We had a wet and cool August. The National Weather Service in Flagstaff published their monthly report for August. Northern Arizona was cool and wet. The wet piece probably surprises no one. The part I find interesting is that the cool temperatures and above average precipitation prevailed in most of Northern Arizona. Too often, we have a bimodal summer. Flagstaff had 2.2 inches over the average precipitation, and 3.8 degrees below normal. I usually think +/- 2 degrees is in the normal range.
August temperatures and precipitation data departure from normal for Northern Arizona locations. (National Weather Service Flagstaff)
The monsoon season may have one more wet session in store for us. As tropical systems continue to march up the West Coast, they may bring more moisture to are region. This weekend is the next big chance.
On Thursday, the Climate Prediction Center released new 1-month and 3-month long-range outlooks. They point to continued above normal precipitation for September, and September to November. They are below. I think the above average temperature waters off the West Coast and the Gulf of Mexico. El Nino continues to look iffy. Currently, another slightly drier period is coming next week.
Apologies to my readers. I missed all the action last week. I was in Germany when many areas had deluges on Monday and Tuesday. The videos on YouTube are remarkable.
One-month precipitation outlook for September 2014. (from the Climate Prediction Center)
3-month precipitation outlook for September-November 2014. (from the Climate Prediction Center)
In my last post, I pointed out that a drier period was ahead. What I had meant, and what the models foretold, was no rain for a week or so. That has not been the case. Thursday evening, a storm moved across the west side of Flagstaff dumping heavy rain across the area. Friday evening a storm hit central Flagstaff. I got about 1/3 of an inch of rain. I got more rain on Saturday, a mere 0.03 inches. This is drier than earlier in the week when I received over an inch.
This dry trend will continue for the next few days with a 30-60% chance of rain each day through Thursday. I think that in wet years, the forecast models run on the dry side, especially at long lead times. In dry years, they run on the wet side. The result is that more is on the way for this week.
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)
Monsoon, OutlooksComments Off on Dew points to fall, but hope for a week in the future
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.
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