Latest news with #MichaelCrimmins
Yahoo
02-06-2025
- Climate
- Yahoo
When does the Arizona monsoon season start, and how much rain will the Phoenix area see?
Arizona's monsoon season starts in June and goes through the end of September, but that doesn't guarantee storms will pop up immediately. Most experts agree that there's no way to know exactly when black clouds, streaks of lightning and walls of dust will appear. Forecasting the monsoon is notoriously difficult. The June date is more for public awareness than a definitive arrival time for monsoon storms. 'We're really flying blind,' said Michael Crimmins, a climatologist at the University of Arizona. 'This feels like we could be two weeks out from the monsoon and still have no idea how it's going to turn out.' Every monsoon is different, and forecasting can be hit or miss. After a disappointing 2024 monsoon and an abnormally dry winter that deepened drought conditions, experts say Arizona needs rain. Here's what to expect for hopefully a more fruitful 2025 monsoon. The monsoon officially starts June 15 and goes until Sept. 30. Climatologists have studied the monsoon and variables that can influence a season's severity for decades, but correlations in the research are weak or inconsistent, according to Crimmins. For example, some research shows dry winters can be followed by wet summers. 'It's a weak correlation,' Crimmins said. 'We're not sure of the mechanism, and it's not stable over the last hundred years. There have been decades where that worked, decades where it hasn't.' There are also weak correlations between the monsoon and El Niño-Southern Oscillation, or ENSO, which is a natural cycle that reflects the relationship between ocean temperatures and atmospheric conditions stemming from the Pacific Ocean. El Niño, La Niña and a neutral period are ENSO cycles that can have a big effect on the weather, and these events provide some of the best insights for seasonal outlooks for the U.S. La Niña was present over the winter, which was partly responsible for abnormally warm and dry weather in the Southwest, but conditions have transitioned back to neutral heading into the summer. 'When you don't have either El Niño or La Niña with a neutral pattern, which is what we're at right now, we don't have much to go on,' Crimmins said. There is some evidence that El Niño can delay the onset of the monsoon, while a strong La Niña can trigger an earlier start. 'What I've seen in the climate models so far is they're shrugging,' Crimmins said. 'They're not leaning in either direction, so we're going to be week-by-week looking through June looking for a start.' Even when the monsoon arrives, predicting day-to-day storms and overall activity throughout the season is tricky. The season starts when a ridge of high pressure settles over the Four Corners region. The winds reverse, transitioning from westerly to southeasterly winds, pulling moisture into the Southwest from the Gulf of California, the eastern Pacific Ocean and sometimes the Gulf of Mexico. This high-pressure subtropical ridge slowly travels north during May and June, bringing heat and humidity as it moves toward the Four Corners. Meteorologists also watch hurricane and tropical storm activity in the eastern Pacific and warming surface temperatures in the Gulf of California, which can provide moisture for monsoon storms. Even when the monsoon ridge is positioned over the Four Corners, it doesn't guarantee storms, and forecasting is still complex. 'The monsoon doesn't mean we're going to get rain every day,' said Erinanne Saffell, Arizona State's climatologist. 'We can look a few days ahead, but it's a better understanding looking at the morning forecast and getting a sense of whether we have warm air rising, is there enough moisture in the atmosphere to create clouds and will the clouds get big enough to drop moisture?' Thunderstorms are created from warm air rising, or convection, while there is moisture in the atmosphere. Meteorologists will look at dew point temperatures to gauge how much water is in the air. If there is enough water in the atmosphere, clouds will begin to form. Moisture, warm air rising and instability in the atmosphere are the three main ingredients of a monsoon storm. But even if those conditions are present, storms may not leave the mountains. For monsoon storms to reach places like Phoenix or Tucson, weather systems in the mountains must push out air, forming new thunderstorms. Some storms die out before they hit the metro areas. In terms of actual rainfall, Arizona could see roughly two inches in lower deserts, including the Phoenix area, and up to 16 inches in mountain ranges. Metro Phoenix typically experiences about 10 days with measurable rainfall during the monsoon, while the higher mountainous areas see roughly 30 to 50 days of rainfall. The weather service projected Phoenix with a 43% chance of above normal precipitation during the monsoon, a 33% chance of near normal precipitation and a 24% chance of having below normal precipitation. For context, Phoenix had an average of 2.43 inches of rainfall during monsoon seasons from 1991 through 2020, according to the weather service. Other cities that leaned toward having above normal rain included Tucson, Flagstaff, Prescott, Kingman and Show Low, among others. The weather service recommended people check their local forecasts before going out and ensure they're signed up to receive weather warnings. This article originally appeared on Arizona Republic: Arizona monsoon season starts in June and goes through September
Yahoo
30-01-2025
- Climate
- Yahoo
Missed it by a day: Why has the 52-year-old record for no rain in Phoenix lasted so long?
