Each
Sunshine
Guide represents my professional judgment as to what the
most likely weather conditions will be at that destination for the foreseeable
future. They are professional opinions
and forecasts. They are not simple
compilations of past weather.
Have
I studied the past weather and its statistical compilations? Of course I have.
But
I have done more than simply regurgitated the statistics. I have evaluated each set of data in terms of
when it was done, what period of years it covered, where within the destination
area it was recorded (airport, city center, university, military base, etc.), how
reliable I feel it to be, and how representative it is of those particular
parts of the destination area that most travelers are likely to visit.
I
have also taken into account trends in climatic characteristics; that is, how
the present is different from the past and how the future is likely to be
different from the present.
Many
people mistakenly believe that each city has one particular “official” weather
station, and that that station has published one set of data that properly and
officially characterize that location.
Nothing could be farther from the truth.
Climatic characteristics vary widely over the metropolitan area of a
particular city. Temperatures alone can
vary by ten or fifteen degrees from the city center to the suburbs, or from
that center to the airport. Rainfall
varies, as do most of the other characteristics that you will find in my Guides.
Although
the bulk of meteorological data are now collected at airports, and that is
where forecasters are stationed, most cities have an additional network of cooperative
observers scattered over the metropolitan area.
These may be universities, military installations, small local airports,
or just private citizens who maintain collection sites with standardized
instruments. In the
These
collection points come and go over the years, as do the first-order
meteorological sites. Meteorological
data for cities used to be collected in those cities, usually in some sort of
federal office building (quite often, the roof of the post office). Nowadays, the data is collected out at the
airport, even though many of these airports are not located in the cities that
they supposedly represent (
Data
sets thus not only vary geographically, but they cover varying periods of
time. NOAA puts out “normals”
for each 30-year period ending in zero (the latest is for the period of 1971 to
2000). The weather data in each “normal”
differ from the ones before it and the ones after it. Which numbers are “official”, then? The answer is that they all are.
What
I do is to gather together as many of these sets of data as I can get my hands
on. (I might add that forty years of
data collection has given me quite a library of data.) Each data set is then given a weight that
represents my professional judgment as to how much influence that particular
set will have in the final numbers that you see in each Guide. The computer program that I wrote then chews
all of these weights and numbers up and generates a unique data set that
embodies my professional perspective. I
then use this data set to write the Guides.
In
short, then, the Guides are not facts, they are opinion—my
own professional opinion, but opinion nonetheless. They are not histories, they are forecasts—and
like all forecasts, they are subject to error.
Will the actual weather differ significantly from the numbers in my Guides? You bet it will—on pmr
occasion or another. These guides can’t
tell you all of the weather that can happen, they only tell you what I believe
is the most likely weather for that month and for that area.
If
you are planning months ahead, then I believe that they are the best weather
guides that you can get. If you are
leaving today, then you might want to check the current forecasts for your
destination. These forecasts are
available from a large number of sources.