Yet again, the computers can’t make up their minds

 Northern Arizona Weather  Comments Off on Yet again, the computers can’t make up their minds
Feb 242017
 
US Navy NAVGEM computer model forecast of precipitation rate for Monday night, February 27, 2017. (from Tropical Tidbits)

Maybe one computer has made up it’s mind. The Navy computer model is predicting a wet end to the February on a consistent basis. NOAA’s GFS model is not repeatably predicting anything. On Friday, two runs of the GFS model shows very light precipitation through the end of the month. Then, there were two other runs that showed over an inch of water coming to the Flagstaff are by the end of the month. Given the recent misses in forecast heavy rain or snow for Arizona, I am doubtful we will see a big storm for the start of next week.

If the most recent runs are accurate, there could be significant snowfall by next Wednesday. A little snow or rain could fall during the day on Sunday. Then, Monday afternoon through Tuesday night, Flagstaff could receive 8-12 inches of snow. So, be ready.

February has been warm and dry. It probably won’t be the warmest or driest since 1950, but it will be in the top 5 warm Februaries since 1950. If the precipitation comes through, there is still a chance to be at the average for the month. I’m doubtful.

US Navy NAVGEM computer model forecast of precipitation rate for Monday night, February 27, 2017. (from Tropical Tidbits)

US Navy NAVGEM computer model forecast of precipitation rate for Monday night, February 27, 2017. (from Tropical Tidbits)

 

 Posted by at 11:43 pm

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

Wetter ab dem Wochenende: Die Wettermodelle sind sich überhaupt nicht einig

 Models, Northern Arizona Weather, Winter Storms  Comments Off on Wetter ab dem Wochenende: Die Wettermodelle sind sich überhaupt nicht einig
Feb 152017
 

Reader: Stu, that title is in German.

Stu: I know, but it will make sense later on.

Bis Freitag scheinen sich die Wettermodelle noch sehr einig zu sein, was am Wetterhimmel passiert. Aber schon am Wochenende sind sie sich schon nicht mehr einig, die Temperaturspanne wird breiter. Und in der nächsten Woche liegen die Prognosen derzeit sogar 20 Grad auseinander. Das Wetter weiß noch nicht, wohin die Reise geht. Winter oder Frühling? Beides ist noch möglich. (wetter.de)

The computer models have been crazy with changes lately. As I read this brief story yesterday on wetter.de, it appeared very relevant to me. The computer models for the Southwestern US have been subjects to wild swings when predicting precipitation for the rest of the month, let alone this weekend.  According to this brief article, there is a 20 degree C difference between computer model runs. That means it could be sunny and 68 degree F on Saturday, or it could be freezing. I’m hoping for warm, and we are heading to Bamberg to test drive smoked beer.

This weekend will be wet, and the rain and possible snow will continue through Tuesday. Snow levels will start high, but drop through this time. Snowbowl should get a nice recharge. Somewhere between 1 and 2 inches of precipitation will probably fall between now and the middle of next week.

If you go to Google translate, you can copy and past the German text above and get a rough translation.

 Posted by at 11:17 pm

Rest of February looks wetter than on Friday

 Models, Northern Arizona Weather, Outlooks  Comments Off on Rest of February looks wetter than on Friday
Feb 122017
 
Total precipitation forecast from the GFS model through Sunday afternoon, February 26. (from TropicalTidbits.com on Sunday February 12, 2017))

The computer GFS computer model has been changing the precipitation outlook for the rest of the month quite a bit between runs. On Friday, the rest of the month, through Sunday evening, February 26, looked fairly wet. This image is reposted below.Flagstaff was in the 1.5 to 2 inch range.

Total precipitation forecast through Sunday evening February 26, 2017 from the GFS model. (from TropicalTidbits.com on February 10, 2017)

Total precipitation forecast through Sunday evening February 26, 2017 from the GFS model. (from TropicalTidbits.com on February 10, 2017)

This Sunday morning, everything looks remarkably wetter!!! Flagstaff is in the 3-4 inch, if not more, range. The series of storms for the rest of the month, including the current one, are proving very tricky for the model. Similar effects are showing up in the navy model. Still, the snow levels are projected to remain high for a while. A little snow could fall on Wednesday, and next weekend.

Total precipitation forecast from the GFS model through Sunday afternoon, February 26. (from TropicalTidbits.com on Sunday February 12, 2017))

Total precipitation forecast from the GFS model through Sunday afternoon, February 26. (from TropicalTidbits.com on Sunday February 12, 2017))

 Posted by at 8:22 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

Two wet weekends ahead

 Northern Arizona Weather, Winter Storms  Comments Off on Two wet weekends ahead
Feb 082017
 
US Navy NAVGEM model for precipitation rates, Saturday evening, February 12, 2017. (from Tropical Tidbits)

The pattern for the rest of February is looking similar to the holidays. Very unstable and hard to predict, but with a few chances for significant rain and snow.

