ENSEMBLE GLOBAL OCEAN WAVE FORECAST SYSTEM (EGOWaFS)

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ENSEMBLE GLOBAL OCEAN WAVE FORECAST SYSTEM
(EGOWaFS)
NOAA THORPEX PI WORKSHOP, 01/(17-19)/ 2006 at
NCEP, Camp Springs, MD
H. S. Chen NOAA/NCEP/MMAB
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1. Introduction.

• Meteorological Forecast System (FS ) vs. Ocean
  Wave FS.
• Chaotically nonlinear vs. weakly nonlinear,
  Initial condition impact,
• NCEP ocean wave model, NWW3
• Directional, spectral wave model,
• http//polar.ncep.noaa.gov/waves

2. Ensemble Global Ocean Wave FS (EGOWaFS).
3. Some results and remarks.
4. Experimental website ftp-site for EGOWaFS.
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1. Introduction.
Initial Condition
Meteorological FS

• chaotically nonlinear,
• the butterfly effect.

Initial Condition
Sea surface forecast wind
Ocean Wave FS
- weakly nonlinear,
- highly dissipative.
Forecast wave field
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  Figure 1.1 A
schematic illustration of the growth of an
isopleth of the forecast error probability
distribution function, from (a) initial phase,
to (b) linear growth phase, to (c) nonlinear
growth phase, to (d) loss of predictability.
(borrow from ???)
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Remark
Perturbation of the initial wave field has
little impact on the wave forecasts except in the
first 24 forecast hours and prominently, the
wind forcing dominate the wave field throughout
the forecast period.
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2. Ensemble Global Ocean Wave FS (EGOWaFS).
- 10 ensemble wind fields 1 control wind field
(operational),

- NWW3 wave model,
- 10 ensemble wave fields 1 control wave field
(operational).
- Ensemble products Ens Mean, Ens Spread and Ens
Probability.
- 84 hours forecast, longer in the future.
- Parallel run since 12/2004. Operational
(target) 03/2006.
- use a considerable amount of computer resource.
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3. Results and Remarks.

Wind and wave data of about 30 buoys of deep
water (mostly NDBC buoys) in the months of May
through July, 2004 are used for comparisons.
Only June are presented here.

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Green thin lines ensembles, Red
dash line with sign control, Blue line with
sign ensemble mean Black dot with o
sign observed data.
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Remarks
The ensemble FS is more reliable and realistic
than the deterministic FS.
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More works need to be done.
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4. Experimental Website and ftp-site
http//www.emc.ncep.noaa.gov/projects/wd21hc/ensem
b/
ftp//polar.ncep.noaa.gov/pub/waves/test_hsc/ensem
b_fd
Plot illustrations

• Spaghetti Plot.
• Mean and Spread Plot.
• Probability Plot.

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