Hurricanes are violent storms that cause millions of dollars in property damage and take many lives. They can be extremely dangerous, and too often people underestimate their fury.  Hurricanes normally originate as a small area of thunderstorms over the Atlantic Ocean west of the Cape Verde Islands during August or September. For several days, the area of the storm increases and the air pressure falls slowly. A center of low pressure forms, and winds begin to whirl around it. It is blown westward, increasing in size and strength.  Hurricane hunters then fly out to the storm in order to determine its size and intensity and to track its direction. They drop instruments for recording temperature, air pressure, and humidity (湿度), into the storm. They also look at the size of waves on the ocean, the clouds, and the eye of the storm. The eye is a region of relative calm and clear skies in the center of the hurricane. People often lose their lives by leaving shelter when the eye has arrived, only to be caught in tremendous winds again when the eye has passed.  once the forecasters have determined that it is likely the hurricane will reach shore, they issue a hurricane watch for a large, general area that may be in the path of the storm. Later, when the probable point of landfall is clearer, they will issue a hurricane warning for a somewhat more limited area. People in these areas are wise to stock up on nonperishable foods, flash light and radio batteries, candles, and other items they may need if electricity and water are not available after the stoma. They should also try to hurricane-proof their houses by bringing in light-weight furniture and other items from outside and covering windows. People living in low-lying areas are wise to evacuate their houses because of the storm surge, which is a large rush of water that may come ashore with the storm. Hurricanes generally lose power slowly while traveling over land, but many move out to sea, gather up force again, and return to land. As they move toward the north, they generally lose their identity as hurricanes.The eye of the hurricane is ______ .