Nov 252014
 

I laugh quietly to myself with that headline. It’s not even Thanksgiving. And Thanksgiving will be beautiful. We have a bit of time before we should expect snow. But only a bit. I wonder what price we will pay for a beautiful Thanksgiving?

I don’t think we will have a foot of snow next week. But it might be pretty close. A large, strong Alaskan storm system will drop south to the California coast, then take off towards the east. The NoGAPs image below shows the storm drawing plenty of tropical moisture towards Arizona. All of the forecasting websites I check are very well aligned around a storm next week. For now, I think accumulations will stay below a foot of snow for most of Northern Arizona. Depending on temperatures, we may start with rain. Keep in mind, it is still over a week away. Everything can change, but the current alignment is remarkable.

This storm is right on plan with the new 1 and 3 month precipitation outlooks from the Climate Prediction Center shown below. I think we are a bit beyond whether this winter will be an El Nino winter or not. These outlooks predict above average precipitation for us.

Eastern Pacific precipitation outlook for Tuesday Morning, December 2, 2014

Eastern Pacific precipitation outlook for Tuesday Morning, December 2, 2014

One month precipitation outlook from the Climate Predication Center. November 20, 2014

One month precipitation outlook from the Climate Predication Center. November 20, 2014

Three month precipitation outlook from the Climate Prediction Center. (November 20, 2014)

Three month precipitation outlook from the Climate Prediction Center. (November 20, 2014)

 Posted by at 6:44 am
Nov 132014
 

Or, will we see rain Friday night.

Over the last week, the homegrown forecast at Wunderground.com has included a 30-40% chance of rain for Friday. No place else has been as consistent. All of the computer models(GFS, NoGAPs, NAM) have not shown rain until today. I can not remember another time where this has been the case. Yesterday, the National Weather Service predicted a 10% chance. This morning they have accelerated that to 30%.

So, we will see. Did Wunderground get it right? Are they ahead of the pack?

 Posted by at 6:35 am
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
Sep 302014
 

I’ve struggled the last few days with a broken internet connection, malfunctioning iPhone and a rainy weekend. The weekend struggle was the wonderful malaise that can hit Arizonans when it rains all day. Nonetheless, the Climate Prediction Center issued new outlooks for October and the 3-month period October to December.

The outlooks point to El Nino developing. I’m still not sure this is a reasonable expectation. Last spring and early summer, the sea surface temperatures in the Pacific Ocean near the equator appeared headed for a strong El Nino. Unfortunately, the trade-winds did not shift to support it and the sea surface temperatures fell. There is another burst of warm water headed towards Peru now. If the winds shift, we will have El Nino conditions and a high likelihood of a wet winter. If they don’t shift, we will see La Nada neutral conditions(I think this is what will happen). Here is NOAA’s narrative about the outlooks:

CURRENT ATMOSPHERIC AND OCEANIC OBSERVATIONS ARE CONSISTENT WITH ENSO-NEUTRAL 
CONDITIONS WITH THE LIKELY TRANSITION TO EL NINO CONDITIONS IN AUTUMN AND 
WINTER. A WEAK EL NINO EVENT IS MOST PROBABLE, HOWEVER THERE IS A CHANCE OF 
EITHER A MODERATE EVENT OR CONTINUED ENSO-NEUTRAL CONDITIONS INTO WINTER. A 
STRONG EL NINO EVENT IS NOT LIKELY TO OCCUR THIS YEAR. MOST DYNAMICAL AND 
STATISTICAL MODEL FORECASTS OF EAST-CENTRAL EQUATORIAL PACIFIC SEA SURFACE 
TEMPERATURES (SSTS) IN THE NINO 3.4 REGION (170W TO 120W LONGITUDE AND 5S TO 5N 
LATITUDE) INDICATE A WEAK EL NINO (+0.5C TO +0.9C) WITH PEAK ANOMALIES IN THE 
EARLY WINTER.

 

Here are the outlooks:

One-month precipitation outlook for October 2014 from the Climate Prediction Center

One-month precipitation outlook for October 2014 from the Climate Prediction Center

Three-month precipitation outlook for October- December 2014  from the Climate Predicction Center.

Three-month precipitation outlook for October- December 2014 from the Climate Prediction Center.

 Posted by at 7:10 am
Sep 162014
 

I have zoomed in and cropped the image below. There is still a pronounced boundary to the heavy precipitation area. The precipitation scale is the same as in the earlier image in my last post. This is from a shorter range, high-resolution model. I think Flagstaff ends up in the 3/4 to 1 inch range. Notice that another boundary is forming along I-40 to the east. Stay tuned! There will be areas of Arizona receiving large amounts of precipitation over the next few days.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

Cropped 72-hour total precipitation forecast from the North American Mesoscale computer model by the National Centers for Environmental Prediction. 16 September, 2014.

 Posted by at 6:49 am
Aug 232014
 

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)

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)

3-month precipitation outlook for September-November 2014. (from the Climate Prediction Center)

 Posted by at 7:03 am
Aug 172014
 

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.

 Posted by at 10:16 pm
Aug 132014
 

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.

 Posted by at 6:13 am
Jul 182014
 

This morning the Climate Prediction Center issued a new 90-day precipitation outlook. All of Arizona is in the above average precipitation zone.

Three-month precipitation outlook from the Climate Prediction Center.

Three-month precipitation outlook from the Climate Prediction Center.

 Posted by at 7:14 am
Jul 162014
 

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. From the National Center for Atmospheric Research.

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.

Dew point temperature outlook for midday Monday, 21 July 2014. From the National Center for Atmospheric Research.

 Posted by at 6:33 am
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