Aug 252010
 

This summer’s monsoon season has been one of the wettest on record. Yesterday’s public information statement  from the National Weather Service in Flagstaff give the details below. We aren’t quite done, yet. The rest of this week is looking similar to the first part of the week. Then, yet another wet weekend is in store for us. However, next weekend is looking fairly dry. The longer range GFS computer model is showing additional chances for precipitation in the distant future.

PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE FLAGSTAFF AZ 940 AM TUE AUG 24 2010

…NORTHERN ARIZONA`S WET MONSOON SEASON CONTNIUES…

YESTERDAY`S RAINFALL OF 1.15 INCHES MEASURED AT FLAGSTAFF`S PULLIAM AIRPORT MARKS THE FIFTH OCCURANCE OF AN INCH OR GREATER DAILY RAINFALL THIS SUMMER. ONLY ONE OTHER SUMMER HAS EXCEEDED THIS YEARS FREQUENCY OF 1 INCH OR GREATER DAILY RAINFALL DAYS, WHICH WAS 1986, WHEN SIX DAILY OCCURANCES OF AN INCH OR GREATER WERE OBSERVED.

ADDITIONALLY, THE ACCUMULATED RAINFALL SO FAR THIS MONSOON SEASON (WHICH OFFICIALLY BEGAN JUNE 15TH) HAS MEASURED 9.54 INCHES AS OF AUGUST 24TH, MAKING THE 2010 MONSOON SEASON THE 4TH WETTEST TO DATE SINCE RECORD KEEPING BEGAN.

WETTEST MONSOONS

(JUNE 15TH – AUGUST 24TH)

1. 14.25 – 1986

2. 10.33 – 1919

3. 9.97    - 1904

4. 9.54    - 2010

5. 9.24    - 1908

THE NORMAL PRECIPITATION TOTAL FOR JUNE-AUGUST IN FLAGSTAFF IS 5.09, AND WITH THE 9.54 INCHES COLLECTED SO FAR, WE`RE RUNNING AT 187% OF NORMAL. THUNDERSTORM CHANCES CONTINUE THIS WEEK SO STAY TUNED TO SEE IF FLAGSTAFF REACHES ANY HIGHER INTO THE TOP 5 WETTEST MONSOONS.

 Posted by at 6:35 am
Aug 092010
 

This might take a couple posts to actually get through the whole picture. It seems like there are 2 dominate issues and maybe a couple minor issues that are going to guide our fall and winter.

I’m a big believer that hurricanes can effect our weather via two mechanisms. First, they can deliver moisture to across Mexico from the Gulf of Mexico and the Caribbean Sea to our doorstep. This can cause precipitation to amounts to be higher than average. Second, they can actually disrupt the tropical moisture flow and locations of dominant high pressure systems. They can actually draw the moisture from thousands of miles around, drying out Northern Arizona. One of the big contributors to hurricane formation is the water temperatures in the Caribbean and Gulf of Mexico. La Nina’s are typically more favorable for active hurricane seasons. El Nino’s tend to generate a strong flow in the opposite direction of the normal hurricane paths, preventing hurricane development.

This Atlantic Hurricane Season is forecasted to be fairly strong with 14-20 named storms and 8-12 hurricanes (Climate Predictionn Center Hurricane Outlook 8-5-2010). This outlook was just updated. Although the season has started slowly, August to October are the peak months. There is still time for a strong season.

So, La Nina and El Nino can alter weather patterns significantly. El Nino in the fall and winter usually means wetter conditions. Last winter, an El Nino episode provided us with nearly 6 feet of snow in one week. Currently, the Pacific Ocean is building a La Nina episode. It just recently started to develop and forecasts vary as to how deep it will be. When looking at La Nina’s as an input to the precipitation outcome for the August-October time frame, There have been 7 La Nina’s through these months in the last 25 years, 1985, 1988, 1995, 1998, 1999, 2000, 2007. It’s arguable that 2000 was not a La Nina, but I have included it because the region was cold and clearly met the La Nina definition (El Nino Sea Surface temperature anomaly <-0.5) on either side of August-October.