The first serious round is shaping up for this weekend. The timing, length and intensity keep shifting. This is due to a cut-off low forming after the first storm line moves across Flagstaff. If the cut-off low forms mostly over Arizona, the rain will become snow and stick around longer. If it forms east of Arizona, then Flagstaff will get it’s scraps. The current GFS model run shows mostly rain falling on Saturday afternoon and evening, and then we get table scraps. A GFS run earlier today had a strong impact from Saturday evening through Tuesday morning with snow after Sunday morning. The Navy NAVGEM model predicts a stronger and longer storm.

The next, and probably stronger storm, is focusing on the following weekend. If the outlook continues as it is now, it will bring many forms of precipitation.

Details with both storms are likely to change.

US Navy NAVGEM model for precipitation rates, Saturday evening, February 12, 2017. (from Tropical Tidbits)

US Navy NAVGEM model for precipitation rates, Saturday evening, February 12, 2017. (from Tropical Tidbits)

 Posted by at 10:34 am

Wet end to February?

 Northern Arizona Weather, Outlooks, Winter Storms  Comments Off on Wet end to February?
Feb 052017
 
Experimental precipitation outlook for weeks 3-4 in the future. (Climate Prediction Center, 3 Feb. 2017)

With nearly 9 inches of precipitation between December and January, Things have been mostly dry since January 25. Next week, there is an occasional chance for flurries or light rain. It has been quite a change as the main storm track has been to the north. The current longer range outlooks for the second half of February are looking wetter.

Last Thursday, the Climate Prediction Center published their experimental 3 and 4 week outlook. It shows the potential for another round of wet weather.

Experimental precipitation outlook for weeks 3-4 in the future. (Climate Prediction Center, 3 Feb. 2017)

Experimental precipitation outlook for weeks 3-4 in the future. (Climate Prediction Center, 3 Feb. 2017)

This outlook is for February 18-March 3. Today, a run of the GFS model shows the potential for a significant storm around February 19. This is still a long way in the future. There are a few weaker storms in the computer model in the meantime. Stay tuned.

GFS model precipitation outlook for the morning of Sunday, February 19, 2017. (Image from Tropical Tidbits).

GFS model precipitation outlook for the morning of Sunday, February 19, 2017. (Image from Tropical Tidbits).

 

 Posted by at 10:47 am

Is snow season over?

 Northern Arizona Weather, Outlooks  Comments Off on Is snow season over?
Jan 252017
 
8-14 day precipitation outlook from the Climate Prediction Center.

With 43 inches of snow and 4.5 inches of water for the month to date, the next two weeks are looking remarkably dry. The question is how long will the dry trend last? The latest 8-14 day outlook from the Climate Prediction Center sums it up. Flagstaff ends up on the thin border between above and below normal precipitation. Will another snow storm hit after February 7?

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

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

 Posted by at 11:28 am

Friday was a record, will it show up in the record books? And, where will the next 12-18 inches of snow go.

 Northern Arizona Weather, Record, Winter Storms  Comments Off on Friday was a record, will it show up in the record books? And, where will the next 12-18 inches of snow go.
Jan 212017
 
GFS and NAM models total snowfall forecasts through Tuesday Morning. (From Tropical Tidbits)

UPDATED (9:52AM, January 22): Winter Storm Warning in effect. See below

Answers: I don’t know. And, on the ground, of course.

The National Weather Service provides two great products for looking at Flagstaffs weather. The Daily Climate Report and the Preliminary Monthly Climate Data Report. Yesterday, both reports were showing MM, or missing data for snowfall on both days. This has been repaired in the Monthly, but the Daily for January 20 still shows MM. The total snow fall was 12.6 inches. In the January 20 report, the record snowfall for the date was 7.1 inches in 1954. I wonder if it is still a record. Also, a Record Event Report archive is available. There is no report for January 20 or 21. I hope we don’t lose the data. This was a significant event.

Another interesting aspect, the snowfall amount broke the record, but the total precipitation amount did not. Must have been a warmer storm in 1954.

The bigger question is how deep will the next chunk of snow be? The GFS model caps it at a foot. The NAM model shows more, around 18 inches. You can see the difference in the image below. The Navy’s NoGaps model doesn’t run a snowfall calculation. But adding up the individual precipitation amounts and going with a rough 10 inches of snow for 1 inch of water, it looks like it is on the 18 inch side of the discussion. In any of these cases, it looks like the snow starts in earnest again on Sunday evening and goes through Tuesday. Current a Winter Winter Storm Watch is in effect. I would expect a that to change to a warning.

