Aug 192013

According to the long-range outlooks and GFS model,  an intense low pressure system(now identified as 94E) will move up the west coast of Mexico and bring plenty of moisture next Sunday and Monday. It’s still a long ways out, but the GFS model and the 6-10 day outlook predict above average precipitation. It has been consistent for several model runs.

6-10 day precipitation outlook from the Climate Prediction Center. Monday Afternoon, August 19, 2013

6-10 day precipitation outlook from the Climate Prediction Center. Monday Afternoon, August 19, 2013

The last GFS model had the bulk of the precipitation falling in western Arizona. It’s not a sure bet, yet.

 Posted by at 5:41 pm
Aug 152013

With rain showers to the southwest of us, moisture has reentered Northern Arizona. The chance for rain increases over the next few days. The North American Mesoscale model shows a health precipitation amounts over the next 3 days. I was starting to wonder.

3-day precipitation forecast from the North American Mesoscale model. NCEP at the National Weather Service.

3-day precipitation forecast from the North American Mesoscale model. National Centers for Environmental Prediction at the National Weather Service.

 Posted by at 6:58 am
Jul 292013

I think we could go ahead and consider the 7.57 inches of precipitation we have received in the month of July an all time record for the month. I know it’s short of the 7.58 inches “Flagstaff” recorded in 1919. The National Weather Service office in Flagstaff has updated the monthly total with great graphics daily. Here is this morning’s update.

5 Wettest July in Flagstaff

5 Wettest July in Flagstaff

While we are 1/100th of an inch shy of the record, I’m not sure 1919 is a meaningful record to break. I have mentioned in the past that the weather record for Flagstaff isn’t as clean-cut as you might hope. The Flagstaff weather station has gotten around town. Personally, I think 1950 is the year that forms the basis of a real weather record for a single location. The text below is from a Climate of Flagstaff record provided by the National Weather Service.

The first official weather station in Flagstaff was established September 9, 1898. The 
office was located at the southeast corner of Aspen Avenue and Park Street in a one-
story five-room brick building known as the Milligan Cottage. The first observer was
Miss Elizabeth Renoe, who later married a young attorney who became the first United 
States Senator from Arizona, Senator Henry Ashurst. 
On March 15, 1912, the station was moved to Sitgreaves and Ellery Streets, which was 
one-half mile southeast of the previous location. The station remained at this location 
until October 29, 1919. The station was then moved to 602 North Leroux Street. 
On June 1, 1943, the weather station was moved to the Federal Post Office Building in 
downtown Flagstaff. A first-order weather station was then established. 
On January 12, 1950, the weather station was moved to the Flagstaff Municipal Airport,
six miles south of Flagstaff. The station and the weather office remained at the airport 
until June 1994 when the National Weather Service office moved to the Camp Navajo 
Army Depot in Bellemont, 10 miles west of Flagstaff. From July 1994 to July 1995, 
the National Weather Service office was temporarily located in the army barracks, 
while a new office was constructed. On July 21, 1995, the office officially moved to 
its current location on the Camp Navajo Army Depot. An automated weather station 
(ASOS) remains at the Flagstaff Municipal Airport recording the official observations
for Flagstaff. The ASOS was commissioned July 1, 1994. 

In the summer of 1919, The station was at the corner of Sitgreaves and Ellery. By connecting the current day Ellery and Sitgreaves, it appears their intersection would have been around the Prochnow Auditorium on the NAU campus. This would put it about three and a half miles from where it is at the airport now. The station has moved to Leroux street, then the Federal building, before going to the airport in 1950. We know that a few miles in monsoon seasons can make a large difference in precipitation received.

Month to date rainfall totals at

Month to date rainfall totals at

The image above is of monthly rainfall totals reported by people to A quick look shows that the monthly rainfall totals are variable by location. My site is about a mile from the down town locations and about 4.5 miles from the airport. I’m pretty confident that I haven’t missed a day. Also, I use both an electronic and a manual rain gauges. I have a had about 1 inch less rain than the airport. Most years, I seem to get more rain than the airport. How storms build and travel can cause wide swings in actual rainfall amounts. Because the station has moved around, and the location variability of precipitation amounts in the monsoon season. I don’t think the 1919 record is meaningful. I think we have set a new record which only dates back to 1950 and that is the meaningful record we have.

The problem I foresee is that we are drying out for the next few days. Even the small amount of rainfall needed to break the “record” may not fall. We will see.


