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

Another long break and a long delay to monsoonal flow to Flagstaff

 El Nino/La Nina, Lake Powell, Models, Monsoon, Northern Arizona Weather, Outlooks  Comments Off on Another long break and a long delay to monsoonal flow to Flagstaff
Jun 242017
 
The Partheonon at night, May 2017.

Yes, my last post was on May 4. Here we are several weeks, and European trips, later. Since May 4th, I have travelled to Prague, Greece, Italy, Austria and the far south of Germany. Prague was a work trip to see some stunning work presented! Greece was a week long sailing trip that came about because of the 40th birthday parties of a couple friends. Athens is truly striking! Italy was for a long weekend by the Gardasee (Lake Garda). Austria is in between, and with beautiful springtime green meadows against the rocky Alps. Ah! And now the weather!

The Partheonon at night, May 2017.

The Parthenon at night, May 2017.

Of course it’s fire season. I’m surprised by the number of fires and the intensity of the fire near Brian’s Head. It’s been a fairly wet winter and spring for most of the southwest. One of the indicators of this is the meteoric rise in Lake Powell. It is the deepest it has been on this date since 2011. It could be the second deepest summer out of the last decade. The lake hit it’s low point, just shy of 3594 feet in early spring. Currently, it is around the elevation of 3633 and still rising several inches per day. A wet year so far.

Lake Powell water level from water-data.com

Lake Powell water level from water-data.com. Notice it’s more like the last 5 years.

Now, the monsoon season. I realize there have been several faux monsoon storms. They were more driven by frontal systems passing to the north of Arizona, than a sustained moist flow from the south. The good news is that the heat has arrive to start the monsoon engine. Joe D’Aleo has written a nice summary of how the heat drives the flow. You can also take a look at my Monsoon Mechanics page.

The less good news is that the current computer forecasts point to the flow starting very much to the east of Flagstaff. It maybe after the 4th of July before the rains start in earnest. Below is a recent GFS model out look for precipitation between now and July 4. You can see only a small amount of precipitation predicted during this time frame.

Precipitation outlook between now and July 4, 2017 from the GFS model on TropicalTidbits.com

Precipitation outlook between now and July 4, 2017 from the GFS model on TropicalTidbits.com

Back to the better news, the outlook for the development of El Nino is low. El Nino conditions include the development of anomalous winds that can cut across the moisture flow, sending it elsewhere. Hopefully, when the season starts it will be a normal one.

Oh wait, what is a normal monsoon season?

 Posted by at 4:21 am
Feb 192016
 

Warm and dry has become the February story. The wet cold start has faded into sun and occasional high winds. There have be a few times the outlook was positive for wet conditions. It hasn’t happened.

Is it unusual for February to be dry during an El Niño winter. I think the data are pretty messy and there really isn’t enough to be very meaningful. Since 1950, the average for February precipitation in Flagstaff is about 2 inches. There are very wet and fairly dry Februaries during El Niño years.

Most of the areas that normally benefit from El Niños are benefiting this year. We continue to be way ahead on 12 and 24 month total precipitation.

The GFS model shows a possible weak storm at the end of the month, and a stronger storm at the start of March.

12-hour precipiation outlook ending noon, March 4, 2016. (Tropical Tidbits website.)

12-hour precipiation outlook ending noon, March 4, 2016. (Tropical Tidbits website.)

The 3 month outlook from the Climate Prediction Center continues to look positive from a precipitation point of view.

3-month precipitation outlook from the Climate Prediction Center.

3-month precipitation outlook from the Climate Prediction Center.

There is still time left this winter for more snow. March is typically the wettest month of the year. I think more is on the way.

 Posted by at 4:50 pm

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
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

Model predicts typical start to Monsoon Season

 El Nino/La Nina, Models, Monsoon, Outlooks  Comments Off on Model predicts typical start to Monsoon Season
Jun 212015
 

I think I mentioned several times last summer NOAA’s GFS model predictions of the monsoon season impressed me.They seemed remarkable accurate. I say seemed, because I don’t think I ever did or saw any statistical analysis to prove it. We will see how they do this year.

For now, the model has the season walking slowly up to the season. If you remember last summer it started in earnest. This year, I think we will start to some thunderstorm action at the end of this week, but probably not the real start until closer to the 4th of July. This is normal.

The current El Nino conditions and the warm blob off the coast of California continue to cause me some concern. The image below is the most recent global sea surface anomaly picture from NOAA. There is plenty of warm water to generate the moisture needed for a strong monsoon season. I still worry that jet stream winds might not cooperate One of the reasons there are few strong Atlantic hurricanes in El Nino conditions is due to the high level winds that shear the tops of the clouds off as storms develop in the Atlantic or the Gulf of Mexico. Could these winds impede our monsoon season?

I don’t know. Also, I don’t think there is any clear data on any effect from El Ninos on monsoon precipitation. We will have to wait and see. For now, enjoy summer. The warm temperatures may not last long.

