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12.3: Air pressure vs. intensity for Hurricane Michael

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    Winds and air pressure in a hurricane

    The primary cause of a hurricane’s intense winds is changes in the minimum surface air pressure in the eye of the storm. As the minimum surface pressure declines, the pressure difference between the hurricane's center and its periphery increases. Recall from Investigation 7 that a bigger difference in pressure results in a stronger pressure gradient force, hence a stronger wind. As the minimum central pressure within Hurricane Michael decreases, wind speeds should naturally increase. We can investigate both Michael's minimum central pressure and wind speed to highlight this. Figure 12.3.1 shows maximum sustained wind speeds (blue line, left Y axis) and air pressure (orange line, right Y axis) vs. time (UTC).

    Graph of wind speed and central air pressure for Hurricane Michael. Details in caption.
    Figure \(\PageIndex{1}\): Plot of air pressure and wind versus time for Hurricane Michael. (Public Domain; Alicia Mullens). Alternative description of the image. 
    1. Between 21Z on October 6th and 15Z on October 10th, the minimum air pressure of Michael (the orange line) generally:
      1. Increased   
      2. Declined
    2. On the other hand, during the same time period, maximum wind speeds in the storm generally:
      1. Increased   
      2. Declined
    3. After 15Z on October 10th, the air pressure:
      1. Increased
      2. Stayed the same
      3. Decreased
    4. During the same period, the maximum wind speeds in the storm:
      1. Increased   
      2. Stayed the same   
      3. Decreased
    5. Based on this information, we can say that, in general, as air pressure declines
      1. Wind speed increases
      2. Wind speed also decreases
    6. The time (15Z on October 10th) from the previous three questions is approximately 10 am on October 10th, which ____________ with the time that Michael was forecast to make landfall in Florida. 
      1. coincides
      2. does not coincide
    7. Thus, the weakening of Hurricane Michael was likely caused by: 
      1. Making landfall and losing access to warm ocean waters
      2. A sudden increase in wind shear
      3. Neither of these
    8. The weakening was:
      1. Faster than the strengthening
      2. Slower than the strengthening. 

    This page titled 12.3: Air pressure vs. intensity for Hurricane Michael is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Neel Desai & Alicia Mullens.