41. It is traditionally expressed either in metres or as a pressure difference in hectopascal ( hPa, equivalent to millibar ). 42. :The limit for human life ( with considerable difficulty ) is a partial pressure of about 65 millibars of O2. 43. Surface pressures varied diurnally over a 0.2 millibar range, but showed 2 daily minima and two daily maxima. 44. This effect is strongest in tropical zones, with an amplitude of a few millibars , and almost zero in polar areas. 45. What contributed to the event, was the strong high pressure system ( about 1040 millibars the morning of the 16th ). 46. The average January sea level pressure at its centre is about 1, 020 millibars ( 30.12 inches of mercury ). 47. The lowest pressure of this storm was 918 millibars , lower than that of some Category 5's, such as Guillermo. 48. The hurricane reached a peak intensity of 90 mph ( 140 km / h ) and its barometric pressure dropped to 979 millibars . 49. As central pressures go, this was not particularly a powerful system; it was only 996 millibars the morning of the 17th. 50. The bar and the millibar were introduced by the Norwegian meteorologist Bjerknes, who was a founder of the modern practice of weather forecasting.
