Track & Intensity Forecasting Flashcards
Tropical Cyclone Motion
“A cork in a stream”
Problem with Tropical Cyclone Motion
The “Stream Flow” or steering currents are not static, they are dynamic or always changing
To a first- order approximation TC motion is governed by
Conservation of relative vorticity
How does the vortex move
With the large-scale steering flow
If a circulation has positive absolute angular momentum and it converges or contracts (diverges or expands) the it________ (slower) in the __________(negative)_________, and it will _______(lose) __________ absolute_______.
Must spin faster, positive, direction, gain, cyclonic, vorticity
Do changes in TC inner-core structure have any influence on the future track?
No there’s little influence
The Beta Effect or Beta Drift……..
Induces steering of 2-4 kt to the northwest
The circulation of a TC, combined with the North-South variation of the Coriolis parameter, induces asymmetries know as Beta Gyres. These Beta Gyres produce a net steering current across the TC generally toward the northwest at a few knots
Beta Drift or Beta Effect
Climatology and Persistence Model (CLIPER)
No longer provides useful operational guidance, but is used as a benchmark for other models and the official forecast. If a model has a lower mean errors than CLIPER it is said to be ‘skillful’
The Beta and Advection Model (BAM): A class of simple _______ that utilize vertically averaged horizontal winds from the GFS to compute TC Trajectories. These trajectories include a ________ to account for the _____ of the earth’s __________(beta advection)
Trajectory models, correction term, impact
BAM medium or BAMM/TABM (840-400 mb)
Default track model in the SHIPS intensity forecast model
Global Models have _______________ to define the TC ___________ (eye and eye wall structure)
(Inner-core changes have virtually no effect on track)
Inadequate resolution, inner core
Global models have no ___________conditions an therefore should have better ________ at longer ranges than the limites-area models
Lateral boundary, performance
Limited-Area (Regional) models performance _________ at ________ ranges
Degrades, longer
There is a ________ difference between _________ and __________ forecasts
HUGE, landfall, non-landfall
The 2022 hurricane season was _____ than _____ to forecast at 96 and 120 h due ro the 2022 CLIPER5 errors being ________ than ______
Easier, average, lower, average
Since 2016, NHC track forecast track errors……..
Have not changed
Since 2016, NHC track forecast skill has basically
Not changed
The ______(weaker) the TC, the ______ (worse) are NHC’s track forecasts at _____________
Stronger, better, all forecast times
Often the _________ models are __________ formed from an ensemble of good performing _________ models
Most successful, consensus aids, individual
Dynamical model consensus is an excellent……
First guess
Continuity dictates that it must be considered in…….
The view of previous official forecasts
Try to asses what so that you can understand and perhaps evaluate the model solutions?
Steering influences
Compare the models’ ________ of the environments features, not just the __________
Forecast, TC tracks
Evaluate the _________ of the ____ in the model fields. Unrealistic TC can affect the ______ of a successful forecast.
Initialization, TC, likelihood
Spread of ______ can dictate forecaster ________
Models, confidence
Sometimes the forecaster might want to exclude certain models from a “selective consensus”……. If _________ amoung the models can be ________
Discrepancies, resolved
Previous official forecast exerts a strong _______ on the current forecast
Constraint
NO_________(1)
Windshield Wipering
NO…..(2)
Tromboning
‘Smart’ models have to _______ during the course of a new seasons and, thus, can be _________early
Re-learn, unreliable
Accurate estimate of ________ and _____ is extremely important
Initial location, motion
TC forecasters ________ and _________ these wobbles in order to mitigate large track forecasts errors
Must anticipate, smooth through
Initial motion estimates should ____ reflect ______ track wobbles that will not persist
Not, short-term
NHC philosophy is that it is better to ___ events a little bit than to be going ________ with analyses of forecasts
Lag, back and forth
Intensity Output initial conditions: tropopause:
-70 deg C
Minimum attainable surface pressure (mb) as a function of surface air temp (Ts) and weighted mean outflow temperature (Tout) assuming ambient surface pressure of 1015 mb, ambient surface RH of 80% 20 deg latitude, outer radius of 500 km and __________
No vertical wind shear
The _____ the ______ temperature and the ____ the surface _______ temperature the _________ a hurricane can become
Colder, outflow, warmer, inflow, more intense
We can only sample a _____ of the TC each observation has strengths and weaknesses we want a value that is __________ of the TC’s mean circulation
Part, representative
Always weigh the more accurate _______ data over remotely sensed data
In situ
Sea Surface Temperatures: _______(cool) SSTs generally produce _______(weaker) hurricanes
Warm, stronger
Ocean Heat Content: the greater the depth, more available heat can be potentially converted to energy and also_________
Prevent cold upwelling
_______ in the low-levels results in a ________ and ________
Drier Air, Higher LCL, Higher LFC
If lifting mechanism is weak, then low-level air parcels may not reach the LFC and release the conditional instability resulting in ___________
No deep convection
Tropical cyclone intensity change can be caused by inner-core processes such as
Eyewall replacement cycles (ERC) or concentric eyewalls
In major hurricanes, we often see an _________ eye wall occur at larger distances from the center than the radius of the original eye wall
Outer concentric
The occurrence of ERC’s appears to be at least partly related to the _______ and _______(RMW)
Hurricane’s intensity, radius of maximum winds
The more intense hurricane and smaller the RMW, the more likely that an ERC will occur; this is due to ________ winds in the ________ flowing ______
Supergradient, inner eye wall, outward
When this outer eye wall becomes ________, weakening ________ occurs
Dominant, invariably
Winds weaken over land due to lack of………
Latent heat and increased friction
Terrain and Higher Elevations: These wind speeds are not considered to be
Representative of a TC’s actual tangential winds
SHIPS forecasts are _______ to interpret
Easier
Experimental tests using GOES lightning in the _________ in RII show improved skill
Inner-core region
Lightning is a _____ for ____ strength owing to lightning generation mechanisms
Proxy, updrafts
Problems with representation of shear; regional models such as HWRF, HMON, HAFS-A/-B models are
To shear resistant
Dynamic models are more _______ for basin-wide ______ forecasts
Skillful, intensity
Statistical methods more _______ skillful for identifying ________
Generally, RI cases
Extreme events are almost
Never forecasted
