Monsoon season to start in earnest next weekend

 Climate, El Nino/La Nina, Models, Monsoon, Northern Arizona Weather, Outlooks  Comments Off on Monsoon season to start in earnest next weekend
Jul 022017
 
Dew point temperature outlook for Saturday afternoon, July 8, 2017, from the GFS model at TropicalTidbits.com.

In June, there have already been several thunderstorms and rain showers. But, a sustained monsoonal flow has been mostly absent. Dew point temperatures will rise throughout the week, with most Arizona being in the mid-40s by next weekend.

Dew point temperature outlook for Saturday afternoon, July 8, 2017, from the GFS model at TropicalTidbits.com.

Dew point temperature outlook for Saturday afternoon, July 8, 2017, from the GFS model at TropicalTidbits.com.

While isolated thunderstorms would be come more frequent this week, next saturday is the first day that seems to have pretty good areal coverage.

24-hour total rainfall forecast for next Saturday, July 8, 2017, from the GFS model at TropicalTidbits.com.

24-hour total rainfall forecast for next Saturday, July 8, 2017, from the GFS model at TropicalTidbits.com.

One last note, the start of the season should be strong. The 6-10 and 8-14 day outlooks from the Climate Prediction Center show above average precipitation. The longer range 1 and 3 month outlooks only show normal precipitation chances. I think these may change the next time they are run since the El Niño outlook has a decreased likelihood of it occurring this year.

6-10 day precipitation outlook from the Climate Prediction Center.

6-10 day precipitation outlook from the Climate Prediction Center.

 

8-14 day precipitation outlook from the Climate Predication Center.

8-14 day precipitation outlook from the Climate Predication Center.

 Posted by at 9:13 am

Here’s an animation that makes the point.

 Climate, Models, Northern Arizona Weather, Outlooks  Comments Off on Here’s an animation that makes the point.
Feb 162017
 
Animation of total precipiation from 4 different computer models runs for the same storm. (From Tropical Tidbits)

The computer GFS computer model is all over the place. Here is an animation of 4 images. All 4 images report total project precipitation through next Tuesday evening. Notice, it hasn’t started to rain or snow at this time, so that the start time doesn’t matter. The precipitation amounts are widely different. It looks like Flagstaff is in the 0.5 to 3 inches range, depending on which run you like.

The current Navy model, which doesn’t automatically calculate totals from more than 6 hours, appears to forecast a couple inches of precipitation. Currently, the GFS model has predicted more snowfall than earlier this week.

Animation of total precipiation from 4 different computer models runs for the same storm. (From Tropical Tidbits)

Animation of total precipiation from 4 different computer models runs for the same storm. (From Tropical Tidbits)

 Posted by at 11:33 am

After a dry start, will Flagstaff hit average precipitation for February

 Climate, Northern Arizona Weather  Comments Off on After a dry start, will Flagstaff hit average precipitation for February
Feb 112017
 
Forecasted total precipitation through February 27, 2017 from the GFS model. (Tropical Tidbits)

But first, what is average? In the grand view, we have limited data. The National Weather Service maintains a record going back to 1898. Between 1898 and 1950, the weather station site moved 4 times. This complicates the precipitation record because of the effects terrain can play on precipitation amounts. Precipitation has been measured at the Flagstaff airport since 1950.

In the back of my head, I thought average February precipitation was about 2 inches. As I looked quickly at the last few years, 2 inches seemed like a stretch. The last ten years averaged out at 1.47 inches. Ouch! What about the rest of the data? I went back, 10 years at a time, to look at how the averages change.

1957-1966 1.84
1967-1976 1.89
1977-1986 2.54
1987-1996 3.28
1997-2006 1.51
2007-2016 1.47

Wow! The last decade was less than half of the 1987-1996 average. The standard deviation was 0.7 inches across this set of data. Since 1950, the average is 1.98 inches.

Back to the simply question, will Flagstaff get average precipitation in February? From a total water precipitation point of view, yes. Below is the total projected precipitation through the end of the month from the GFS model via Tropical Tidbits. It looks like Flagstaff is in the 1.5-2.0 inches range.