GFS and NAM models total snowfall forecasts through Tuesday Morning. (From Tropical Tidbits)

GFS and NAM models total snowfall forecasts through Tuesday Morning. (From Tropical Tidbits)

**********************

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE FLAGSTAFF AZ
945 AM MST SUN JAN 22 2017

...THE THIRD AND FINAL STORM IS EXPECTED TODAY INTO LATE MONDAY
NIGHT...

.THE NEXT STORM HAS ALREADY BEGUN TO AFFECT THE WESTERN HALF OF ARIZONA
THIS MORNING...AND WILL SPREAD EASTWARD LATER THIS EVENING THROUGH
MONDAY NIGHT. THERE IS A THREAT OF HEAVY SNOW ACCUMULATION FOR
AREAS ABOVE 6000 FEET ELEVATION...WITH LIGHTER ACCUMULATIONS DOWN
TO NEAR THE 5000 FOOT LEVEL.

AZZ004-006>008-015-230300-
/O.EXT.KFGZ.WS.W.0002.170122T1645Z-170124T1200Z/
KAIBAB PLATEAU-GRAND CANYON COUNTRY-COCONINO PLATEAU-
YAVAPAI COUNTY MOUNTAINS-WESTERN MOGOLLON RIM-
INCLUDING THE CITIES OF...JACOB LAKE...GRAND CANYON VILLAGE...
VALLE...FLAGSTAFF
945 AM MST SUN JAN 22 2017

...WINTER STORM WARNING NOW IN EFFECT UNTIL 5 AM MST TUESDAY
ABOVE 6000 FEET...

* TIMING...LIGHT TO MODERATE SNOW WILL CONTINUE THROUGH LATE THIS
  AFTERNOON...INCREASING IN INTENSITY AND CONTINUING THROUGH EARLY
  TUESDAY MORNING. SNOW WILL SPREAD FROM WEST TO EAST SUNDAY
  AFTERNOON AND EVENING...CONTINUING THROUGH TUESDAY MORNING.

* GENERAL EVENT TOTAL SNOW ACCUMULATIONS...8 TO 15 INCHES FOR
  AREAS ABOVE 6000 FEET ELEVATION. HIGHER AMOUNTS POSSIBLE ALONG
  SOUTHWEST FACING SLOPES OF THE MOGOLLON RIM AND THE KAIBAB
  PLATEAU. CONSULT POINT SPECIFIC FORECAST AT:
  WEATHER.GOV/FLAGSTAFF.

* SNOWFALL FORECAST FROM 9 AM MST TODAY UNTIL 5 AM MST TUESDAY...

     DONEY PARK  5 TO 9  INCHES       FLAGSTAFF  9 TO 15 INCHES
   GRAND CANYON  9 TO 15 INCHES      JACOB LAKE 11 TO 17 INCHES
      NORTH RIM 20 TO 26 INCHES           VALLE  4 TO 8  INCHES
       WILLIAMS  6 TO 10 INCHES

* WINDS...GUSTY WINDS ARE EXPECTED THROUGHOUT THE EVENT...WITH THE
  STRONGEST WINDS LATE TONIGHT THROUGH MONDAY AFTERNOON. SUSTAINED
  WINDS OVER 20 MPH WITH GUSTS UP TO 45 WILL SEVERELY REDUCE
  VISIBILITIES IN BLOWING AND DRIFTING SNOW.

* OTHER IMPACTS...DANGEROUS TRAVEL CONDITIONS ARE LIKELY DUE TO
  SNOW PACKED AND SLICK ROADS. VISIBILITY COULD ALSO BE SEVERELY
  REDUCED DUE TO BLOWING AND DRIFTING SNOW.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
EXPECTED OR OCCURRING...DUE TO SIGNIFICANT AMOUNTS OF SNOW AND
STRONG WINDS PRODUCING LIMITED VISIBILITIES.

DRIVING WILL BE EXTREMELY DANGEROUS DURING THIS STORM. FOR THE
LATEST ROAD CONDITIONS AND CLOSURES...CALL THE ADOT FREEWAY
MANAGEMENT SYSTEM AT 1 888 411 7623 OR VISIT THEIR WEB SITE AT
WWW.AZ511.COM.

ADDITIONAL WEATHER INFORMATION IS ON THE WEB AT
WWW.WEATHER.GOV/FLAGSTAFF.
 Posted by at 11:49 pm

Triple Header – Winter Storm Warning

 Northern Arizona Weather  Comments Off on Triple Header – Winter Storm Warning
Jan 182017
 
North American Mesoscale Model total snowfall for the first two storms. (From Tropical Tidbits)

Three waves of winter storms will move across the Northland between Thursday and Monday night. A Winter Storm Warning is in effect and included at the bottom of this post.

