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)
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)
The good news is that most of Northern Arizona remains in the above average precipitation zone for the summer. Still, I don’t believe El Niño is the link. There are a combination of factors. The Climate Prediction Center issued a new 3-month outlook last week.
The bad news is that the winds may not leave for another two weeks. The winds we have experienced lately are due to the jet stream moving far to the south. It would have been a blessing in the winter. But now, it delays the monsoon season.
It’s still nearly a week away, but next Sunday and Monday could be rather wet if the US Navy NoGAPs forecast is correct. This storm doesn’t show up in the GFS forecast, but there is something weak in the Global Ensemble forecast. We will see.
US Navy NoGAPs computer model for Sunday afternoon June 13, 2014
This weekend will be another cooler, wetter weekend. The precipitation forecast in the North American Mesoscale model shows Flagstaff in the one-half to three-quarters of an inch of precipitation zone. This could be the most significant storm in months. We should see mostly unfrozen precipitation, but if temperatures are low enough, some very temporary snow accumulation is possible.
North American Mesoscale model precipitation outlook through Sunday morning. From the Climate Prediction Center.
I noticed the new 3-month outlook from the Climate Prediction Center. For May, June and July, they are forecasting above average precipitation for the 4-corners region. Flagstaff is at the edge of the “green” zone. The questions I have are about the emerging potential for an El Nino building over the summer. I don’t think El Nino summers are very wet, but I need to look at some data and haven’t had the time.
For now, this weekend looks wet and cool. We need the water.
3-month(May-July) precipitation outlook from the Climate Prediction Center.
Well, a small chance of scatter showers looks pretty good now. But, the reality is that we won’t see much precipitation. For most of the Easter Weekend, we will have clouds and cooler temperatures and occasionally light rain. It’s very dry out there.
84 hour total precipitation NAM outlook from the Climate Prediction Center.
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