Forecast Accuracy

I’ve been tracking accuracy of my forecasts for a few years but have never actually posted it online.  After getting tired of the “you guys are ALWAYS wrong” calls and emails, I figured it’s time to post the stats online:

The criteria:  I track low/high forecast temp for PDX (Portland International Airport), a central location in the metro area.  I track just my forecasts which are generally Monday-Friday.  The forecast must be within 3 degrees of the actual temp for the following calendar day.  For rainfall it’s a bit more straightforward;  if rain is forecast and it is too little to get measured at PDX I’m wrong.  Same with a no rain forecast and rain actually arrives.  In the comments section I give my thoughts and grade myself down if the numbers down seem to represent reality.  For example:  I say it’s going to rain tomorrow by late morning.  Then let’s say the rain doesn’t arrive until 11pm, leaving the day “rainy” in the climate stats, but to any normal person it didn’t REALLY rain.  Got to mark myself down some for that.  Or there is no category for “major screwups” (2-7″ unexpected snowfall 12/2009), which don’t really fall into rain/clouds or temp columns.

Chief Meteorologist Mark Nelsen

Dates  DAYS TRACKED TEMP % CORRECT RAIN % CORRECT TOTAL % CORRECT COMMENTS
2014
Dec 31-Jan 4 4 50% 100% 75% Terrible job with temps
Jan 7-11 5 60% 100% 80% Missed several high temps…too warm!
Jan 14-18 5 50% 100% 75% Missed half the highs and lows.  Inversion messing w/forecasts
Jan 21-25 5 80% 100% 90% Forecast 2 low temps too warm, otherwise good
Jan 28-Feb 1 5 80% 80% 80% Missed two highs and one rain/clouds day
Feb 4-0 7 100% 71% 86% Challenging snowy week.  Temps perfect, but too heavy on snow forecast
Feb 11-16 6 75% 100% 82% Missed two low temps
Feb 18-21 4 100% 100% 100% Good week!
Feb 28-Mar 1 2 75% 100% 82% Missed one low temp
Mar 4-8 5 80% 100% 90% Good week, but missed high/low one day
Mar 11-15 5 100% 100% 100% Good week, no missed highs/lows
Mar 18-22 5 80% 100% 90% Good week, but missed two low temperatures
Mar 24-28 Vacation – Spring Break
Apr 2-5 4 87% 100% 94% Good week, just missed one high temp.  Rain forecasts okay
Apr 8-11 4 80% 80% 80% Missed one low temp.  Rained one day when dry forecast
Apr 15-19 5 90% 100% 95% Missed one low temperature. Good rain forecasts
Apr 22-25 4 100% 100% 100% Great week!

 

Dates

 

DAYS TRACKED

TEMP % CORRECT

RAIN % CORRECT

TOTAL % CORRECT

COMMENTS

2013

Jan 1-5

4 days

75%

100%

87%

Missed 1 low and 1 high.  Rain/clouds okay.

Jan 8-12

5 days

80%

100%

90%

Missed 1 low and 1 high.  Good snow dusting forecast.

Jan 15-19

5 days

50%

80%

65%

Flunked.  Chased low/high temps all week due to inversion…grrr!

Jan 21-25

5 days

70%

80%

75%

Freezing Rain forecast = Wrong!

Jan 29 – Feb 2

5 days

100%

100%

100%

Good week!  But boring weather.

Feb 5-8

4 days

80%

100%

90%

Missed one low temp

Feb 12-16

5 days

80%

100%

90%

Missed one low and one high

Feb 18-22

5 days

90%

100%

95%

Missed on high temp, rainy week = good forecast

Feb 25-1

-

-

-

-

Vacation

Mar 5-9

-

-

-

-

Vacation

Mar 12-16

5 days

90%

80%

85%

Good week, missed one low and one rain (none) day

Mar 19-23

5 days

90%

100%

95%

Good week, missed one low, wx/rain was correct

Apr 2-6

5 days

70%

100%

82%

Missed 3 temps, fine on clouds and rain

Apr 9-13

5 days

70%

100%

83%

Missed 3 temps, good fcst clouds/rain

Apr 16-20

5 days

90%

80%

85%

Decent week, one day too nice, so high temp was wrong

Apr 23-27

5 days

90%

95%

93%

Sunny week, missed one low temp, rain slightly early Sat.