Year La Nina SST Anomaly
1985 -0.5
1988 -1.3
1995 -0.5
1998 -1
1999 -1
2000 -0.4
2007 -1

In 1995 and 2007, the La Nina’s were just starting around the mid to late summer time period. For this year, the outlook for the August-October time frame is between -0.5 and about -1.25. Again, this could match either 1995 or 2007. Notice a theme here? Don’t get too bent on 1995 and 2007 being good predictors quite yet.

Summary of ENSO Model Forecasts

Summary of ENSO Model Forecasts

Another interesting sea surface temperature anomaly to track is the Pacific Decadal Oscillation. It’s a broader, longer term look at the Pacific and how it behaves. It has been negative for most of the last 3 years. With El Nino ending, it returned to negative in June. This is expected to last, and intensify for quite sometime. We can assume it will be negative for the next 6 months. How do the other years look?

Year PDO
1985 0.51
1988 -0.09
1995 0.61
1998 -0.94
1999 -1.57
2000 -1.24
2007 -0.44

1985 amd 1995 were both positive. But, 2007 and 1998 were negative.

Now, the hurricane picture in those La Nina years is interesting, too.

Year Atlantic Hurricanes Atlantic Tropical Storms Gulf Hurricanes Gulf Tropical Storms
1985 7 3 4 5
1988 5 12 3 5
1995 11 19 4 6
1998 10 14 2 5
1999 8 12 1 2
2000 8 15 2 4
2007 6 15 2 4

Remember, 14-20 named storms and 8-12 hurricanes are in the outlook. In this chart, tropical storms are equivalent to named storms. 1995 continues to be a potential match for this year. 2007 falls short on the total number of hurricanes, but is in the zone for total named storms. 1998 and 2000 are in the zone as well. The numbers of Gulf Storms are higher in many of the earlier years. But, 2007 still had 4 named storms in the Gulf of Mexico.

Here is where the real conundrum kicks in. When you take all of this data and add Flagstaff’s August to October precipitation to the chart you get this:

Year Flagstaff Precipitation La Nina SST Anomaly PDO Atlantic Hurricanes Atlantic Tropical Storms Gulf Hurricanes Gulf Tropical Storms
1985 7.15 -0.5 0.51 7 3 4 1
1988 6.15 -1.3 -0.09 5 12 3 2
1995 3.88 -0.5 0.61 11 19 4 2
1998 10.38 -1 -0.94 10 14 2 3
1999 6.99 -1 -1.57 8 12 1 1
2000 7.04 -0.4 -1.24 8 15 2 2
2007 5.84 -1 -0.44 6 15 2 2

The average precipitation for the August to October time periods in all these La Nina years is 6.78 inches, with a standard deviation of  1.95 inches. This put 1995 and 1998 at opposite ends of the spectrum and outside one standard deviation of the average. The positive PDO in 1995 with a La Nina, and an active hurricane season seems to point to a dry period.

To me, this seems to me to indicate that 2007, and maybe 1998, could be the best analogs for this year. A couple caveats about 1998. La Nina started just a couple months earlier than this year. It also followed a strong El Nino, in fact the strongest.

So, I am going to pick 1998 as the analog year for my forecast. Which would mean that we should see greater than average precipitation(1984-2009 average is 7.61 inches) for these months. In 1998, Flagstaff received 3.32 inches in August, 4.76 in September and 2.96 in October. I think we will repeat a wetter than average trend similar to this, not 1995′s very dry trend or 2007 average trend.

But what about winter? La Nina means drier…or does it?

 Posted by at 4:40 am
Jul 312010
 

Wow! Yesterday morning, the rain we had was simply delightful. Watching it gently fall with a cup of coffee in my hand was great.

Yesterday afternoon, the town was shutdown with a massive torrential rainfall. 89A, Milton at the railroad bridge, and Soliere were all flooded and closed. Other minor side streets had similar issues. It took my daughter over an hour to go 3 miles to work last night. Here is a great image and story from the Arizona Daily Sun.

