By Steve Elliott / ADOT Communications

So what does ADOT have against traveling to play in the snow?

Nothing, actually. We enjoy throwing snowballs, sledding, etc., as much as anyone. Being able to enjoy mild winters in our deserts and then be playing in the snow in just a few hours is one of the things that makes Arizona so special.

Then why, you may wonder, has ADOT spent so much time of late telling you what NOT to do when you're heading uphill for some winter fun?

Like when we warned against parking on highway shoulders to play in the snow. Or told you that holiday traffic can be heavy around popular snow-play areas, particularly along US 180 outside Flagstaff? Or posted a Facebook video telling you to not pass a snowplow, among other tips? Or warned you that too many people leave for the high country without emergency kits or even proper footwear?

It's simple: We want you to leave prepared and make smart decisions when you reach your winter wonderland of choice, whether that's the Flagstaff area, Mogollon Rim, White Mountains, Prescott or Mount Lemmon. That's part of wanting you to have fun.

With snow in the forecast for Christmas Eve and many people on vacation through New Year's weekend, there's a good chance you're thinking about heading for snow country.

If you do, have a great time. Seriously. Just Know Snow before you go. And be patient: Depending on the severity of the coming storm, it may take our plows some time to get snow and ice off the roads.

Please keep an eye on az511.gov and our Facebook (facebook.com/AZDOT) and Twitter (@ArizonaDOT) accounts for the latest highway conditions. You also can call 511.

We can't resist ending with one last piece of advice: When throwing snowballs (after dressing appropriately, driving safely, parking off the highway, etc.), you'll have more success if you aim for your opponent's center of gravity.

By Ray Greely / ADOT Meteorology Intern

Now that the monsoon has come and gone and fall-like weather is upon us, we look toward the winter season and the outlook for severe weather.

Last winter, a powerhouse El Nino pattern was expected to bring well-above-normal precipitation but instead brought mostly drier conditions to the state. The Pacific Northwest wound up receiving much of the precipitation as a persistent ridge of high pressure over the Southwest kept the storm track north of us.

We are currently in a mild La Nina pattern, but this may shift into what forecasters call a neutral phase.

Let’s review the winter outlook from the following sources: NOAA Climate Prediction Center, Old Farmer’s Almanac and The Farmer’s Almanac.

Sea surface temperature anomalies

Figure 1 (Top) - Pacific sea surface temperature anomalies for October 1st 2015. Notice the strong El Nino area within the encircled region. Last winter, arizona was drier than expected despite the presence of a strong El Nino. Source: NOAA-National Environmental Satellite Data and Information Services

 

Figure 2 (bottom) - pacific sea surface temperature anomalies for October 3rd 2016. Notice the weak La Nina area within the encircled region. Source: NOAA-National Environmental Satellite Data and Information Services

NOAA Climate Prediction Center

The Climate Prediction Center’s forecast is based on climatology trends, oceanography and computer model output from October 2016 through March 2017. This time period is broken into two three-month forecasts, the first running from October through December and the second from January through March.

At present, there is a 73-83 percent chance that temperatures will average above normal for fall and winter. Precipitation is expected to remain near the norm from October through December and then slide to below normal from January through March.

The probability of below-normal precipitation is between 66-73 percent, with the driest conditions expected in southeastern Arizona. This suggests that once winter settles in, high pressure will dominate our weather and keep the storm track to our north.

Temperature Forcasts

Old Farmer’s Almanac

The Old Farmer’s Almanac doesn't share the sources of its forecasts, but the results are nonetheless entertaining. Last year, its forecast for Arizona called for a drier-than-normal winter. With the exception of January, that was a fair assessment for most of the state. The almanac forecasts mild, dry conditions for Arizona this year.

Farmer’s Almanac

A competitor to the Old Farmer’s Almanac, the Farmer’s Almanac, places Arizona in a "balmy and wet" zone this winter, which seems strange when nearly the same weather is forecast for the Pacific Northwest. Typically, if we experience a wet winter then the Pacific Northwest will see normal to drier conditions. But anything is possible.

