Ticker for December 1, 2003

                
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December 1, 2003   December 1, 2003   December 1, 2003   December 1, 2003


November: Feast or Famine

Another November is in the books, and it was a dry November.  The
month will go on record as about an inch below the statewide normal
of 2.83 inches of precipitation. 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
normals for November are near their highest levels ever, thanks to
the very wet Novembers of 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.

In fact, the likelihood of 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, landing within an inch (plus or minus!) of the long-term
average is a 50-50 proposition for most of Oklahoma.  In fact, out
of the 109 Novembers on record since 1895, here are the number of
times the precipitation landed within a quarter-inch, half-inch or
inch of the long-term average:

Climate    Long-term    Within      Within      Within
Division   Average      Qtr-inch    Half-inch   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 precip 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 precip lands within
10%, 25% or 50% of the long-term average.

Climate    Long-term    Within      Within      Within
Division   Average      10 percent  25 percent  50 percent

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 criteria for that last column is this: if a
November lands between the long-term average 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-precip
months is causing significant-to-severe problems for much of the
western half of the state.