Milton Flooding - Arizona Daily Sun

Milton Flooding - Arizona Daily Sun

It was a record rainfall day for the airport.

PRECIPITATION (IN)
  YESTERDAY        1.33R         1.33 2010   0.10   1.23      T
  MONTH TO DATE    5.64                      2.30   3.34     1.00
  SINCE SEP 1     19.83                     19.92  -0.09    12.56
  SINCE JAN 1     15.12                     12.18   2.94     6.20

Notice that even with last fall and last spring being very dry, the wet winter and summer have boosted us to normal precipitation levels since last September. Here is the radar estimation of precipitation from yesterday (Intellicast.com)

24 Rainfall estimate - Intellicast.com (will update with time)

24 Rainfall estimate - Intellicast.com (will update with time)

The current trend is to last through the weekend. Next week should be more like the standard monsoon pattern.

 Posted by at 6:49 am
Jul 172010
 

Did not really see the big storm coming yesterday. I thought things would hold off until today, Saturday. This should be the weather pattern for the weekend. Dewpoints have remained high. There is plenty of precipitable water. Watch-out for flash flooding.

Check this out. A record high and a record low within a few hundred miles of each other? Must be monsoon season.

Record Report


000
SXUS75 KFGZ 170155
RERFGZ

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
600 PM MST FRI JUL 16 2010


...RECORD HIGH LOW TEMPERATURES FOR NORTHERN ARIZONA ON JUL 16 2010...


CITY (PERIOD OF RECORD)         NEW HIGH LOW     PREVIOUS RECORD/YEAR
HEBER RS (1951 - 2010)                 66          65         IN  1963
PRESCOTT (1898 - 2010)                 71          70         IN  1970


...RECORD HIGH TEMPERATURES FOR NORTHERN ARIZONA ON JUL 16 2010...

CITY (PERIOD OF RECORD)            NEW HIGH      PREVIOUS RECORD/YEAR
PAGE (1958 - 2010)                    106          104        IN  2006


...RECORD LOW TEMPERATURES FOR NORTHERN ARIZONA ON JUL 16 2010...


CITY (PERIOD OF RECORD)            NEW LOW       PREVIOUS RECORD/YEAR
PETRIFIED FOREST (1931 - 2010)         50          52         IN  1935



THESE RECORDS ARE PRELIMINARY PENDING OFFICIAL REPORTS.
 Posted by at 5:18 am
Jul 112010
 

My weather station logged 0.29 inches on Sunday, as a couple thunderstorm waves moved over Flagstaff. Not every place logged as much.

Flagstaff Dewpoint - SUmmer 2010

Flagstaff Dewpoint - SUmmer 2010

Monday will maintain higher dewpoints and good chances for thunderstorms. But, as we go into the week, we will see dryer air move back into the area. Of course, this means lower chances for thunderstorms. They should still be possible.

It’s interesting to note that Los Angeles is still in the “June Gloom” mode. This is fairly late in the season for cooler temperatures and gloomy conditions. They set a record for a low, daily maximum temperatures. I am wondering what the meaning of this and high heat on the East Coast and in Central Europe are to our summer monsoon outlook.

 Posted by at 9:25 pm
Jul 052010
 

Well, the 4th of July came and went without the slightest hint of a thunderstorm. This is notable. Seems like  July 4th’s bring precipitation to the Northland.This pattern should shift this week. For the next couple of days, high pressure to the southwest of us, which has crept in from the west, will dominate and continue to bring us southwest winds. The flow will shift later in the week as low pressure builds to the southwest of us. This sets up the typical monsoonal flow. By next weekend, the moisture should return, with thunderstorms building.

The Arizona Daily Sun has a front page article about our notable weather last year. As a reminder, the dry monsoon season last summer was due to El Nino. El Nino repositioned the high pressure over us and prevented the monsonal moisture flow.Wildly clear skies resulted in our above average temperatures and no cooling from daily cloud development. El Nino was also responsible for our major snow falls. But, El Nino you typically bring a warmer pattern for the winter. This was clearly not the case.

