Reason: As shown in the figure, passing through AD⊥BC where point A is point D.

Then AD is the shortest distance from the city to the typhoon center.

In Rt△ABD, because ∠ B = 30, AB=240. ..

∴

AD=

12AB=

12×240= 120

(km)

According to the topic, when it is within the typhoon center (12-4)×25=200 (km), it will be affected by the typhoon.

Because 120 < 200, the city will be affected by the "three pa".

(2) According to the question (1), when point A is less than 200 kilometers away from the typhoon center, it will be affected by the typhoon, so mark AE = AF = 200 on BC. When the typhoon center moves from point E to point F, the city will be within the influence range of the typhoon (as shown in the figure).

From Pythagorean theorem,

DE=

AE2-AD2=

2002- 1202= 160

(km)

So EF=2× 160=320 (km).

It is also known that downtown Sao Paulo is moving at a speed of 20 kilometers per hour.

So the typhoon affects the city for 320÷20= 16 (hours).

(3)∵AD is closest to the typhoon center,

The maximum wind force of this typhoon in this city: 12-( 120÷25)=7.2 (level).

Affected by the typhoon, the maximum wind force in this city is 7.2.