It’s hard to believe since it rained all night last night, but another break in the action is ahead. The weekend might be a bit wet, but next week is looking mostly dry.
I think this is due to the repetitive formation of hurricanes off the coast of Central America. These storms keep forming and rolling off to the west. This pattern shifts the monsoonal flow. I haven’t checked the exact numbers for Flagstaff, but we probably surpassed the average precipitation total for August with this current storm.
Last night we saw the first part of a wet week. This week, we should be inside the monsoonal flow. And, I think there is plenty of warm water to support an ongoing rainy season. The Pacific Coast of North American, all the way down to Central America is quite warm compared to normal. This can help with moisture supply to the Southwest.
Although the equatorial waters west of Peru seem warm, they have actually dropped. It still doesn’t look like the wind shift needed to support El Nino will happen. Stay tuned.
Global sea surface temperature anomaly, August 10, 2014. (National Centers for Environmental Prediction)
For the next four days, some of the forecasts and the computer models show as much as an 1.5-2 inches of rain for parts of Northern Arizona. This will give us a good start to August. The scope of the precipitation over the next few days isn’t reflected in every forecast. Some, like the NOAA’s Graphical forecast and the National Weather Service’s forecast seem much drier and warmer. For instance, if you are heading to Lake Powell, I expect Sunday will be cooler(everyone may not think high 80s, low 90s are cool) and wetter compared to normal.
Looking deeper into August, the 6-10 and 8-14 day outlooks have dry conditions moving into Arizona. Dry period during a reasonably wet monsoon season isn’t unusual. Later today, the Climate Prediction Center should issue a new 30-day outlook. The question is whether or not the long-range outlook will continue to forecast above average precipitation.
North American Mesoscale Model of four-day total precipitation. (National Centers for Environmental Prediction, 31 July 2014)
Starting today, the dew point temperature is going to fall. By this weekend, our dew point temperature will be in the 20s. This is well below the damp 50+ dew point temperatures we need for good thunderstorm activity. But, the moisture should build back into the region by early next week.
Below are the dew point outlooks for Friday night and midday Monday. Notice on Friday night that white covers Northern Arizona indicating dew points at or below 25 degrees F. By midday Monday, a knuckle of moist air moves into Northern Arizona bring the dewpoints back to the mid 40s. Hopefully, by Wednesday of next week, we may see a return of thunderstorm activity.
Dew point temperature outlook for Friday night 18 July 2014. From the National Center for Atmospheric Research.
Dew point temperature outlook for midday Monday, 21 July 2014. From the National Center for Atmospheric Research.
Looking out 2 weeks, you might think so. Today is the last day in the current forecasts and outlooks when Northern Arizona can strongly expect rain. The winds are going to shift back to a southwesterly origin and bring dry air. Below are the 6-10 and 8-14 day outlooks. The Climate Prediction Center issues new 30 and 90-day outlooks on Thursday.
As a side note, it looks more and more like El Nino is going to fail before it is up and running. I get in to that detail later. However, this probably isn’t the driver behind our monsoon season.
6-10 day precipitation outlook from the Climate Prediction Center. (14 July 2014)
8-14 day precipitation outlook from the Climate Prediction Center. (14 July 2014)
The monsoonal flow will shift a bit to the east for today and the weekend. This means less rain for western Arizona. As you can see in the satellite water vapor image below, an orange knuckle of dry air has moved into the state. Not to worry, next week we should see more rain.
A lot of discussion, in one-on-one conversations and on the internet, about next winter’s El Nino. Retired climate scientist Bob Tisdale has been tracking the development of the this year’s El Nino. You can visit his blog via that link to catch up on the deep details. As of his last update, the El Nino conditions seem to have not fully developed. It’s not just the temperatures that drive El Nino, it’s the winds. Currently, the trade winds haven’t shifted to sustain El Nino conditions. Stay tuned, it could still happen.
Water vapor image. Orange indicates dry air. From the National Weather Service.
To kickoff the monsoon season in fine form, the Flagstaff Airport received a record-breaking 1.89 inches of rain on July 4, 2014. I didn’t see it reported in the Arizona Daily Sun’s website.
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
1239 AM MST SAT JUL 05 2014
...RECORD DAILY MAXIMUM RAINFALL SET AT FLAGSTAFF AZ AIRPORT...
A RECORD RAINFALL OF 1.89 INCH(ES) WAS SET AT FLAGSTAFF AZ AIRPORT
YESTERDAY. THIS BREAKS THE OLD RECORD OF 1.85 SET IN 1986.
More is on the way. Considering that the airport’s normal is 2.61 inches, rainfall for this month should not find it terribly hard to hit normal. There are some dry time periods over the horizon. Also, not everyplace received that much rain. Here is the rain totals for the month so far as independently reported to Rainlog.org at the University of Arizona. The monsoon season has had a healthy start.
Month to date rainfall for the Flagstaff area. July 7, 2014. (Source rainlog.org)
Dew point temperatures across Arizona will move higher over the next few days. This means more widespread thunder showers across the area. A friend of mine, TB, was mentioning his plans to hike around one of the creek beds near Sedona for the 4th of July. Flash flooding is a serious issue in the desert. Here are some flash flooding safety rules from the National Weather Service (in Ohio?):
In hilly terrain, flash floods can strike with little or no advance warning. Distant rain may be channeled into gullies and ravines, turning a quiet stream into a rampaging torrent in minutes. Never camp on low ground next to streams since a flash flood can catch you while you’re asleep.
Do not cross flowing stream on foot where water is above your ankles.
If you are driving, don’t try to cross water-filled areas of unknown depths. If your vehicle stalls, abandon it immediately and go to higher ground. Rapidly rising water may sweep the vehicle and its occupants away. Many deaths have been caused by attempts to move stalled vehicles.
Be especially cautious at night. It’s harder to recognize water danger then.
Don’t try to out race a flood on foot. If you see or hear it coming, move to higher ground immediately.
Be familiar with the land features where you live, work, and play. It may be in a low area , near a drainage ditch or small stream, or below a dam. Be prepared!
Stay tuned to NOAA Weather Radio for the latest statements, watches and warnings concerning heavy rain and flash flooding in your area, report it to the National Weather Service.
I’m bugged by the fact that a quick search for “flash flood” on the NWS Flagstaff website didn’t turn up a document like this. Something that isn’t stressed in this list that is very important is that the storm can be far away and cause a flash flood where you are. Be aware of the weather upstream from your location. A small creek bed can be the sole drainage for hundreds of thousands of acres. If you are in a canyon, you may not be able to even see the storm. They do have a good webpage set up for monitoring the area around the Slide Fire.
Here is the North American Mesoscale precipitation model outlook through midday on Sunday.
Total precipitation from July 3 to July 6, 2014 from the North American Mesoscale Model at the Climate Prediction Center.
The 8-14 day outlooks continue to look wet. Thursday, the 6-10 Day outlook from the Climate Prediction Center looks wet, too. This 6-10 day outlook includes July 2-8. The signs are good for a change to the monsoonal flow next week.
8-14 day precipitation outlook from the Climate Prediction Center, June 26, 2014.
6-10 day precipitation outlook from the Climate Prediction Center, June 26, 2014
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