So two out of three sources are calling for above-normal temperatures and mostly below-normal precipitation. Keep in mind that these are outlooks take an average over an entire season, and while these long range outlooks can give us a general idea of what the winter conditions may be, they don't account for any short-term anomalies. For instance, a forecast of a mild and dry winter doesn't mean that the entire winter will be this way. Extreme weather can still occur and could wind up being more dangerous if people aren't prepared for it.

Whatever the weather brings this winter, make sure you're prepared by following our winter travel tips. 

Editor's Note: ASU’s School of Geographical Sciences & Urban Planning has partnered with ADOT to place graduate-level meteorology students in the ADOT Traffic Operations Center. This allows ADOT to have better information about weather conditions and more quickly determine how to deploy crews and communicate with the public.

By Ray Greely / ADOT Meteorology Intern

Monsoon rains are forecast to return to Arizona on Tuesday. Strong winds, blowing dust, heavy rain and lightning often accompany these storms from June through September.

Have you ever wondered what climatological features are responsible for these seasonal thunderstorms or why these storms often move from the east to west? We'll explain that and look at the reason why Tropical Storm Javier may bring heavy rain to the state this week.

The monsoon high pressure system

One critical ingredient to the Arizona monsoon is the sub-tropical or monsoon high that's part of a high-pressure belt forming along the northern flank of the tropics. During the winter and spring, this belt moves well south of Arizona, allowing for a westerly steering current to control Arizona’s weather. In the summer, it shifts north. This weakens and can even reverse the westerly flow depending on where it positions itself in relation to the state.

Winds flow out of any high pressure system in a clockwise direction. It is common for the monsoon high to become centered just east of Arizona and then drift north and south throughout the summer. If it moves south of the state, the flow around it will bring dry midlevel winds from the west and, usually, hot and dry weather. When it moves north of the state, a more tropical flow allows tropical moisture and disturbances to enter the state from the east.

System movement

Moisture sources

Thee significant moisture sources influence the Arizona monsoon.

The first is the Gulf of Mexico, where a high pressure system known as the Bermuda High becomes centered over the western Atlantic Ocean east of the southeast U.S. coast, bringing midlevel winds and moisture into central Mexico. While a significant amount of low-level moisture is blocked by mountain ranges, mid- and upper-level moisture can eventually settle in the Mexican states of Chihuahua and Sonora and then get funneled into Arizona.

Moisture from the Gulf of California is distributed into Arizona via a process known as the gulf surge. This begins when tropical disturbances bring unsettled and relatively cooler weather to areas adjacent to the southern Gulf of California while hot dry conditions persist in the areas to the north. A pressure gradient between the two regions forms, and air begins flowing toward the low pressure area in the hot north. This breeze transports low-level moisture through the northern gulf region into Arizona.

The third source is tropical cyclones that form in the eastern Pacific and wander close to the west coast of Mexico. Occasionally they get caught in the flow and can reach Arizona in the form of remnant tropical moisture. This is the weather pattern expected to occur this week as Tropical Storm Javier sends moisture into Arizona.

Thunderstorm Development

Intense heat and rugged terrain

Arizona’s rugged terrain and summer heat provide another important ingredient for thunderstorm development: rising air and instability. Since air cools and expands as it rises and cool air is unable to hold as much moisture as warm air, rising air can become saturated and begin to condense water in the form of clouds. Wind patterns that force air up into mountainous regions and Arizona's relentless summer sunshine that rapidly heats the ground both encourage air to rise. If the atmosphere has a sufficient amount of water vapor, thunderstorms may form.

Cloud stages

Outflow Boundaries

Rising air that fuels thunderstorms will come back down eventually. When thunderstorms reach maturity, this displaced air becomes colder than its environment, creating a downdraft that falls rapidly. When the downdraft reaches the ground, it spreads out in all directions, much like water pouring out of a glass onto the floor. These sometimes-violent winds, known as thunderstorm outflow boundaries, can cause blowing dust and, if strong enough, can force air upward to form new storms. These boundaries occasionally collide with one another and displace even more air upward, aiding in the development of strong or severe thunderstorms.