 Posted by at 7:35 am
Jun 142010
 

Looks like most of Flagstaff avoided freezing temperatures this weekend. But, some outlying areas, like Bellemont and Fort Valley. KAZFLAGS29, a personal weather station at in the Fort Valley(Baderville?) area recorded a low of 27F yesterday morning. The weather service in Bellemont reported a low of 27F.

It’s always odd to see a record breaking hot weekend followed by record breaking cold the next weekend, or vice versa. Record cold temperatures and record low high temperatures were recorded over the weekend.

Things are looking up from here. Next weekend will hopefully be a near perfect June weekend.

 Posted by at 6:39 am
Mar 162010
 

Here is the winter temperature summary from the National Climatic Data Center:

Winter Temperatures 2009-2010

Winter Temperatures 2009-2010

Keep in mind this doesn’t include offsets for things like Urban Heat Island(UHI) effect. Many believe that UHI will prevent many locations from ever breaking record lows. But, the low temperatures certainly explain why the snow is still around. And, how Flagstaff managed to break the record for longest time period with more than 8  inches of snow on the ground.

With the fairly strong El Nino, we were able to collect the precipitation in the first place:

Winter 2010 Precipitation

Winter 2010 Precipitation

 Posted by at 12:51 pm
Mar 122010
 

Once again, the nice weather is just around the corner. Next week should be mostly nice, sunny and warm. But, we have one more small storm that is going to try and make it to Northern Arizona on Saturday Night and Sunday. It will bring only small amounts of precipitation with a high snow level, compared to recent storms.

On the topic of snow fall this year, this chart speaks for itself:

 Posted by at 6:38 am
Mar 082010
 

As late as last evening about 8pm, it still looked like we would get 4-8 more inches. For Flagstaff it never materialized. But, don’t worry, today could bring some widely scattered snow, more looks to be on the way for tomorrow. The storm did hold temperatures very constant. Here is an interesting record report:

... Record high low temperatures for northern Arizona on Mar 07 2010...
City (period of record) new high low previous record/year
Cottonwood-tuzigoot (1977 - 2010) 44 44 (tied) in 2001

... Record low high temperatures for northern Arizona on Mar 07 2010...
City (period of record) new low high previous record/year
Cottonwood-tuzigoot (1977 - 2010) 49 50 in 1981

Temperatures just didn’t change much yesterday. I can’t remember seeing this happen before.

While we didn’t end up with piles of snow yesterday, we did set a new precipitation record:

...THE FLAGSTAFF AZ AIRPORT CLIMATE SUMMARY FOR MARCH 7 2010...

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1898 TO 2010

WEATHER ITEM   OBSERVED TIME   RECORD YEAR NORMAL DEPARTURE LAST
                VALUE   (LST)  VALUE       VALUE  FROM      YEAR
                                                  NORMAL
..................................................................
TEMPERATURE (F)
 YESTERDAY
  MAXIMUM         35   1133 AM  66    1972  48    -13       42
                                      1910
  MINIMUM         27   1159 PM  -1    1945  22      5       19
  AVERAGE         31                        35     -4       31

PRECIPITATION (IN)
  YESTERDAY        0.53R         0.52 1918   0.09   0.44      T
  MONTH TO DATE    0.81                      0.67   0.14      T
  SINCE SEP 1     12.79                     13.15  -0.36     8.57
  SINCE JAN 1      8.08                      5.41   2.67     2.21

SNOWFALL (IN)
  YESTERDAY        5.1           7.6  2000   0.8    4.3       T
  MONTH TO DATE    7.1                       5.9    1.2       T
  SINCE SEP 1    129.0                      83.8   45.2     80.7
  SINCE JUL 1    129.0                      83.8   45.2     80.7
  SNOW DEPTH      15

 Posted by at 6:32 am
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