The Navy's Numerical Hurricane and Typhoon Forecast Scheme: Application to 1967 Atlantic Storm Data
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Authors
Renard, Robert J.
Levings, William H.
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Advisors
Date of Issue
1969-10
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Abstract
Renard recently reported (Monthly Weather Revie:w, July 1968) on the development of a numerical scheme
for predicting the motion of tropical storms for periods up to three days. An extension of the forecast scheme,
as presented here, may be described as a two-step process. First, numerical geostrophic steering of the cyclone
center is accomplished using Fleet Numerical Weather Central's analyses and prognoses of smoothed isobaric
height fields, called SR fields. Next, a statistical correction for vector bias in the numerical steering computation
is used selectively in an attempt to enhance the accuracy of the forecast track of the storm. The
bias modification is dependent solely on the peculiarities of recent history 12- and 24-hr forecasts in relation
to the storm's actual trajectory. Forecasts for intervals up to 72 hr, generated from 1967 Atlantic operational
storm positions, are compared to results from the previous experimental forecasts for 1965 using best-track
positions of Atlantic storms. ยท
Results indicate that the numerical scheme shows skill in relation to the official forecast accuracy for both
1965 and 1967, as documented by Fleet Weather Facility, Jacksonville, Fla. In 1967, the average relative
improvement over official forecasts, using 700-mb prognostic SR fields for steering, ranges from 52% for
12-hr forecasts (90 cases) to 9% for the 48-hr estimates (129 cases).
The paper includes a discussion of various forecast modes and selective modification schemes as well as
stratification of error statistics by geographical area, storm track and stage.
Type
Description
The article of record as published may be found at http://dx.doi.org/10.1175/1520-0450(1969)008<0717:TNNHAT>2.0.CO;2
Series/Report No
Department
Meteorology
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NPS Report Number
Sponsors
Research financially supported by the Navy Weather Research
Facility, Norfolk, Va.
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Citation
Journal of Applied Meteorology, Volume 8, No. 5, October 1969.