Apr 30-May 3

4 days

100%

100%

100%

Good week!

May 7-11

5 days

70%

80%

75%

Missed 3 highs/lows and marine layer didn’t clear one day

May 14-18

5 days

90%

100%

95%

Missed one high temp…good week

May 21-25

4 days

63%

100%

81%

Missed two lows and one high.  Rain/clouds forecast was fine though.

May 28-June 1

5 days

100%

100%

100%

Perfect week!

June 4-8

5 days

100%

100%

100%

Another perfect week!

June 10-14

-

-

-

-

Vacation

June 18-22

5 days

90%

100%

95%

Missed one high temp, a good week

June 24-28

Weather Conference

July 2-6

4 days

80%

90%

85%

Missed one high temp and low clouds stuck around too long

July 8-13

5 days

80%

100%

90%

Good week, too cool on last day

July 14-28

Vacation

Jul 29-Aug3

4 days

75%

50%

68%

Bad week, missed marine layer twice!

Aug 4-11

Vacation

Aug 13-17

5 days

90%

100%

80%

Good week, missed one high temp

Aug 19-26

Vacation

Aug 27-30

4 days

63%

100%

81%

Rough week, missed 3/8 of temps!

Sept 3-7

5 days

80%

80%

80%

Missed two temps, nailed heavy rain forecast though

Sept 10-13

4 days

75%

50%

63%

Missed marine layer 2 days in a row…brutal temp & cloud forecast

Sept 17-21

5 days

100%

90%

95%

Good week, Saturday was wetter than expected, thunder too!

Sept 24-28

5 days

90%

100%

95%

Good week, missed one high temp

Oct 1-5

5 days

80%

100%

90%

Missed two high temps

Oct 8-12

5 days

90%

100%

95%

Good week, missed a low temp

Oct 15-16

2 days

100%

100%

100%

Just a two day week

Oct 24-26

3 days

67%

100%

83%

Missed 1/3 of low temps, too many warmer than expected nights

Oct 29-Nov 2

5 days

80%

100%

90%

Missed two high temps

Nov 12-16

5 days

80%

100%

90%

Missed two low temps, wx forecast was good

Nov 19-23

5 days

80%

100%

90%

Missed two low temps

Dec 3-7

5 days

90%

80%

85%

Missed low temp and 1-3” snow Clark county and Scappoose.

Dec 10-14

5 days

80%

100%

90%

Missed one low and one high

Dec 17-21

5 days

70%

100%

82%

Missed 3 of 10 lows/highs

Dec 26-30

5 days

60%

80%

70%

Major inversion fcst issues, missed numerous lows/highs

2012

Dates

 

DAYS TRACKED

TEMP % CORRECT

RAIN % CORRECT

TOTAL % CORRECT

COMMENTS

2012

Jan 3-7

5 days

70%

100%

82%

Missed 3 of 10 lows/highs, rain okay

Jan 10-16

7 days

  86%

100%

93%

Good week, hit weekend snow forecast well (not much in showers).

Jan 17-21

5 days

80%

90%

85%

Missed two highs, snow forecast okay, but not perfect.

Jan 24-28

5 days

60%

100%

80%

Missed 4 highs and lows…warm south wind & cold east wind battle messed me up.

Jan 31 – Feb 4

5 days

90%

100%

95%

Only missed 1 high!  A good week

Feb 8-10

3 days

67%

100%

83%

Bad week for temps, much warmer than expected.  Clouds & rain were good.

Feb 14-18

5 days

90%

100%

95%

Missed one low, otherwise great.  Fine on clouds & rain.

Feb 22-26

5 days

70%

100%

85%

Missed two lows and one high.  Challenging snow forecast turned out great though!

Feb 28 –Mar 5

5 days

80%

100%

90%

Missed two low temps, rain/snow forecasts went well!

Mar 6-10

5 days

90%

100%

95%

Good forecasts, missed first 66 day of spring, no complaints

Mar 13-16

4 days

80%

100%

90%

Missed 1 high temp, good rain/snow forecasts

Mar 19-30

Vacation

Apr 4-8

5 days

70%

100%

85%

Missed 3 highs/low, rain/clouds forecast okay.

Apr 10-14

5 days

90%

80%

85%

Missed one high and one day it rained all day instead of P.M. only.

