A PROCEDURE OF SHORT-RANGE WEATHER FORECASTING 785 
tuitiveness of the forecaster and depends largely upon 
his experienced insight in perceiving and anticipating 
the nonadvective (and diabatic) processes in the at- 
menting the advective-adiabatic extrapolation of the layer 
isentropes wilh physical considerations regarding the 
nonadvective and diabatic contributions to their future 
——— MEAN JANUARY 
SEA SURFACE 
ISOTHERMS 
3 
a 
—@ MEAN ICE 
LIMIT 
JANUARY 
— 1000 MB FRONTS, —— 1000 MB ISOHYPSES (gpOm), [i] PRECIPITATION, [|] As—Ns 
------ NONADVECTIVE 500/1000 MB ISALLOHYPSES FOR THE PAST 24 HR (gpOm) 
Fig. 8a 
ISOHYPSES (gpDm) 
500 MB FRONTS 500/1000 MB 
O SUCCESSIVE I12-HR POSITIONS OF LOW IN 500/1000 MB HYPSOGRAPHY 
Fic. 8) 
Fie. 8.—Maps for 1500 GMT, January 5, 1949, showing the relation of the nonadvective 500/1000-mb allohypsography for the 
past 24 hr to (a) the 1000-mb and 500/1000-mb hypsographies, (6) the areas of precipitation and altostratus-nimbostratus, (c) 
the extent of snow cover, (d) the sea surface temperature, and (e) the pertinent orography. This allohypsography has been based 
on streamline maps at 6-hr intervals, and instantaneous values of the isobarically geostrophic advective change in the relative height 
computed from the statical-kinematical tendency equation. (See [33], equation 11-61(1).) 
displacement. We choose an appropriately idealized 
prognostic pattern of the nonadvective relative allo- 
hypsography for (t) + 24") — t. Whereas the ad- 
vective-adiabatic extrapolation in stage four is mainly 
mechanical in its application, this prognosis, on the 
other hand, brings into play the creativeness and in- 
mosphere and in evaluating their effect upon relative- 
height change. The rational separation of the prognosis 
into its mechanical and nonmechanical operations 
(viz., stages four and five), in addition to concen- 
trating the forecaster’s efforts in a routine way on 
these more or less intangible processes and the asso- 
