What North Phoenix Can Expect from Hurricane Rosa’s Remains

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rainfall totals
The National Weather Service issued a Flash Flood Watch for Phoenix and other part of Arizona for Monday and Tuesday, along with this map showing rainfall from the remains of Hurricane Rosa could exceed 2 inches in Phoenix.

UPDATED 5:15 p.m. Friday, Sept. 28: Hurricane Rosa, which developed into a monster Category 4 storm late Thursday, is expected to gradually curve to the northeast, speed up and make a beeline for Arizona. While the course can’t be predicted with total accuracy, the National Hurricane Center’s best bet has the storm weakening significantly—top sustained winds were near 140 mph Friday morning—but bringing boatloads of moisture into Arizona starting late Sunday or early Monday.

Editor’s Note: This archived article is from Friday. Click Here for the Latest Updates on Rosa.

If Rosa follows the expected path, North Phoenix could get anywhere from 1 to 3 inches of rain, according to the National Weather Service, with the highest totals likely near mountains, such as in Anthem and New River. The greatest chance for widespread showers will be Monday and Tuesday—a Flash Flood Watch has already been issued for those days.

hurricane rosa water vapor
This satellite image, captured today (Sept 28, 2018), shows water vapor associated with Hurricane Rosa and other tropical moisture.

‘Prolonged Rain’

Whereas monsoon storms are often isolated, capricious and violent, Rosa’s remains will be more zombie-like: longer, slower and persistent. Rain could continue intermittently into Wednesday, according to the NWS. 

“We might see some isolated thunderstorms, but it’s heavy and sometimes prolonged rain that will be the concern,” said Andrew Deemer, a meteorologist at NWS office in Phoenix. “The biggest threat will be flooding from excessive rains.”

The storm’s winds are unlikely to cause the kind of damage typical the worst monsoon storms, Deemer said.

Click this video to see how much uncertainty there is in the storm’s predicted track:

Before Rosa Arrives

Despite Rosa’s current strength, it will move over cooler ocean waters this weekend, robbing it of the heat that fuels hurricane winds. The storm will begin to die. Slowly. As it glides over land, the fuel and moisture supplies will be cut off.

Top sustained winds will have dropped below hurricane force before Rosa reaches Baja and then enters southwestern Arizona. The storm will weaken further to a tropical depression—with winds below 39 mph—likely before it exits Arizona to the northeast.

Rosa’s rains are expected to reach North Phoenix long before the storm’s center arrives. As was the case with Florence in the Carolinas, rain clouds extend more than a hundred miles ahead of, and behind, the storm center. And precipitation totals will likely vary by elevation.

“Locations with higher terrain, even the North Valley, can ‘benefit’ from orographic lift,” Deemer told North Phoenix News. “Essentially, the moisture is forced to rise over the terrain, which can lead to the formation of showers or storms. In this case, even though the rain will be widespread, the terrain can enhance the shower activity.”

Is This Normal?

The forecast is not entirely certain—the storm’s path could shift—but the odds of rain are about as high as are typically given this time of year, especially so far in advance. Officially, as of this morning, the NWS calls for a 40 percent chance of showers Sunday night, 50 percent Monday, 80 percent Monday night, and 60 percent on Tuesday.

It’s not unusual for tropical systems to reach the Valley this time of year, Deemer said.

A review past hurricanes and tropical storms affecting Arizona finds several whose remnants have dumped an inch of rain or more on Phoenix, including at least four that dropped 2 inches or more in the past 100 years. In 1970, remnants of a tropical system killed 23 people in Arizona and dumped nearly a foot of rain in one mountainous area of the state.

This article was updated at 5:15 p.m. Friday, Sept. 28.

hurricane nora
Hurricane Nora in 1997, moving out of the Pacific Ocean across Baja California and into Arizona. Image: NOAA

Help Save Our Community
Small businesses are the lifeblood of our country and even more so this community. Supporting local businesses during this crisis can help keep our community economically viable. Please strongly consider supporting the businesses below, In&Out Magazine's display advertisers, as well as those in the Classifieds section of the magazine (see the full April 9 issue in PDF form). Many of these businesses have been part of the fabric of this community for two decades, not just serving our professional, service and retail needs but stepping up to support local charities, sports teams and so much more. Tip: If you know you’ll need to schedule a service, consider contacting a local business you trust and paying the standard fee for the deferred service. The links below go to their web sites.

Adult & Pediatric Allergy Associates • 602-242-4592
Anthem Senior Living • 602-909-9550
Appliance Pros • 502-501-5501
Business Network of Anthem • 623-455-9630
Carroll Law Firm • 623-551-9366
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Kodiak Roofing • 602-501-7717
Luv My PC • 480-703-6609
Merrill Gardens • 623-201-4881
North Valley Water Solutions • 623-551-0515
Preferred Business of Anthem • 623-551-0523 
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RE/MAX Professionals - Mike Higgins • 623-640-7502
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SonoranScapes Landscaping • 602-842-9948
State Farm Insurance - Justin Simons • 623-551-3700
Storage at Anthem • 623-226-8634
Sunset Cabinets • 623-687-6579
Thompson & McGinnis Attorneys at Law • 602-952-2666
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Titan Pest Control • 623-879-8700
Wyman Plumbing & Mechanical • 623-551-6688

For more local businesses, see In&Out Magazine Classifed Ads >>>  
 
Robert Roy Britt
NoPho resident Robert Roy Britt has written for In&Out publications since its inception in 2005. Britt began his journalism career in New Jersey newspapers in the early 1990s. He later became a science writer and was editor-in-chief of the online media sites Space.com and Live Science. He has written four novels. Email the author.
Robert Roy Britt on Email

Robert Roy Britt

NoPho resident Robert Roy Britt has written for In&Out publications since its inception in 2005. Britt began his journalism career in New Jersey newspapers in the early 1990s. He later became a science writer and was editor-in-chief of the online media sites Space.com and Live Science. He has written four novels. Email the author.

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