Apr 17-21

5 days

80%

80%

80%

Missed two high temps, one day cloudier and cooler than expected

Apr 24-28

5 days

90%

80%

85%

Missed one low and one rain day

May 1-5

5 days

100%

90%

95%

Nailed all temps, but one day’s clouds and sprinkles weren’t expected

May 7-12

5 days

100%

100%

100%

Perfect!

May 14-18

Vacation

May 22-26

5 days

80%

80%

80%

Missed two high temps and big thunderstorm Saturday evening

May 29-Jun 2

5 days

90%

100%

95%

Missed one low..dry Starlight Parade!

Jun 5-9

5 days

80%

100%

90%

Missed 2 high temps, rain & sun forecast was good

Jun 11-19

Vacation

Jun 21-23

3 days

100%

100%

100%

Good short week, one nice sunny day

Jun 26-30

5 days

100%

80%

90%

Missed one rain day, otherwise good

Jul 2-6

4 days

100%

100%

100%

Great 4th of July Week!

Jul 9-13

Vacation

Jul 17-20

4 days

80%

100%

90%

Missed one high temp (too many clouds)

Jul 23 – Aug 3

Vacation

Aug 4-10

7 days

93%

86%

90%

Missed one day (clouds all day) and one high temp

Aug 13-17

Vacation

Aug 20-24

Wx Conf

Aug 27-31

5 days

90%

100%

95%

Easy forecast, sunny most days, missed one low temp

Sept 5-8

3 days

83%

67%

75%

Missed a high temp and surprise t’storms in Portland late afternoon.

Sept 12-16

5 days

90%

100%

95%

Missed on high temp (too cool)

Sept 25-28

4 days

75%

75%

75%

Missed one high and one low, plus too cloudy/wet of a forecast one day

Oct 2-5

4 days

75%

100%

87%

Missed two low temps, annoying east wind dropped off = cold.

Oct 9-12

4 days

75%

100%

87%

Missed two high temps, bad week

Oct 16-20

5 days

90%

100%

95%

Missed on high temp, good week otherwise

Oct 23-27

5 days

80%

100%

90%

Missed one high and low…warm south wind arrived too early

Oct 30-2

4 days

100%

100%

100%

100%!!!  Temps all within 3 degrees, off/on rain all week well forecast

Nov 6-9

4 days

63%

80%

71%

Yikes!  A brutal week, missed almost half the temps

Nov 12-15

4 days

100%

80%

90%

Temps perfect, but fog didn’t clear off in a reasonable fashion one day.

Nov 20-26

5 days

80%

100%

90%

One high and one low missed, rain okay

Nov 28-Dec2

5 days

90%

100%

95%

Missed on high temp, otherwise a good week.

Dec 4-7

4 days

62.5%

100%

81%

Bad week, missed 3 low/high temps, rain/clouds okay.

Dec 11-15

5 days

70%

80%

75%

Major miss, forecast big windstorm; it didn’t show up

Dec 18-22

Vacation

Dec 26-30

5 days

80%

100%

90%

Missed one high/low, very dry week.

 2009-2011

2011

FCST DAYS

TEMPS

CORRECT

RAIN &

CLOUDS

CORRECT

FINAL GRADE

COMMENTS

Jan 3-9

5 days

60%

100%

80%

Missed 2 lows, 2 highs…I hate east wind.

Jan 10-14

5 days

80%

80%

80%

Dry one day w/rain fcst.  Missed one high & one low

Jan 17-20

4 days

88%

100%

94%

Missed one high temp

Jan 24-27

4 days

88%

80%

84%

Missed one high temp and forecast rain when only a sprinkle or two fell.

Jan 31-Feb 7

5 days

90%

100%

95%

Only missed one low temp by 4 deg.

Feb 8-11

4 days

80%

100%

90%

Missed one low temp…good week

Feb 15-19

5 days

70%

80%

75%

Rough week, missed 3 highs/lows and one wet day when expected dry.

Feb 22-26

5 days

100%

100%

100%

Snow & cold week…100% highs and hit snow amounts well!

March 1-3, 6-7

5 days

70%

100%

85%

Missed two lows and one high…dog chasing it’s tail while forecasting?

March 8-11

4 days

62%

100%

81%

Missed almost ½ of highs & lows…rain forecast perfect though.

March 15-19

5 days

80%

100%

90%

Missed one low and one high…rained every day!