 Posted by at 9:16 am
Jul 252013

Last night storm movement took on a southerly direction. As a result, a few storms treated Flagstaff residents to a strong lightning show with a good dose of rain. From looking at the radar images in the middle of the night, I think the southerly flow provided the lift over the San Francisco Peaks to generate storms. It was enough to push me past the 5 inch level for precipitation at my house this month. A quick look at the weather record for Flagstaff shows that only 1964 and 1986 had precipitation totals for July of more than 5 inches. But, will it last. In 1964, the following August was drier, and closer to normal. In 1986, August was wetter with about 8 inches.

The drying trend out in the future is looking more likely as we move forward. Early next week it looks like drier air will move into the Northern Arizona area. Even if the rains stopped now, we would be close to an average monsoon season for rainfall. Persistent moisture in the area is responsible. It will be interesting to see how wet or dry we are in August. Here is the Flagstaff dewpoint temperature history for this summer from the National Weather Service office in Tucson.

Monsoon daily dewpoint tracker for Flagstaff from the National Weather Service in Tucson

Monsoon daily dewpoint tracker for Flagstaff from the National Weather Service in Tucson

I don’t remember such a sustained, above average dewpoint history. The red is the average dewpoint temperatures for 1962-2010. I thinks is fairly rare that we are above 50F. Yes, it has been wet and potentially uncomfortable when warm.

TR reminded me that the connection between dewpoint and humidity isn’t in the forefront of people’s minds. The dewpoint temperature is the temperature below which dew will form. This temperature is dependent on the moisture content of the air. Humidity is the water content of the air compared to how much water vapor the air can hold. As air warms, it can hold more water vapor, so the humidity for a given dewpoint temperature actually drops. If our dew point temperature is 55F, we would have 100% humidity at an air temperature of 55F. At an air temperature of 75F and a dewpoint of 55F, our humidity would be 50%. High temperature, same amount of water equals lower humidity.

The bottom line is that it has felt more like the East Coast than Arizona lately because it so wet.



 Posted by at 7:07 am
Jul 162013

MN asked me a couple of times last week why I wasn’t logging my rain at I had been, but even with all the cloudiness last week, I received very little precipitation.

Today, much like a day or two last week, the forecast models and various forecasters are saying were have a high likelihood of thunderstorms with lots of precipitation. There is a nice amount of moisture in the air…actually, the air feels soaking wet. There are even a few lingering storms wandering about Arizona this morning. The problem is that for anything to get started in earnest, we need lift. We need a temperature differential. Or, some winds to cause lift over out mountains.

Last week, there was a persistent storm that formed from orographic lift over the peaks. From the Peaks northward, there was rain. Most of the rest of Northern Arizona saw little to no rain. The problem that day, and I think again today, is that while moisture was abundant, the sun was barely seen. Without warming of the surface air, it doesn’t start to lift due to its buoyancy. Hence, we see no condensation into cumulus and then cumulonimbus clouds.

It doesn’t look like we will have a strong front moving through, and unless things clear up, I don’t know what will drive anything significant today.

 Posted by at 6:57 am
Jun 292013

Our all-time record high is 97 degrees. Yesterday’s record of 96 for Flagstaff missed the record. Now, the forecast show Flagstaff being cooler than that over the next few days. This is due to the arrival of some monsoonal moisture which has brought clouds and thunder. Here are yesterday’s records.


 COTTONWOOD-TUZIGOOT (1977 - 2013)     114          110        IN  1994
 FLAGSTAFF (1899 - 2013)                96          94         IN  1990
 GRAND CANYON NP N RIM (1925 - 2013)    89          88         IN  1950
 PAGE (1997 - 2013)                    109          103        IN  2011
 PETRIFIED FOREST (1931 - 2013)        103          103 (TIED) IN  1990
 PRESCOTT (1898 - 2013)                104          102        IN  1900
 PRESCOTT AIRPORT (1948 - 2013)        104          100        IN  1990
 SELIGMAN (1905 - 2013)                105          103        IN  1970
 WINSLOW (1899 - 2013)                 107          104        IN  1973

If you haven’t visited the National Weather Service’s Monsoon Tracking site from Tucson, I think it is worth a look. Here is the Flagstaff dew point chart. Notice the boost the dewpoint temperature got yesterday. That dewpoint temperature boost turned the temperatures around as clouds formed. The outlook is for the monsoon to steadily build.

Flagstaff dewpoint graph from the NWS Monsoon tracking site

Flagstaff dewpoint graph from the NWS Monsoon tracking site

 Posted by at 7:04 am
Jun 272013

The National Weather Service has issued an Excessive Heat Warning at elevations below 4000 feet. Here is the official definition:


I think an “Excessive Heat Warning” is when TR sends you an IM telling you “it’s going to be really hot.” He’s right. The forecast for the next few days is hot. But, this is the time of year when it is hot.

