How Historic Was Hurricane Michael Really? (Photo Credit: The Weather Channel and the National Hurricane Center)
DISCUSSION: Earlier this month, on October 10, 2018, Hurricane Michael made landfall along the Panhandle of Florida, over the city of Mexico Beach. Michael made landfall as a strong Category 4 storm, with maximum sustained winds of 155 mph. In addition to the strong winds, Hurricane Michael’s central pressure was exceptionally low, at 919 mb. The winds, combined with storm surge as high as 12 feet in some areas, lead to devastating destruction of land and property along the path of the hurricane. Due to all of this, Hurricane Michael is already being called a historical event, but just how rare is an event like Hurricane Michael.
For starters, it is rare for a hurricane to make landfall in the continental United States as a Category 4 or greater. Since 1851 there have only been 27 hurricanes to do so, with the greatest number making landfall over Florida, as can be seen in the image above. However, despite this, since the United States began keeping a record of hurricanes there has never been a Category 4 or 5 hurricane to make landfall along the Florida panhandle. Therefore, the location that Michael made landfall by itself makes it historic.
Aside from its location, it was also the first hurricane to make landfall in the United States in the month of October as a Category 4 or higher storm since Hurricane Hazel 64 years ago. Hurricane Hazel was a Category 4 hurricane when it made landfall near the border of North Carolina and South Carolina on October 15, 1954. Its estimated maximum winds were between 130 mph and 150 mph and had storm surge that reached 18 feet along portions of North Carolina. The storm then moved northward into Canada, where it dropped 11 inches of rainfall in Toronto.
Hurricane Michael’s minimum central pressure also makes it unique. Since 1851 there have only been two storms, The Florida Keys Labor Day Storm in 1935 and Hurricane Camille in 1969, that had a lower central pressure at landfall. The Labor Day storm made landfall as a Category 5 storm with a central pressure of 892 mb in the Florida Keys. It then turned to the northeast and made a second landfall as a Category 2 storm near Cedar Key Florida. Hurricane Camille was also a Category 5 when it made landfall along the Mississippi coast with a central pressure of 900 mb. Its maximum wind speed was not recorded because the wind instruments in the path of the storm were destroyed but winds along the coast were estimated to be 200 mph. Hurricane Michael also beat Hurricane Katrina’s minimum central pressure which was 920 mb, though not by much. Katrina, which devastated New Orleans in 2005, had been a Category 5 storm with a minimum pressure of 902mb the day before landfall but at the time of landfall on Aug 29 it had weakened to a Category 3 and its minimum pressure increased.
The location, time of year, and the minimum central pressure of the Hurricane Michael for sure make it an historical event. However, these factors alone will likely not be the only reasons Hurricane Michael will live in infamy. In the following weeks, months, and years we will continue to examine the storm and likely find other factors that will add to the historic nature of this event. Even more, we do not know the economic impact the storm had, and the amount of property and loved ones lost.
Additional information about memorable hurricanes to hit the US can be found at: https://www.nhc.noaa.gov/outreach/history/
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© 2018 Meteorologist Sarah Trojniak
Inside Edge on What Helped Hurricane Michael to Rapidly Intensify Leading up to Landfall. (Imagery credit: Meteorologist Stu Ostro)
DISCUSSION: There is no question that Hurricane Michael shocked the state of Florida and the rest of the world for that matter on the morning of October 10th, 2018. It goes without saying that Hurricane Michael will undoubtedly go down in history as one of the top five most intense hurricanes to make a direct hit on the contiguous United States as far back as records go. Having said that, it is even more interesting to learn more about and why Hurricane Michael managed to intensify so quickly and so close to the official point of landfall in northeast Florida as this system did. This is complicated and yet, at the same time represents a perfect example of a classic tropical cyclone intensification scenario.
To get into the factors which went into how and why Hurricane Michael intensified as quickly and abruptly just before its landfall near Mexico Beach, Florida, there are some atmospheric and environmental fundamentals which must exist. It is imperative to establish the fact that for a hurricane to intensify and/or rapidly intensify at any point in time, there must always be sufficiently warm sea-surface temperatures in place both under and out ahead of an approaching tropical cyclone. In the case of Hurricane Michael, there was more than sufficiently warm sea-surface temperatures spread across the northeastern Gulf of Mexico out ahead of the forward approach of Hurricane Michael. Hence, the first major piece was most certainly in place for this tropical cyclone.
The second major environmental factor which is key and essential for tropical cyclone intensification is the presence of little to no vertical wind shear both surrounding the immediate location of the intensifying tropical cyclone and out ahead of the given tropical cyclone. In the case of Hurricane Michael, the main concern regarding the presence of vertical wind shear was when this system was developing both near and just to the north of the Yucatan Peninsula in eastern Mexico. However, as this storm continued to move northward with time, the issues pertaining to the presence of vertical wind shear subsided rather quickly as the storm’s inner and outer core organized rather quickly with time which limited the vertical wind shear threat and concerns thereof. Thus, the second piece of the puzzle was most certainly in place for then intensification of Hurricane Michael.
The third major piece which is important and is critical both ahead and during a period of intensification and/or rapid intensification of a tropical cyclone is to have an effective and consistent outflow channel both surrounding and out ahead of a strengthening tropical cyclone. This consistent outflow surrounding an intensifying tropical cyclone is important since this allows a tropical cyclone to vent all the excess “cloud debris” and excess heat energy which is always being released both above and surrounding the convective inner and outer portions of a developing and/or mature tropical cyclone. As shown in the animated graphic attached above, there was most certainly an effective outflow channel in place with Hurricane Michael which allowed for this outflow channel to be maintained incredibly well with Michael right up to the point of landfall.
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: The Global Precipitation Measurement (GPM) Core Satellite was launched in 2014 as a joint project between NASA and the Japan Aerospace and Exploration Agency (JAXA). The two primary instruments carried on the satellite are the GPM Microwave Imager and the Dual-Frequency Precipitation Radar (DPR). The GMI measures naturally emitted radiation in 13 channels, while the DPR measures scattered radiation at two microwave frequencies. The combination of information from these instruments provides critical information necessary to create a globally-consistent measure of precipitation. Rain gauges and ground-based radar are useful tools for estimating precipitation, but these are only available on land and coverage is not uniform. Only from a satellite can a truly consistent, global measure of precipitation be obtained. The GPM mission actually consists of a constellation of satellites, but the GPM Core Satellite provides the basis against which all the other satellite instruments are compared or calibrated against.
Hurricane Walaka is currently a Category 1 hurricane located northwest of Hawaii. The storm formed southwest of Hawaii and moved west of the islands without any direct impacts there. The storm is currently weakening as it moves over cooler water and into the mid-latitude westerlies. When the storm was still an intensifying tropical storm on 30 September, the GPM satellite passed over the storm center. The above figure shows a 3-D depiction of the 17-dBZ surface from the Ku Band of the DPR instrument. This basically shows how the precipitation is distributed around the storm and in the vertical. The figure also shows the intense and deep (up to 8.5 miles [13.7 km] above the sea surface) convection in the southeastern and northwestern section of the eyewall of the storm. The DPR also observed intense rainfall in a rainband northeast of the storm center with an estimated rain rate of nearly 6.5 inches (165 mm) per hour. Without satellite microwave instruments, acquiring estimates of such intense rainfall in the middle of the ocean would be much more difficult if not impossible.
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© 2018 Meteorologist Dr. Ken Leppert II