March 22-26

Vacation

Mar 29-Apr 2

Vacation

April 5-9

5 days

80%

80%

80%

Missed two lows, and one dry day not expected.

April 12-16

5 days

80%

80%

80%

Clouds/Showers Saturday, bad forecast.  Missed high & low too!

April 20-23

4 days

75%

100%

87%

Missed two low temperatures

April 26-30

5 days

90%

80%

85%

One day w/no rain when forecast.  Too cool for one high temp.

May 10-14

5 days

70%

100%

85%

Missed one high and 2 lows

May 17-20

4 days

100%

100%

100%

Excellent week, everything worked out right!

May 25-29

5 days

80%

90%

85%

Missed one low, one high, and slightly missed a showery day (drier than expected)

May 31-Jun 4

5 days

100%

100%

100%

A great week!  No missed temps, plus accurate forecast of first real warm weather (timing & temps)

June 5-10

5 days

80%

100%

90%

Missed two high temps, forecast too warm.

June 14-17

4 days

75%

100%

87%

Missed a low by…well…7 degrees!  Otherwise a good week.

June 20-24

At Weather Conference

Jun 28-Jul2

4 days

83%

100%

92%

Only missed one high by one degree, good otherwise

July 6-8

3 days

67%

100%

84%

Ouch…missed a high and low

July 9-17

Vacation

July 19, 21, 22

3 days

67%

100%

84%

Missed a low and just barely a high.  Showers in mid July!

July 22-Aug 7

Vacation

Aug 8-12

5 days

70%

80%

75%

Challenging marine layer!  Missed 3 lows/highs, plus cloudy day.

Aug 16-19

4 days

100%

100%

100%

Perfect week!

Aug 23-27

Vacation

Aug 30-Sep 3

5 days

100%

100%

100%

Perfect week!

Sept 6-10

5 days

80%

100%

90%

Missed one high and one low.  Clouds/rain forecast was “spot on”

Sept 13-17

5 days

30%

60%

45%

Worst Ever!  Missed numerous highs/lows due to marine clouds, then unexpected rain.

Sept 20-25

6 days

83%

100%

92%

Much better.  Just missed two low temps by more than 3 degrees.

Sept 27-Oct 1

5 days

80%

80%

80%

Missed one high and one low (out of 10), rained one day (not fcst)

Missing

Oct 18-23

6 days

58%

83%

71%

Bad week, missed 5 of 6 lows (warm nights).  Clouds/precip fcst okay.

Oct 25-28

4 days

100%

100%

100%

Yes!  Finally a good week; good forecasting.

Nov 1-5

5 days

60%

80%

70%

Missed 4 of 10 temps…ugh!  One cloud/rain day was missed.

Nov 8-12

6 days

83%

100%

92%

A good week, extra work day

Nov 15-19

5 days

70%

100%

87%

Inversion screwed up high temps on 2 days, one low temp missed

Nov 22-23, 26

3 days

83%

100%

92%

Missed one low temperature

Nov-Dec 29-4

5 days

80%

90%

85%

Missed two high temps (too much fog), and one day fog barely burned off.

Dec 6-7, 12

3 days

67%

100%

83%

Missed one high and low temp, clouds/rain okay.

Dec 27-Jan2

6 days

91%

100%

95%

Missed one high temp

Dates

 

DAYS TRACKED

TEMP % CORRECT

RAIN % CORRECT

TOTAL % CORRECT

COMMENTS

2010

Jan 5-9

5 days

100%

100%

100%

A bit better!

Jan 11-15

5 days

90%

100%

95%

Jan 18-22

5 days

90%

90%

90%

Missed a high one day and marginal rain forecasting = -10%

Jan 25-27

3 days

50%

67%

58%

Flunked!  Missed rainy day and 2 bad temp forecasts

Feb 2-6

5 days

100%

90%

95%

Saturday: Cloudier and drippy (-10%)

Feb 9-13

5 days

40%

100%

70%

A massacre: All 5 days high temps off by 4 degrees+!

Feb 16-20

5 days

70%

100%

85%

Two sunny days my highs were too low.  No one minds those mistakes right?

Feb 23-27

5 days

90%

100%

95%

A good week!

March 5-13

5 days

70%

100%

75%

3 out of 10 temps missed…bad

March 16-Apr 1

Vacation

-

-

-

-

Apr 6-10

5 days

80%

90%

85%

A decent week

Apr 13-17

5 days

90%

80%

85%

1 morning colder than expected: Saturday T’Storm = Bad!