Editor's Note: ASU’s School of Geographical Sciences & Urban Planning has partnered with ADOT to place graduate-level meteorology students in the ADOT Traffic Operations Center. This allows ADOT to have better information about weather conditions and more quickly determine how to deploy crews and communicate with the public.

By Dallas Hammit / ADOT Deputy Director for Transportation

While no one can control Arizona’s soaring summertime temperatures, each of us can take precautions to help ensure we’ll stay safe in the extreme heat.

Before you travel, it is important that you, your passengers and your vehicle are prepared for the trip ahead. It’s also wise to plan for the unexpected because you never know when a crash on a highway could cause a long traffic backup or even a vehicle breakdown could have you stranded for hours.

I know many drivers pack an emergency kit during the winter months. When they’re headed into snowy territory, they make sure to include gloves, blankets, ice scrapers and a bag of sand in case their vehicle gets stuck in the snow. A summer driving kit is just as vital and I would encourage you to pack one and keep it in your vehicle. Be sure it contains things like:

• extra water – enough for the driver, passengers and pets. You may also want to consider taking a cooler to keep extra drinking water cold.
• a fully charged cell phone and phone charger.
• an umbrella for shade.
• hats, sunglasses, sunscreen and loose-fitting cotton clothing to provide protection from sunburn.
• a first-aid kit and any necessary prescribed medication(s) and pain relievers.
• healthy snacks and a good road map that can provide possible alternate routes.
• safety gear, including a flashlight with extra batteries, safety flares, extra radiator water, a travel tool kit and battery cables.

There’s another item you might want to include and it’s one that most drivers might not think to carry – a reflective vest. It’s a good idea to have one and it can help ensure you are seen by other motorists if you are ever standing on the side of the road because of a breakdown or crash. I recently visited Germany and learned there is actually a law in place requiring all vehicles to have a reflective vest on board. Drivers there must wear that vest when they exit their vehicle and can face a fine if they don’t have one.

Please visit ADOT’s extreme heat web page for more information and tips. There you’ll discover ways to prep your vehicle for a trip in the heat, including:

• Fill your fuel tank and try to keep it at three-quarters full. Running out of gas in a remote location is dangerous in extreme heat
• Heat can take a toll on a vehicle’s battery. Consider having yours checked, especially if it’s more than three years old
• Check engine coolant levels and add coolant if necessary. Never remove your vehicle’s radiator cap when the engine is hot
• Check engine belts and fluids (motor oil, transmission fluid, brake fluid and power-steering fluid)
• Tire condition is important to monitor. Traveling with under- or overinflated tires on hot pavement can lead to a blowout. Make sure your tire pressure is at the vehicle manufacturer’s recommended level. Remember to check the spare tire, too
• You’ll also want to check your windshield wiper blades and replace them if necessary, so they’ll work if you encounter monsoon weather
• Make sure your vehicle’s air conditioning system is functioning properly
• Before you hit the road, you can visit az511.gov or dial 511 for updated road and weather conditions

As always, I ask that you not only review these safety recommendations yourself, but share and discuss them with your loved ones – it could make a difference.

Editor's Note: More safety messages from Dallas Hammit, ADOT's state engineer, are available at Driving Safety Home on azdot.gov.

By Caroline Carpenter / ADOT Communications

The El Niño forecast has had many, including people at ADOT, planning for downpours in the desert and lots of snow in the high country.

So what happened, and is it too late for a wet spring? We went to ADOT meteorologist Paul Panhans for some answers.

Q. Where has the rain gone?

A. El Niño is alive and well, but the upper atmosphere isn’t cooperating. We have been plagued by high pressure to our west, which is carrying the moisture away from Arizona to the Pacific Northwest.

Q. How exactly has El Niño played out from a meteorologist's perspective?

A. We have experienced well below the precipitation expected for an El Niño year. However, the Pacific Northwest in January and February saw above average precipitation. This trend continued into the early weeks of March. There also is a definite weakening of El Niño. The current forecast has El Niño dissipating by mid-summer, followed next fall or winter by a La Niña event with lower than normal precipitation.

