Table IV 



Summary of Quantities to be Determined when Forecasting Sv/ell 

 In the Absence of Following or Opposing Winds 



No. 



1 



2 

 3 

 4 

 5 



Term 



Generating area, mean distance 

 between Isobars drawn at inter- 

 nals of 5 mb 



Mean latitude 



Curvature of isobars 



Geostrophic wind 



Wind velocity at sea surface 



Symbol Units 

 G 



Source 



U 



(U) 

 F 



*d 



t . 



min 



6 Average wind velocity 



7 Observed wind at sea surface 



8 Fetch 



9 Duration of wind 



10 Minimum duration 



11 Wave height at end of fetch 



12 Wave period at end of fetch 



13 ■ Distance of decay 



lU Reduction factor for wave height H„/H-p 



15 Wave height near coast 



16 Factor of period increase 



17 Period near coast 



18 Travel time 



19 Wave length 



20 Wave velocity 



Degrees 



of 



latitude 



Degrees 



Knots 

 Knots 



Knots 



Synoptic chart 



Synoptic chart 



Synoptic chart 



Tables or graph 



From (4), considering curvature 

 of isobars. Multiply by: 

 0.60 Great cycl. ourv. 

 0.63 Small cycl. curv. 

 0.65 Straight Isobars 

 0.67 Small antlcycl. curv. 

 0.70 Great antlcycl. curv. 



Current and preceding synoptic 

 charts 



Beaufort Synoptic chart 

 Naut . m. Synoptic chart' 



Hours 



Hours 



Feet 

 Seconds 



Naut . m. 

 Feet 



Current and preceding synoptic 

 charts 



] 



Plate I 



Plate II or III, using (6) and 

 (8) If t(3 >t ^n; Plate IV or V, 

 using (6) and (9) if t^ -^tmin 



Synoptic charts 



Plate VI, using (12) and (13) 



(11) times (14) 



Plate VI, Inset II, using (I4) 



(12) times (16) 



Plate VI, using (12) and (13) 

 Plate VI, Inset I, using (17) 

 Plate VI, Inset I, using (17) 



39 