Apr 20-26

5 days

90%

100%

95%

Pretty good week, missed one low

April 29-May 2

4 days

100%

80%

90%

Surprise rain one day earlier than expected

May 4-8

5 days

80%

80%

80%

Surprise PM Showers in spots on “Mostly Sunny” day!

May 11-15

5 days

90%

100%

95%

Missed one low temp

May 25-29

5 days

60%

100%

80%

Brutal misses on temp forecasts, rained every day, so okay with that.

June 8-12

5 days

80%

90%

85%

Showers one day when not in forecast…bad.

June 16-20

5 days

80%

80%

80%

Missed 2 highs and rained one day when supposed to be dry.

June 29-July 3

5 days

100%

60%

80%

2 days with downpours when only a sprinkle expected.  Vancouver soaked 1”+

July 6-9

4 days

80%

100%

90%

Easy week, sunny & hot, nailed heatwave

July 13-17

5 days

90%

100%

95%

Good week, sunny & dry, missed one low temp

Aug 24-28

5 days

70%

90%

80%

Rough temp forecasts…missed 3 of 10!  One day w/showers not expected on weekend.

Aug 31-Sept 4

5 days

90%

100%

95%

Good forecasting, hot weather okay, hit first good rain in 2 months correctly!

Sept 7-11

5 days

90%

90%

90%

Technically correct on rain/weather, but took off 10% because Fridaylow clouds took ALL day to turn to “PM Sunshine”.

Sept 14-18

5 days

60%

100%

80%

Challenging week with temperatures.  Cloud cover screwed up 4 high & low temps…grrr!

Sept 19, 21-24

5 days

100%

100%

100%

A very good week.  Things finally worked out perfectly for once.

Oct 4-9

5 days

80%

100%

90%

Not too bad, missed two lows

Oct 19-23

5 days

80%

100%

90%

Good forecasts in general, but 2 nights warmer than expected

Oct 26-30

5 days

90%

100%

95%

Missed one low temp, but good otherwise.

Nov 1-5

5 days

100%

100%

100%

Wow!  Everything worked out perfectly for once.

Nov 9-13

5 days

90%

100%

95%

Missed one low temp (colder than expected).  Rainfall was good.

Nov 15-20

6 days

100%

100%

100%

Great Week!

Nov 22-26

Only forecast 2 days

Nov 29-Dec 3

4 days

67%

100%

83%

Missed 3 of 8 temps, good rain fcsts though.

Dec 7-9

3 days

100%

100%

100%

Great Week!

Dec 13-16

4 days

87%

100%

93%

Missed one high, a 55 deg. Day…warm

Dec 20-24

Vacation Week

Dec 27-30

4 days

70%

100%

85%

Missed 2 highs and 1 low

2009

Nov 24-30

5 days

70%

100%

85%

Dec 1-5

5 days

60%

100%

80%

Lots of bad lows, dry week

Dec 8-12

5 days

80%

80%

80%

Missed 1 hi & 1 lo.

Dec 14-27

None

Lots of vacation

Dec 29-Jan 2

4 days

63%

100%

82%

Snow disaster =  subtract 50%!

11 Responses to Forecast Accuracy

  1. Evelyn Fuller says:

    Hey y’all, on ur weather broadcast last week and today u have wrong info Damascus is in Gresham’s place on the map. Pleadease fix it. Thank you!

  2. sajtsajt says:

    Your percentages are great, because weather predictions more then 2 days are with low accuracy.

  3. William T. Matthews says:

    There was a snow storm on March 15 2002 with hugh snow flakes
    in Columbia county, we know this as a fact because this was our first date almost 10 years ago. There was a motor vehicle accident that night 2 miles south of Rainier, Oregon due to snow.

  4. gidrons says:

    Do you track accuracy 3 days out?

  5. I am totally delighted with your weather predictions!!! .This gal has been tracking seismic activity and a quake is forecasted for the 10th by the geological service and she agrees and shows why. I thought it deserved a look!!! Please look at the video? Tx, Della

  6. bobby says:

    how long is it going to rain today???

  7. bobby says:

    great call on the no rain we are receiving right now missed that one genius!

  8. Timmy_Supercell (Hillsboro) says:

    Nice one! I agree with the percentages so far…

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