North America Precipitation Probability Map

Q. What normally happens during an El Niño?

A. El Niño is caused by cyclical atmospheric pressure changes occurring every two to five years that increase surface ocean temperatures off Mexico, Central America and South America. Because it increases ocean temperatures, more water evaporates. If atmospheric circulations cooperate, they can push this added atmospheric moisture into the Southwest and cause above normal precipitation in the fall and winter.

Q. What might happen in the few remaining months of El Niño?

A. Even though this has been a slow El Niño year in terms of precipitation, that could easily change. The high pressure to our west could move out, and tropical moisture could move into the Southwest. The three-month outlook graphic below from the NOAA Climate Prediction Center suggests there's still a chance for some moisture before El Niño dissipates over the summer.

By Kim Katchur / ADOT Communications

Hard as it may be to believe given the record temperatures we've had recently, this is still a season for snow in Arizona. Because of that, ADOT has snowplow drivers at the ready, including drivers of our new TowPlow.

Back in February, TowPlow inventor Bob Lannert came to the North-Central District to train our drivers. And as you’ll see in the video above, Mother Nature provided the drivers – and our video crew – a significant snowstorm that same weekend, making the experience even more valuable.

As we shared last month, the TowPlow is a steerable trailer with a 26-foot blade that’s attached to the back of a regular snowplow truck. The combination, able to plow a 24-foot-wide path, lets ADOT clear more lanes in less time using less fuel.

The TowPlow joins ADOT’s fleet of 200 traditional snowplows and is assigned to 20 miles of I-40 between Williams and Bellemont west of Flagstaff.

TowPlow drivers, as with those operating any ADOT snowplow, need cooperation from other motorists. That includes staying at least four car lengths behind snowplows, slowing down and being patient.

Get more driving tips and find useful information over on our “Know Snow” Web page. You can also check out our previous blog posts and videos for even more about how ADOT prepares for the snowy season.

When Arizona’s latest winter storm hit Sunday evening, ADOT crews went into high gear. Snowplow operators across northern Arizona and other areas where snow fell worked into the night and on through to Monday evening before the storm let up. Their efforts helped keep highways open and traffic flowing.

In ADOT’s North-Central District, based in Flagstaff, Maintenance Engineer Kurtis Harris says a combination of equipment, people, training and advanced planning make for a successful response to a winter storm. And that doesn’t include just the 100-plus snowplow operators on call when the storm hit.

Three motorist-assist groups were stationed on I-17 and parts of I-40 to respond to any drivers in need of help. These crews travel in four-wheel drive vehicles equipped with salt, cinder, shovels and other equipment to help motorists and quickly radio requests for DPS or tow trucks.

“They look for stranded motorists or those who have slid off the road,” Harris says. “Getting stuck vehicles off the road or moving again goes a long way in preventing road closures.”

The snowstorm also gave the North-Central District a chance to try out ADOT’s brand new TowPlow.

Never heard of a TowPlow? It’s a steerable trailer with a 26-foot blade that’s attached to the back of a regular snowplow truck. The combination, able to plow a 24-foot-wide path, lets ADOT clear more lanes in less time using less fuel. ADOT’s TowPlow joins a fleet of 200 traditional snowplows and is assigned to 20 miles of I-40 between Williams and Bellemont west of Flagstaff.

Harris also notes that during storm events, road-closure teams stand by, ready with cones and equipment to quickly and safely set up closures and detours when necessary.

During a winter storm, much of the action is out on the roads, but there’s also a ton of work and coordination happening behind the scenes.

“All of us have a responsibility for keeping the roads open and safe,” Harris says.

That of course extends to drivers, too.

For snow safety tips, visit azdot.gov/KnowSnow. You can also revisit our previous posts for more information on how ADOT prepares for the winter storm season (this video in particular is a good one to watch, if you want a behind the scenes look at how snowplow drivers train).