On the other hand, much of it will be rain, not snow. That doesn’t seem to be average. For this weekend’s storm, the snow levels are projected to be high, 8000-9000 feet.

Forecasted total precipitation through February 27, 2017 from the GFS model. (Tropical Tidbits)

Forecasted total precipitation through February 27, 2017 from the GFS model. (Tropical Tidbits)

 

 Posted by at 12:08 am

Wet, cold…wintry

 Climate, El Nino/La Nina, Northern Arizona Weather  Comments Off on Wet, cold…wintry
Nov 032015
 

Today will start wet in Northern Arizona. Around night fall, maybe a  bit later, the rain should change to snow and start our El Nino winter. Almost an inch of water could fall from the skies in various forms. As it is often the case for these early winter storms, timing of the switch to snow is everything. A fairly dry period will follow as the winter storm pattern continues to develop.

60-hour total precipitation (North American Mesoscale Model) from the Climate Prediction Center.

60-hour total precipitation (North American Mesoscale Model) from the Climate Prediction Center.

 Posted by at 2:57 am

Is Flagstaff wetter than Munich?

 Climate, Northern Arizona Weather  Comments Off on Is Flagstaff wetter than Munich?
Oct 302015
 

My current frame of reference is Munich. It’s been mostly foggy with cool clear nights cause the still relatively warm moist ground to product fog. But, rainfall and first snow have been on my mind.

3.68 inches of rain have fallen in Flagstaff in October. This is more than double the normal amount. Below is the rainlog.org picture for October in the Flagstaff Area. As always, there is much variability. Overall, it was a wetter than normal month for Flagstaff, but very far from a record. This make the 12 month precipitation total 27.39 inches.

My weather station here in Munich has measured 3.5 inches of rain. Munich’s average precipitation is 2.68 inches at the airport. So, both Flagstaff and Munich have had a wet October, but I think Flagstaff has been wetter.

October rainfall for the Flagstaff area reported on rainlog.org. (through October 30, 2015)

October rainfall for the Flagstaff area reported on rainlog.org. (through October 30, 2015)

 Posted by at 11:29 pm

If you liked last week, you’re going to like the rest of the month.

 Climate, Models, Northern Arizona Weather, Outlooks  Comments Off on If you liked last week, you’re going to like the rest of the month.
Oct 102015
 

It’s been a while since my last post. This is all thanks to Apple. I bought a new laptop because using my big MAC in Germany isn’t practical anymore. We just don’t have the room for it. After a week of using the new laptop, the arrow keys broke. The first chance I had, I took it to the Apple Store to have it replaced or fixed. They wanted to fix it, but the part would take some time. I could still use the computer, but not easily. Then I took it back when the part came in. They said I would receive a message in 3-5 days. After a week I called. They told me it would be another week before they got to it. Sheesh. I feel like just gave Apple a loan of over a thousand bucks for a month! This is not Steve Jobs’ Apple!

Deep cleansing breath in…and out.

So, I missed blogging about the rain last week. With the airport receiving 1.27 inches of rain, Flagstaff is well on its way to an above average rainfall month. The average October precipitation in Flagstaff since 1950 is 1.54 inches. With the outlooks for the next few weeks, we should easily surpass the average.

I’ve taken the current 6-10 day, 8-14 day, 3-4 week, 1 month and 3 month outlooks and made an animated gif. This is below.Most of Arizona is comfortably inside the above normal chances for above average rainfall for all time periods.  El Nino and the disappearance of the Ridiculously Resilient Ridge are driving this. I wonder when the first big snow will show up. It could be this month.

Also, the North Atlantic is colder than normal. This can also mean a wetter than normal winter. I plan to do some more on this topic when I get my laptop back. The spreadsheets are on the laptop.

Animated gif of 6-10 day, 8-14 day, 3-4 week, 1 month and 3 month precipitation outlooks from the Climate Prediction Center.

Animated gif of 6-10 day, 8-14 day, 3-4 week, 1 month and 3 month precipitation outlooks from the Climate Prediction Center.

