User:Inks.LWC/Sandbox3

A rapidly falling atmospheric pressure is possible due to strong upper level forces on the system, and when pressures fall more than 1 millibar (0.029 inHg) per hour, such a cyclone is sometimes referred to as a bomb. These bombs rapidly drop in pressure to below 980 millibars (28.94 inHg) under favorable conditions such as near a natural temperature gradient like the Gulf Stream, or at a preferred quadrant of an upper level jet streak, where upper level divergence is best. The stronger the upper level divergence over the cyclone, the deeper the cyclone can become. Hurricane-force extratropical cyclones are most likely to form in the northern Atlantic and northern Pacific oceans in the months of December and January. On 14 and 15 December 1986, an extratropical cyclone near Iceland deepened to below 920 hPa, which is a pressure equivalent to a category 5 hurricane. In the Arctic, the average pressure for cyclones is 988 millibars (29.18 inHg) during the winter, and 1,000 millibars (29.53 inHg) during the summer.