November: Feast or Famine
December 02, 2003
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November: Feast or Famine
By Derek Arndt
Assistant State Climatologist
Oklahoma Climatological Survey
12/2/03
Another November has ended and will go on the record as dry. November 2003 precipitation totals are about an inch below the statewide normal of 2.83 inches. That puts it pretty close to the middle of the historical population.
How can this be? Well, two factors are at play here. First, the 30-year normal precipitation totals for November are near their highest levels ever, due to very wet Novembers during the 1980s and 1990s. Second, November is a very bipolar month in the climate record, much like its autumn brethren September and October. In other words, November is either significantly wet, or significantly dry, but hardly ever in between.
The likelihood of total precipitation landing within a quarter-inch of the long-term average for the month is quite low: it happens about once every nine or ten years in most of Oklahoma's climate divisions.
In fact, falling within an inch (plus or minus) of the long-term average is a 50-50 proposition for most of Oklahoma. Out of the 109 Novembers on record since 1895, the table below shows the number of times the precipitation has been within a quarter-inch, half-inch or inch of the long-term average:
| Climate Division | Long-Term Average | Within Qtr-inch | Within Half-inch | Within an inch | | | | | | | Panhandle
| 0.88" | 27 of 109 | 44 of 109 | 93 of 109 | | N. Central | 1.64" | 13 of 109 | 30 of 109 | 49 of 109 | | Northeast | 1.43" | 15 of 109 | 23 of 109 | 44 of 109 | | W. Central | 1.43" | 14 of 109 | 28 of 109 | 64 of 109 | | Central | 2.15" | 11 of 109 | 29 of 109 | 47 of 109 | | E. Central | 3.18" | 13 of 109 | 26 of 109 | 41 of 109 | | Southwest | 1.48" | 11 of 109 | 26 of 109 | 58 of 109 | | S. Central | 2.46" | 15 of 109 | 28 of 109 | 41 of 109 | | Southeast | 3.98" | 14 of 109 | 17 of 109 | 31 of 109 |
Obviously, the occurrences are relatively larger in the western divisions because the long-term average is so low (for example, a month with zero precipitation is within an inch of the panhandle's 0.88" average).
So, let's look at the same issue, but break it down by percentages. Here's a table showing how often the November precipitation is within 10%, 25% or 50% of the long-term average.
| Climate Division | Long-Term Average | Within 10% | Within 25% | Within 50% | | | | | | | Panhandle
| 0.88" | 8 of 109 | 22 of 109 | 41 of 109 | | N. Central | 1.64" | 11 of 109 | 20 of 109 | 40 of 109 | | Northeast | 1.43" | 17 of 109 | 30 of 109 | 55 of 109 | | W. Central | 1.43" | 9 of 109 | 22 of 109 | 46 of 109 | | Central | 2.15" | 8 of 109 | 32 of 109 | 48 of 109 | | E. Central | 3.18" | 15 of 109 | 32 of 109 | 60 of 109 | | Southwest | 1.48" | 6 of 109 | 20 of 109 | 41 of 109 | | S. Central | 2.46" | 15 of 109 | 31 of 109 | 52 of 109 | | Southeast | 3.98" | 17 of 109 | 30 of 109 | 53 of 109 |
Just for clarity, the criterion for that last column is this: if a November is between the long-term average and plus or minus HALF of that long-term average, it counts. In parts of Oklahoma, almost two-thirds of Novembers are outside this range!
So, a significantly dry (or wet) November is certainly not uncommon. What is significant about this November is that it follows several very dry months in a row. The cumulative effect of these low-precipitation months is causing significant-to-severe problems for much of the western half of the state.
Media Contact:
Cerry Leffler
Oklahoma Climatological Survey
100 E. Boyd, Suite 1210
Norman, OK 73019-1012
405-325-2541
405-325-2550 (fax)
cerry@ou.edu
For Additional Information:
Derek Arndt
Climatologist
100 E. Boyd, Suite 1210
Norman, OK 73019-1012
405-325-2541
405-325-2550 (fax)
darndt@ou.edu
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