Rain's Early Fall Smashes Pacific Northwest Precipitation Records

September 30 Update: September monthly precipitation records have also been set in Oregon at Eugene, Hillsboro, McMinnville (second highest), Portland (downtown and airport), and Salem, as well as at Vancouver, Washington. Details have been added below.

Original post:
Driven by persistent abnormally low pressure in the northeastern Pacific, an early onset of the rainy season is smashing precipitation records for September in the Pacific Northwest. Through this morning, Astoria, Oregon had broken century-plus records for all-time wettest September (by over 1"), wettest September day (by almost 1"), and wettest 2-day and 3-day totals for September. These records were further extended by the 2.00" which had fallen through 4 pm this afternoon, tying the daily record for Sept. 29 from 1951 and bringing the monthly total to date to 10.10", which is just 0.10" less than 500% of normal.

The rainfall map above shows that large parts of coastal Oregon have seen precipitation for the month of September to date (through the 28th) which is over 400% of average, with some areas over 600%.

The map to the right (click to enlarge) shows the pressure pattern Saturday evening over North America near the middle of the atmosphere, expressed as the standard deviation of the height of the 500 mb level. There is a huge area of greater than 3 standard deviations below average along the coast and offshore of the Pacific Northwest and British Columbia. (Note that in a randomly distributed "bell curve", 99.7% of all observations would be within 3 standard deviations of the average.)


The National Weather Service (NWS) report for Astoria:

AS OF 11 AM THIS MORNING...OVER 5 INCHES OF RAIN HAVE FALLEN ON 
 ASTORIA AIRPORT THIS WEEKEND. THIS RAINFALL HAS SHATTERED NUMEROUS 
 SEPTEMBER RECORDS...REMARKABLE CONSIDERING THAT RECORDS HAVE BEEN 
 KEPT IN ASTORIA SINCE 1890.
 
    RAINFALL RECORDS BROKEN IN ASTORIA
 ----------------------------------------
 
 1. ALL-TIME WETTEST SEPTEMBER ON RECORD...
    1. SEP 2013......... 9.70 INCHES AND COUNTING.
    2. SEP 1906......... 8.66 INCHES.
    3. SEP 1920......... 8.55 INCHES.
    4. SEP 1905......... 7.38 INCHES.
 
 2. WETTEST SEPTEMBER DAY ON RECORD...
    1. SEP 28 2013...... 3.56 INCHES.
    2. SEP 16 1997...... 2.67 INCHES.
    3. SEP 30 1953...... 2.41 INCHES.
    4. SEP 13 1935...... 2.27 INCHES.
 
 3. WETTEST 2-DAY TOTAL FOR SEPTEMBER...TOP 2 NOW SET IN 2013.
    1. SEP 28-29 2013... 5.16 INCHES AND COUNTING.
    2. SEP 27-28 2013... 4.55 INCHES.
    3. SEP 3-4 1913..... 3.46 INCHES.
    4. SEP 16-17 1997... 3.42 INCHES.
 
 4. WETTEST 3-DAY TOTAL FOR SEPTEMBER...
    1. SEP 27-29 2013... 6.15 INCHES AND COUNTING.
    2. SEP 2-4 1913..... 4.31 INCHES. 
    3. SEP 15-17 1997... 4.16 INCHES. 

In Washington state, daily rainfall records were set for September 28 at Seattle-Tacoma, Olympia, Hoquiam, and Quillayute. An inspection of National Climatic Data Center records indicates that the 2.93" at Olympia was not only more than triple the old record, it was also an all-time daily record for September, well above the 1.67 on Sept. 17, 2010. Olympia records began in 1948. The NWS reports:

A RECORD RAINFALL OF 2.93 INCHES WAS SET AT OLYMPIA WA AIRPORT ON
SEP 28TH. THIS BREAKS THE OLD RECORD OF 0.82 SET IN 1971.

A RECORD RAINFALL OF 1.71 INCHES WAS SET AT SEATTLE-TACOMA WA
AIRPORT ON SEP 28TH. THIS BREAKS THE OLD RECORD OF 0.83 SET IN 1948.

A RECORD RAINFALL OF 1.78 INCHES WAS SET AT HOQUIAM WA AIRPORT ON
SEP 28TH. THIS BREAKS THE OLD RECORD OF 1.02 SET IN 1962.

A RECORD RAINFALL OF 1.93 INCHES WAS SET AT QUILLAYUTE WA AIRPORT
ON SEP 28TH. THIS BREAKS THE OLD RECORD OF 1.32 SET IN 1971.

The NWS reported on September 30 that several other locations in Washington and Oregon have set September rainfall records:

1. ASTORIA (1890)...
   1. SEP 2013......... 10.51 INCHES AND COUNTING.
   2. SEP 1906......... 8.66 INCHES.
   3. SEP 1920......... 8.55 INCHES.
   4. SEP 1905......... 7.38 INCHES.
      CLIMATOLOGICAL NORMAL: 2.14 INCHES.

2. EUGENE (1890)...
   1. SEP 2013......... 6.16 INCHES AND COUNTING.
   2. SEP 1927......... 5.21 INCHES.
   3. SEP 1911......... 4.91 INCHES.
   4. SEP 1986......... 4.65 INCHES.
      CLIMATOLOGICAL NORMAL: 1.29 INCHES.

3. HILLSBORO (1929)...
   1. SEP 2013......... 6.10 INCHES AND COUNTING.
   2. SEP 1945......... 3.68 INCHES.
   3. SEP 1982......... 3.46 INCHES.
   4. SEP 1977......... 3.43 INCHES.
      CLIMATOLOGICAL NORMAL: 1.26 INCHES.

4. MCMINNVILLE (1894)...
   1. SEP 1996......... 7.58 INCHES.
   2. SEP 2013......... 5.58 INCHES AND COUNTING
   3. SEP 1901......... 4.83 INCHES.
   4. SEP 1914......... 4.28 INCHES.
      CLIMATOLOGICAL NORMAL: 1.31 INCHES.

5. PORTLAND AIRPORT (1940)...
   1. SEP 2013......... 5.06 INCHES AND COUNTING.
   2. SEP 1986......... 4.30 INCHES.
   3. SEP 1982......... 3.98 INCHES.
   4. SEP 1945......... 3.96 INCHES.
      CLIMATOLOGICAL NORMAL: 1.47 INCHES

6. PORTLAND DOWNTOWN (1872)...
   1. SEP 2013......... 6.21 INCHES AND COUNTING.
   2. SEP 1927......... 5.52 INCHES.
   3. SEP 1911......... 5.19 INCHES.
   4. SEP 1969......... 4.87 INCHES.
      CLIMATOLOGICAL NORMAL: 1.54 INCHES.

7. SALEM (1872)...
   1. SEP 2013......... 6.63 INCHES AND COUNTING.
   2. SEP 1927......... 5.52 INCHES.
   3. SEP 1911......... 5.19 INCHES.
   4. SEP 1969......... 4.87 INCHES.
      CLIMATOLOGICAL NORMAL: 1.28 INCHES.

7. VANCOUVER, WA (1896)...
   1. SEP 2013......... 4.98 INCHES AND COUNTING.
   2. SEP 1911......... 4.88 INCHES.
   3. SEP 1925......... 4.46 INCHES.
   4. SEP 1927......... 4.35 INCHES.
      CLIMATOLOGICAL NORMAL: 1.56 INCHES.