moved ashore.

The Names

Names are the most important non-issue when it comes to a tropical storm or hurricane. The system of naming hurricanes is occasionally cumbersome or controversial, especially when an unnamed tropical disturbance causes major flooding but it’s still too disorganized to earn a name. 

This year’s list of names was last used in 2015. The World Meteorological Organization retired the names Erika and Joaquin after that season due to the damage caused by those storms, replacing them with Elsa and Julian on this year's list.

Names became a big deal last year because the Atlantic hurricane season produced so many storms that we exhausted the official list of 21 names, requiring the use of the Greek alphabet to name the final nine storms. The resulting confusion and need to retire two of the names (Eta and Iota) forced the WMO to ditch using the Greek alphabet as a fallback.

Beginning this year, in the unlikely event that this or any future season exhausts its list of names, we have supplementary name lists for both the Atlantic and eastern Pacific basins ready to serve as a fallback. These names should cause less confusion going forward and they’re easier to replace if needed.

The Prep

Hurricanes don’t really sneak up on us anymore. If there’s a bad storm heading for land, we usually get a couple of days to prepare before it arrives. That gives folks in harm’s way plenty of time to hit all the checkmarks on the to-do list, like filling up the gas tank and getting ready to leave if told to do so.

You have to wait until the storm is on its way to do the disruptive last-minute prep. There’s plenty you can do now to make things easier if and when the time comes to take action.

Keep a reserve of non-perishable food on hand in case the power goes out. This isn’t just helpful for hurricanes, but it's useful for any summertime storm that could knock out the power. It’s easy to forget how much we rely on electricity for food until the electricity turns off. Stuff like canned foods, Pop Tarts, and fruit cups are easy to store, fine to eat cold, and they have a long shelf life.

Make sure you have batteries and flashlights. The flashlight feature on cell phones is fine in a pinch, but it’s not there to get you through a power outage. That bright light kills your cell phone battery in a hurry. Have a couple of real flashlights (and battery refills) on hand so you don’t have to worry about draining your phone’s juice or burning unsafe candles during a lengthy outage.

Speaking of cell phones, invest in one (or more) cell phone battery charging packs. They’re relatively cheap nowadays and they’re good for a couple of recharges before the charging pack itself has to be recharged.

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