The first two waves my not be distinguishable from each other. Once the snow starts falling during the day on Thursday, it may not stop until during the night on Saturday. The break between the storms happens during the day on Friday. Heavier snow starts again in the late afternoon on Friday and continues into Saturday. Snow could be very heavy at times. As you can see in the North American Mesoscale model below, Flagstaff is easily in the 1-2 foot zone.

North American Mesoscale Model total snowfall for the first two storms. (From Tropical Tidbits)

North American Mesoscale Model total snowfall for the first two storms. (From Tropical Tidbits)

The National Weather Service has produced an interesting animation of snowfall amounts. Notice the heavier snowfall along the Mogollon Rim.

Snowfall amounts from Thursday to Saturday. (National Weather Service in Flagstaff)

Snowfall amounts from Thursday to Saturday. (National Weather Service in Flagstaff)

After a rest on Sunday, the snow will start again on Sunday evening and continue until Tuesday morning. This storm is not included in the current Winter Storm Warning. This storm could bring another 10-14 inches of snow. I expect another warning will be issued for this storm.

It’s difficult to differentiate between the shades of gray in the total snowfall image below. Flagstaff could be looking at 3 feet, or more, of snow over the next 5-6 days. Be careful. Enjoy The beauty with a mug of hot chocolate.

Total snowfall outlook from the GFS model. (from Tropical Tidbits)

Total snowfall outlook from the GFS model. (from Tropical Tidbits)

 

 

URGENT - WINTER WEATHER MESSAGE
 NATIONAL WEATHER SERVICE FLAGSTAFF AZ
 913 PM MST WED JAN 18 2017
 
 
 AZZ004-006-007-015-038-191900-
 /O.CON.KFGZ.WS.W.0001.170119T1300Z-170121T1900Z/
 KAIBAB PLATEAU-GRAND CANYON COUNTRY-COCONINO PLATEAU-
 WESTERN MOGOLLON RIM-OAK CREEK AND SYCAMORE CANYONS-
 INCLUDING THE CITIES OF...JACOB LAKE...GRAND CANYON VILLAGE...
 VALLE...FLAGSTAFF
 913 PM MST WED JAN 18 2017
 
 ...WINTER STORM WARNING REMAINS IN EFFECT FROM 6 AM THURSDAY TO
 NOON MST SATURDAY ABOVE 5500 FEET...
 
 * TIMING...LIGHT TO MODERATE SNOW WILL DEVELOP AND SPREAD FROM 
   WEST TO EAST DURING THE DAY THURSDAY. MODERATE TO HEAVY SNOW 
   WILL DEVELOP THURSDAY NIGHT...DECREASING IN INTENSITY DURING 
   THE DAY FRIDAY. A SECOND WAVE OF MODERATE TO HEAVY SNOW WILL 
   DEVELOP FRIDAY EVENING THROUGH SATURDAY MORNING. 
 
 * GENERAL EVENT TOTAL SNOW ACCUMULATIONS...DEPENDING ON YOUR 
   LOCATION WITHIN THE WARNING AREA...EXPECT 8 TO 16 INCHES 
   BETWEEN 5500 AND 7000 FEET AND 12 TO 24 INCHES ABOVE 7000 
   FEET. CONSULT POINT SPECIFIC FORECASTS AT: 
   WEATHER.GOV/FLAGSTAFF. 
 
 * SNOWFALL FORECAST FROM 6 AM MST THURSDAY UNTIL NOON MST 
   SATURDAY...
 
      DONEY PARK 10 TO 16 INCHES       FLAGSTAFF 16 TO 22 INCHES
    GRAND CANYON 12 TO 18 INCHES      JACOB LAKE 14 TO 20 INCHES
       NORTH RIM 20 TO 26 INCHES           VALLE  9 TO 15 INCHES
        WILLIAMS 18 TO 24 INCHES
 
 PRECAUTIONARY/PREPAREDNESS ACTIONS...
 
 A WINTER STORM WARNING MEANS SEVERE WINTER WEATHER CONDITIONS ARE
 EXPECTED OR OCCURRING...DUE TO SIGNIFICANT AMOUNTS OF SNOW AND
 STRONG WINDS PRODUCING LIMITED VISIBILITIES.
 
 DRIVING WILL BE EXTREMELY DANGEROUS DURING THIS STORM. FOR THE
 LATEST ROAD CONDITIONS AND CLOSURES...CALL THE ADOT FREEWAY
 MANAGEMENT SYSTEM AT 1 888 411 7623 OR VISIT THEIR WEB SITE AT
 WWW.AZ511.COM.
 
 ADDITIONAL WEATHER INFORMATION IS ON THE WEB AT
 WWW.WEATHER.GOV/FLAGSTAFF.

 

 Posted by at 9:47 pm
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