Global sea surfce temperature anomaly, June 18, 2015. (NOAA)

Global sea surfce temperature anomaly, June 18, 2015. (NOAA)

 Posted by at 5:47 am

Closer to normal June weather on the way

 Climate, El Nino/La Nina, Monsoon, Northern Arizona Weather, Outlooks  Comments Off on Closer to normal June weather on the way
Jun 142015
 

Through Sunday morning, we have received 1.14 inches of rainfall in June. This is a whopping inch over normal. While that is large rainfall for June, 1955 and 1956 are still well in the lead at 2.92 and 2.79. This is for the record since 1950. We could still beat these amounts depending on how the end of the month goes.

The next week or so isn’t going to help. Get ready for typical June weather. Sunny, warm days dominate the model outlook for the next week to 10 days. In Weather Underground’s outlook does not predict the dew point to drop much below 20. or fire conditions.

After 10 days, it’s hard to tell exactly what will happen. It looks like the annual moisture surge from the south will begin. There is plenty of warm water for drawing moisture. The Western Pacific Blob is remaining in place off the California Coast. El Nino conditions continue to strength around the Equator. If we can obtain and maintain the monsoon pattern we could have a wet season.

 Posted by at 9:47 pm

Running behind on winter

 El Nino/La Nina, Outlooks  Comments Off on Running behind on winter
Nov 102014
 

I usually shoot for the end of September to write my first post for the winter. Historically, this is because Arizona Snowbowl was dependent on natural snow. Now, they make their own snow. As a result, making the early decision about buying a season pass at a discount doesn’t matter so much.

As early as last spring, the media started to hype an oncoming “Monster El Nino.” A body of warm water moved across the Pacific Ocean from west to east, deep below the surface. To many it looked like a sure bet that this would be the first of many such warming events. I watched and waited.

There are two key components to having a successful El Nino. First, you need the warmer than normal water in the equatorial Pacific. Second, you need the equatorial trade winds to shift from their normal westerly direction to the east. The equatorial waters did warm. The trade winds did not shift. I’m going to go a bit deeper. If you want to go much deeper I strongly recommend Bob Tisdale’s 2014-2015 El Nino Series. He goes into deep detail and you can watch the entire evolution. I am going to use Anthony Watt’s ENSO Page at WattsUpWithThat site for a data source. He has collected a great deal of data from around the world that is difficult to find.

The equatorial Pacific has warmed. Occasionally, it has warmed above the El Nino threshold of 0.5 degrees above normal in the ENSO 3.4 region. The map below shows this region.

El Nino regions

El Nino regions

The warm water did arrive over the summer. The 3.4 region temperature anomaly did turn positive. The graph below from the Australian Bureau of Meteorology shows the anomaly. Over the summer, the anomaly barely crossed above the half degree line. It then fell almost all the way back to zero.

Niño 3.4 Region Sea Surface Temperature Index - 5 Years

Niño 3.4 Region Sea Surface Temperature Index – 5 Years

The problem causing the fall was that the trade winds did not reverse to support full El Nino conditions. As summer went on, more warm water arrived and the temperature trend reversed again.

Australia’s Bureau of Meteorology (BOM) monitors the difference in surface air pressure between Darwin, Australia and Tahiti. From this data, they calculate the Southern Oscillation Index (SOI). The pressure difference is indicative of which direction the winds are blowing. A negative value of the SOI indicates that the winds have shifted to support El Nino conditions. The threshold for El Nino conditions is -8. A graph below shows the SOI over the last 5 years. In the last 3 months shown, the SOI has been negative and at least close to -8. (August -11.4, September -7.5, October -8)

Graph of the Southern Oscillation Index

Southern Oscillation Index from the Australian Bureau of Meteorology.

It looks like the winds may have finally shifted. The sea surface temperatures are shifting. But, is it sustainable. Keep in mind that El Nino means the boy, and refers to the Christmas celebration of Jesus Christ’s birth. The warm waters would be recognized around Christmas time. There is another body of warm water transiting beneath the surface of the Pacific. This should arrive before Christmas. It could be the icing on the El Nino cake. Before you get your hopes too high, most of the outlooks are for weak El Nino conditions at best.

 Posted by at 7:08 am

Plenty of warm water

 Climate, El Nino/La Nina, Monsoon, Northern Arizona Weather  Comments Off on Plenty of warm water
Aug 112014
 

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

Global sea surface temperature anomaly, August 10, 2014. (National Centers for Environmental Prediction)

 Posted by at 6:49 am

Is the monsoon season over?

 El Nino/La Nina, Models, Monsoon, Outlooks  Comments Off on Is the monsoon season over?
Jul 152014
 

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)

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)

8-14 day precipitation outlook from the Climate Prediction Center. (14 July 2014)

 Posted by at 6:33 am
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