Another friend of mine, JW always says it has to get hot for the monsoon season to really start. There is a linkage between the heat and the start of the summer rainy season. The heating in the deep southwest, especially around Yuma, forms a thermal low pressure zone. The counterclockwise flow around this low helps drive the moisture up from the south. More on this at my Monsoon Mechanics webpage.

I feel like the recent National Weather Service forecasts have overshot the temperatures we have actually seen. But, for the next few days, starting today, the record high temperatures are 96, 94, 94, 93, 92, 91, 92, 93, 96, 97, 96. I’m pretty sure the 97 is our all time record high and was in 1973. A few of those were in 1974 and a couple in 2007. So, the forecast definitely has us in the record range.  I’ll try to talk about the high temperatures after we get to the rains.

The start of the monsoon season continues to too wet. This particular outlook from the Climate Prediction Center has enthralled me. This is the drought outlook. Check out our area. This outlook has parts of Arizona coming out of drought by the end of the summer. Amazing! The North American Mesoscale model has showers starting tomorrow in Northern Arizona. This seems a bit early to me.

United States Seasonal Drought Outlook

United States Seasonal Drought Outlook

 Posted by at 4:46 am
Jun 212013

Update: The whole post is still good, but the Climate Prediction Center really stepped out today. I can’t remember an outlook like this for late June…ever! The 8-14 day and 30 day outlooks look very similar. Maybe we will have an early and wet monsoon season. I’m not ready to buy it, yet.

Latest 6 to 10 Day Precipitation Outlook from the Climate Prediction Center

Latest 6 to 10 Day Precipitation Outlook from the Climate Prediction Center


It’s that time of year. Last weekend, the rain that fell in Flagstaff was from a small front moving through the area, not. The regular southerly monsoon all flow. I thought it felt humid, and it did. We had a brief spike in our dew point temperatures with the system. But, the dew point temperatures have fallen back below normal.

Flagstaff's recent dew point temperatures

Flagstaff’s recent dew point temperatures.

A  dry southwesterly flow has brought us our very dry red flag conditions. My Monsoon Mechanics page shows the wind directions favorable to the start and maintenance of the monsoon all flow. We need winds out of the south to southeast. Luckily, the winds will shift after this weekend. The southwest flow should slow and the wind direction should swing counterclockwise. We will have to wait and see.

 Posted by at 4:59 pm  Tagged with:
Sep 082012

The National Weather Service has posted their Month In Review for August, 2012. The report includes the graphic below comparing August 2012 precipitation to historic numbers.

Comparison of precipitation for August 2012 to historic normal. National Weather Service - Flagstaff

Comparison of precipitation for August 2012 to historic normal. National Weather Service - Flagstaff

There are very wet areas. There are very dry areas. The Monsoon Season rarely results in uniform distribution of rainfall. I think looking at helps show this reality of the Monsoon Season. Looking across Northern Arizona, we see wide variability. I know I kept wondering if the weather station at the Flagstaff Airport had its rain gauge under a tree. They reported less than 3 inches while the eastern and northern areas of Flagstaff reported considerably more than 3 inches. It matches the division to the south and east in the image above.

If you look down around the Prescott-Sedona area, you can note several locations above 4 inches and several locations under two inches. one spot near Clarkdale had almost 6 inches. Another site near Prescott recorded only 1.1 inches. It's just how the Monsoon Season works.

For the next few days, most of Northern Arizona will be wetter than normal. If you have ever been to the Killer Whale Show at Seaworld, you already know the saying "you will get wet, you may get soaked." If you have a chance, buy a high quality rain gauge and report your rain at

August precipitation for Northern Arizona from

August precipitation for Northern Arizona from


 Posted by at 7:01 am
Aug 242012

The last few days have been wet. Many people had rain falls over 1 inch. Even the Weather Service reported almost an inch for yesterday. I might wander out to the airport this weekend to look at how they have positioned their rain gauge. High and low pressure areas are going to shift around for the next few days and dry us out. The dry conditions may be temporary or last quite a while. The Climate Prediction Center has 6-10 and 8-14 day outlooks for drier than average conditions for Arizona. Most forecasts, such as from and the National Weather Service, don’t quite reflect drier than average. Their predictions are for mostly 30-40% chance of precipitation. These forecast will probably change.

Today we should have drier weather.

Latest 8 to 14 Day Precipitation Outlook from the Climate Prediction Center

Latest 8 to 14 Day Precipitation Outlook from the Climate Prediction Center

 Posted by at 7:08 am
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