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HOME >
Outlooks >
Monthly to Seasonal Outlooks >
Probability of Exceedance Forecast >
Outlooks for major Cities
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This experimental outlook product gives the probability that a
temperature or precipitation quantity will be exceeded at the location in question, for the given season at the given lead time. The locations
are one of 102 forecast divisions in the mainland U.S., or an individual station in other regions.
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CPC Outlooks for Major U.S. Cities
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Forecast Distribution File
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File Names
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cpcctytd.dat
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- Temperature Distribution file for most recent month
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cpcctyhdd.dat
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- Heating degree day Distribution file for most recent month
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cpcctycdd.dat
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- Cooling degree day Distribution file for most recent month
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Description
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These tables give the climate outlook for 50 of the largest metropolitan areas in the
U.S., with a few other cities included to provide even coverage. The tables give the
forecast and climatological mean, and the exceedence threshold values for given
probability levels. (98,95,90,80,70,60,50,40,30,20,10,5, and 2 percentile levels).The forecasts are
for specific airport observation sites listed in the file: citydict.txt.
Note that forecasts for Grand Rapids MI, Kansas City, MO, New Orleans, LA, Orlando FL,
and Pittsburgh, PA, are for the metropolitan area averages, since the airport at
these sites had data problems that prevented the derivation of a relationship between
the CPC forecast division and the airport (Usually due to a change in airport location).
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Derivation
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These data are derived from the outlooks issued monthly by CPC. Details
of the relationships between each city and the CPC forecast division in which
it resides, as well other information on the urban area temperatures
can be found by following this link
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Contents
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The forecasts issued on a particular month are grouped together. There are 2 header
records followed by multiple data records (Rows) per monthly forecast. Forecasts are for
three month target seasons, defined by forecast issue time and lead.
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The first line on the header record gives the month, day and year (mmdd yyyy) of
forecast issue time, followed by the number of groups and the number of forecast locations
in each group. The final number is a forecast type id flag. 950 is a number assigned to
identify seasonal temperature forecasts, 962 identifies seasonal heating degree day forecasts,
and 963 identifies cooling degree day forecasts.
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The second header label gives column definitions. Each forecast issue time has its own
2 line header record.
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Column: |
label: |
Definition |
1-2: |
year mn |
Year and month number
that the outlook was issued. 1=Jan, 2=Feb. Forecasts are issued around mid-month. |
3: |
lead |
Approximate lead time of
forecast in months - rounded upward, An actual lead time of about one-half month (the
shortest lead on the outlook) is rounded to lead=1, for example. The valid target season
can be found by adding lead months to the initial time listed in column 1 and 2, adjusting
for year changes. |
4: |
cd: |
The forecast location to
which data apply. See citydict.txt for definitions. |
5-17: |
98,95,90,etc |
Values (Temperatures, or
degree days) expected
(Forecast) to be exceeded by the percent of time listed in the column label. |
18: |
F mean: |
The forecast mean value
for the target period. |
19: |
C mean: |
The climatological mean
value. |
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Data Set Use
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These data are designed to be used in quantitative analysis of CPC forecasts. The
forecasts are only estimates of the distribution implied by the long lead outlooks and are
derived from the tercile probability anomalies (Forecasts for above, near, and below
median). The distribution is most accurate in the vicinity of these tercile boundaries (33
and 66 percent probability of exceedence). Particular caution should be used in the
interpretation probabilities below about 10% or above 90%.
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Acknowledgements
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This project is supported by Risk Prediction Initiative (www.bbsr.edu/rpi/rpihome.html)
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