What indicates that a tropical cyclone can be expected at your position within 24 to 48 hours?

A
A daily fluctuation of over 6 millibars in the barometric reading
B
A sudden wind shift from southwest to northwest followed by steadily increasing winds
C
The normal swell pattern becoming confused, with the length of the swell increasing
D
An overcast sky with steadily increasing rain from nimbostratus clouds
E