 Posted by at 12:29 am
Sep 252015
 

In the last two months, the Climate Prediction Center has not been very accurate with their 1-month precipitation outlooks. July and August precipitation amounts were close to average. September’s precipitation amount is running well below average. On the other hand, they we right about April, May and June. The long-range outlooks continue to show a strong, El Niño winter.

They have now released an Experimental 3-4 week Outlook. This was a gap in their forecasting portfolio. On their home page, They had outlooks for 6-10 days, 8-14 days, 1 month, 3 months, Hazards and Drought. Below is the current 3-4 week precipitation outlook.

Precipitation outlook for weeks 2 and 4 in the future from the Climate Prediction Center.

Precipitation outlook for weeks 2 and 4 in the future from the Climate Prediction Center.

Looks very wet. However, in their discussion they state:

Following ensemble prediction system forecasts from the CFS, ECMWF and JMA, the forecast for the week 3 and 4 period favors above-median precipitation for the Southwest region extending eastward across Texas into parts of Louisiana. This is somewhat consistent with statistical forecasts based on El Niño, however this tool does not appear to have great skill for precipitation forecasts under El Niño conditions at this time of year, indicating the probable influence of additional climate variability on the precipitation pattern.

So, we will have to wait and see. I think late September through November are the toughest months for forecasting Northern Arizona’s weather.

It appears the Ridiculously Resilient Ridge and the related Pacific Blob are going away. Deep details are at The California Weather Blog. The Ridge created the Blob, which reinforced the Ridge, which reinforced the blob, and so on. The ridge is breaking down. The Blob should also disappear over the winter. This is very good news for California and may help reinforce a strong El Niño winter for Arizona.

One last thought, the Atlantic Multidecadal Oscillation is continuing to look like it has shifted. This could be a strong long-term signal for wetter conditions in Arizona.

 Posted by at 10:19 pm

Where does the winter of 1992-1993 fit?

 Climate, Northern Arizona Weather, Pontification  Comments Off on Where does the winter of 1992-1993 fit?
Sep 192015
 

The start of next week may be very wet! Also, the 1 and 3-month outlooks are wet. Just so you know.

But, after posting a link on Facebook to Scientific American article (How This Year’s El Niño Compares with the Past), I got a challenging question from MN about the winter of 1992-1993. In deed, this was probably one of the wettest winters in the last 60ish years. In December of 1992, Flagstaff received 6.78 inches of liquid water precipitation. In January and February of 1993, Flagstaff received 9.55 and 10.05 inches of precipitation. Also, these months were part of a longer term wet period. In the 12 months before the end of February 1993, Flagstaff reached over 48 inches of water. That more than double our typical one year normal. This peak is clear in the chart below.

12-month and 2-year Flagstaff precipitation totals.

12-month and 2-year Flagstaff precipitation totals.

It looks like the winter of 1992-1993 must have been an El Niño year. In 3 months, about 27 inches of water. Must have been….

The winter of 1992-1993 was not a El Niño winter. But, it overwhelmingly surpassed the so-called Great El Niño of 1997-1998. It was about as close to La Nada, neither El Niño or La Niña, as it could get.

Maybe because of my recent readings, the Atlantic Multidecadal Oscillation (AMO) came to my mind. This is a very long-term change in Atlantic Ocean temperatures. I covered it a bit in my last post. With neutral Pacific conditions, perhaps the AMO was in the driver’s seat.

Atlantic Multidecadal Oscillation Index. (http://www.esrl.noaa.gov/psd/data/timeseries/AMO/)

Atlantic Multidecadal Oscillation Index. (http://www.esrl.noaa.gov/psd/data/timeseries/AMO/)

The AMO went from nearly positive to considerably negative in the time leading up to that winter. So, I think at least from a non-expert, looking at a couple of charts point-of-view, the Atlantic could have been an important factor in the winter of 1992-1993 for Flagstaff.

Also, notice that was the last hurrah for wet conditions. After that winter, the AMO started to switch to a persistent positive mode. From my last post, there is a linkage between positive AMO conditions and drier conditions for the American Southwest.

