Back to Tropical Cyclones
Forecasting Page | Back
to Main FAQ Page
Subject: F2) What are those track and intensity
models that the Atlantic forecasters are talking about in the
hurricane and tropical storm Discussions?
Contributed by Sim Aberson
A variety of hurricane track forecast models are run operationally
for the Atlantic hurricane basin:
- The basic model that is used as a "no-skill" forecast to compare
other models against is CLIPER (CLImatology and PERsistence),
which is a multiple regression statistical model that best
utilizes the persistence of the current motion and also
incorporates climatological track information
(Aberson 1998). Surprisingly, CLIPER was difficult
to beat with numerical model forecasts until the 1980s.
- A statistical-dynamical model, NHC90
(McAdie 1991), uses geopotential height predictors
from the Aviation model to produce a track forecast four times
per day. The primary synoptic time NHC90 forecasts (00 and 12
UTC) are based upon 12 h old Aviation runs. A special version
of NHC90, NHC90-LATE, is run at primary synoptic times with the
current Aviation run, and is available a number of hours after
NHC90. Both versions of NHC90 have been run operationally since
1990. An update to this model, NHC98, was implemented in 1998.
- The Beta and Advection Model (BAM), follows a
trajectory in the pressure-weighted vertically-averaged
horizontal wind from the Aviation model beginning at the
current storm location, with a correction that accounts for the
beta effect (Marks 1992).
Three versions of this model, one with a shallow-layer (BAMS),
one with a medium-layer (BAMM), and one with a deep-layer
(BAMD), are run. BAMS runs using the 850-700 mb layer,BAMM
with the 850-400 mb layer, and BAMD with the 850-200 mb layer.
The deep-layer version was run operationally for primary
synoptic times in 1989; all three versions have been run four
times per day since 1990.
- A nested barotropic hurricane track forecast model
(VICBAR) has been run four times daily since 1989. The
primary synoptic time runs are run from current NCEP analyses,
the off-time runs are run from six hour old data
(Aberson and DeMaria 1994). Another barotropic model,
LBAR, for Limited-Area Barotropic Model, is also being run
operationally every 6 hours which performs slightly worse than
VICBAR, but is available earlier for use by the NHC forecasters.
- The NCEP Aviation and MRF models
(Lord 1993) has been used for track forecasting since
the 1992 hurricane season. These are global models.
- A triply-nested movable mesh primitive equation model developed at
the Geophysical Fluid Dynamics Laboratory
(Bender et al 1993), known as the GFDL model,
has provided forecasts since the 1992 hurricane season.
- The United Kingdom Meterological Office's global model
(UKMET) is utilized for forecasting the track of tropical
cyclones around the world (Radford
1994). The OAR starting receiving
these operationally during 1996.
- The United States Navy Operational Global Atmospheric
Prediction Systems (NOGAPS) is also a global numerical model
that shows skill in forecasting tropical cyclone track
(Fiorino et al. 1993). This
model was also first received operationally at the National
Hurricane Center during 1996.
Despite the variety of hurricane track forecast models, there are
only a few models that forecast intensity change for the Atlantic
basin:
- Similar to the CLIPER track model, the SHIFOR
(Statistical Hurricane Intensity Forecast model) is
used as a "no-skill" intensity change forecast. It is a
multiple regression statistical model that best utilizes the
persistence of the intensity trends and also incorporates
climatological intensity change information
(Jarvinen and Neumann 1979). SHIFOR has been
difficult to exceed until recent years.
- A statistical-synoptic model, SHIPS (Statistical
Hurricane Intensity Prediction Scheme ), has been available
to the OAR since the mid-1990s
(DeMaria and Kaplan 1994).
It takes current and forecasted information on the synoptic scale
on the sea surface temperatures, vertical shear, moist stability,
etc. with an optimal combination of the trends in the cyclone
intensity.
- The GFDL model, described above in the track
forecasting models, also issues forecasts of intensity change
for the OAR.
- A new statistical scheme for estimating the probability of
rapid intensification has been developed (Kaplan and DeMaria 2002)
and is now being used operationally. The RI scheme employs
synoptic and persistence information from the SHIPS model to
estimate the probability of rapid intensification (24 h increase
in maximum wind of 35 mph or greater) every 6 hours.
Back to Tropical Cyclones
Forecasting Page | Back
to Main FAQ Page
|