Phoenix finally got a taste of rain Wednesday, but just barely. A scant 0.01 of an inch was recorded at Sky Harbor Airport, ending the city's 159-day dry streak, the second-longest on record. While Phoenix is known for its arid weather, receiving 7.22 inches a year on average at Sky Harbor, this dry spell stood out from the rest. "It doesn't rain here a lot, but we've got these two seasons that usually will cut these dry spells down," said Michael Crimmins, a climatologist at the University of Arizona. "Overall, this winter has been extremely dry, but Phoenix really stands out as having the longest dry stretch." The streak ended just one day shy of tying the current record of 160 days without measurable rain in Phoenix, a record set in 1972. And it's still dry. With the .01 of an inch recorded Wednesday, Phoenix is still 2.68 inches below average since Oct. 1, the start of the water year. Here's everything to know about Phoenix's dry spell, why the record is so hard to break and how other cities across the Southwest are faring during this unusually dry winter: Topography and seasonal weather patterns play a big role in Phoenix's dry climate, setting the stage for long dry periods. "Phoenix is standing on its own a little bit in Arizona. Phoenix is low desert and away from the mountains," Crimmins said. "It's easier to get precipitation in the high country." Phoenix is surrounded by mountain ranges that can block moisture from reaching Phoenix. It's also far from large bodies of water that provide a consistent source of moisture to fuel precipitation. Phoenix's low elevation prevents atmospheric lifting mechanisms that produce precipitation in higher elevations. The rains can travel from the mountains, but it doesn't always happen. During the monsoon, the sun heats the mountains first and spurs conduction for storms. But as the systems descend, dry air at lower elevations and higher temperatures can cause a storm to die out before it hits the valley. Low humidity and high temperatures also play a role, with extreme heat and dry air causing rapid evaporation in the Phoenix area. It's a dry one: It's now a La Niña winter, but it's a weak one. What to know about it in Arizona But why is the dry streak record so resilient? How has it stood for more than 52 years? Although rain is less common in Phoenix than in much of the country, it typically measures a few inches of rain every year during the "wet" seasons in the summer and winter. "We've got the monsoon in the summer and the winter weather pattern that can bring some precipitation," Crimmins said. "So that's just the seasonal cycle here — you get some weather system on the edges that usually breaks up the dry spells." But this year was different. The monsoon began early with some showers in June but largely died out by the end of the summer. The last day of measurable rainfall was Aug. 22, beginning the second-longest dry streak on record. "The dry spell was a byproduct of the monsoon not being great. We were already in trouble when the monsoon started to dry up," Crimmins said. Arizona can get some moisture from fall tropical storms to the south, but September and October remained extremely hot and dry in Phoenix. By December, Crimmins said the winter weather patterns that can bring precipitation south remained over British Columbia, one of the early signs of La Niña conditions. La Niña is a climatological event that typically brings drier and warmer conditions to the Southwest, stemming from colder-than-normal ocean temperatures in the eastern Pacific. This dry spell was also unusual because of its timing. Dry spells in Phoenix tend to occur in the winter and spring until the monsoon begins. "It's totally normal to have 90-day dry spells in the spring until the monsoon kicks off," Crimmins said. "Phoenix recorded zero precipitation from Sept. 1 to now, and that hasn't happened before in the records at Sky Harbor." Even during historically dry years, there were always two or three days that would break up the dry spells, according to Crimmins, making lengthy, 140-day-plus dry streaks uncommon. Rising heat: With little rain, long heat waves, 2024 will end as the warmest year on record in Phoenix Phoenix isn't the only city with an uncharacteristically dry few months. Las Vegas' dry streak is even worse — Wednesday marked the city's 200th day without measurable rain. This is also the second-longest dry spell for Las Vegas, but the longest streak is still a ways off. The current record was set in 2020 with 240 days. It's been a dry winter across Arizona. Flagstaff has had one of its driest cold seasons on record with just 5 inches of snow since Oct. 1, compared to a 47.8-inch average for that time frame. Yuma is also experiencing an ongoing dry spell at 174 days without measurable rain, but that does not come close to its record: 380 days, more than a full year with no rain in 2002 and 2003. While Phoenix's dry spell has ended, residents likely won't see much rain in the coming months. "Every day we get closer to spring, the chances of our precipitation events start to drop off," Crimmins said. "This is not a drought buster by any means. It breaks up the dry spell record, but it's not doing a lot of work otherwise. Hayleigh Evans writes about extreme weather and related topics for The Arizona Republic and Email her with story tips at This article originally appeared on Arizona Republic: Why does the rainless record remain unbroken in Phoenix?