One more note. Many of the people who are my age and grew up in Flagstaff in the late 1960s through the early 1990s, have a profound impression of Flagstaff having been much wetter growing up. On the other hand, some of the people who grew up before that time frame, seem to remember a drier time that was more like today. Completely anecdotal, but interesting.

 Posted by at 12:02 pm

Another reason the drought could be ending

 Climate  Comments Off on Another reason the drought could be ending
Sep 112015
 

The Atlantic Hurricane season must be damaging advertising revenue for the major U.S. television news networks. Other than tropical systems forming, then quickly falling apart, there just hasn’t been any of the damage they crave to drive the revenue. No scary hurricanes, no viewers.

On a side note, there has been much recent background noise around why we are seeing fewer strong Atlantic storms. One piece of information I find very interesting comes from a tweet by Dr. Philip Klotzbach at the University of Colorado. He and his colleague, Dr. Gray, are world-renowned hurricane forecasters. Below is the picture he tweeted.

12-month running average of the Atlantic Multidecadal Oscillation. (Klotzbach and Gray, originally 2008, updated)
12-month running average of the Atlantic Multidecadal Oscillation (AMO). (Klotzbach and Gray, originally 2008, updated)

Notice that the AMO has dropped over the last couple years. In 2010, I wrote a pretty long post discussing the future forecast for the AMO to do this. A strong influence for that post was an article from the Proceedings of the National Academy of Sciences (Pacific and Atlantic Ocean influences on multidecadal drought frequency in the United States, McCabe, Palecki, Betancourt, March 23, 2004
vol. 101 no. 12, PNAS) From that paper, I included the next chart.

Drought frequency (in percent of years) for positive and negative regimes of the PDO and AMO. (A) Positive PDO, negative AMO. (B) Negative PDO, negative AMO. (C) Positive PDO, positive AMO. (D) Negative PDO, positive AMO. The red areas show a greater than 30 percent likelihood of a drought. The blue areas show a lesss than 20 percent chance of drought.

Drought frequency (in percent of years) for positive and negative regimes of the PDO and AMO. (A) Positive PDO, negative AMO. (B) Negative PDO, negative AMO. (C) Positive PDO, positive AMO. (D) Negative PDO, positive AMO. The red areas show a greater than 30 percent likelihood of a drought. The blue areas show a less than 20 percent chance of drought.

Notice that in A and B, the AMO is negative and Arizona is wetter, regardless of the state of the Pacific Decadal Oscillation (PDO). I found one quote from the PDO-AMO article particularly salient:

Although it is always prudent to be conservative about water resources, particularly in the semiarid West, it may be particularly necessary in the next decade.

The article is dated March of 2004. That decade has ended. The AMO has appeared to have shifted to a negative phase. And, our 12-month average precipitation has been on the rise. Also, Dr. Klotzbach’s shows roughly 1995 as the start of the positive AMO. This also coincides with the downfall in our precipitation. Are they linked? Is the drought ending?

12-month and 2-year Flagstaff precipitation totals.

12-month and 2-year Flagstaff precipitation totals from 1950 to August 2015.

This month should be wet according to the long-range forecasts. The next 6-8 months should be wet, too. We will see. The recent 6-10 and 8-14 day outlooks have bounced around like a super ball lately. I think this is mostly due to an active hurricane season in the Eastern Pacific Ocean. The GFS model continues to have significant wet periods for Arizona in the period out to 2 weeks.

 

 Posted by at 11:10 pm

Strong start to Monsoon Season on the way

 Climate, Monsoon, Northern Arizona Weather  Comments Off on Strong start to Monsoon Season on the way
Jun 252015
 

Recently, I noticed that the Wikipedia page on Monsoons wasn’t fond of referring to the North American Monsoon in the southwestern U.S. as a true monsoon.

Whether it is true or not, it looks like Flagstaff and most of Arizona will get a nice wet start to the season over the next week or so. Below is the 10-day precipitation outlook.

Ten day precipitation outlook from the GFS Model at the  Climate Prediction Center.

Ten day precipitation outlook from the GFS Model at the Climate Prediction Center.

 Posted by at 3:25 am
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