Hurricane Michael Breaks Records!

Hurricane Michael Nearing Landfall on October 10, 2018  (Source: WUSA9)

Hurricane Michael quickly developed into an intense borderline Category 4/Category 5 storm with sustained winds of 155 mph at its time of landfall yesterday.  Its minimum central air pressure fell to 919 millibars (standard sea level air pressure is approximately 1013 millibars or “mb”).  That means Michael had the third lowest air pressure of any landfalling hurricane in the United States and the fourth highest sustained winds speeds.  Michael became the strongest hurricane to ever make landfall in the Florida panhandle.  

Only three major Category 3 hurricanes (sustained winds of 111 – 129 mph) have made landfall in the Florida panhandle since 1950.  However, the Gulf Coast and inland areas are significantly more developed now than they were during past storms, making the potential for damage with Hurricane Michael significantly higher.  The three previous hurricanes (Dennis 2005, Opal 1995 and Eloise 1975) each caused enough damage to have their names subsequently retired by the World Meteorological Organization (WMO).

 

Unlike Dennis, Opal and Eloise that all weakened before making landfall, Hurricane Michael continued to intensify.  From the time Michael became a hurricane on Monday, October 8 at 11:00 a.m. (Eastern) with sustained winds of 75 mph and a minimum air central air pressure of 982 mb, it continued to intensify over the next 51 hours until it made landfall at 2:00 p.m. Eastern time October 10 with sustained winds of 155 mph and a minimum central air pressure of 919 mb.  A drop of 63 millibars and increase of 80 mph in just over 48 hours is a relatively fast rate of intensification. 

Its rapid strengthening is an important consideration since the evacuation zone for a Category 4 hurricane is much larger than for a Category 1 or 2 storm.  Naturally, larger and more widespread evacuations take more time.  That underscores the need to have hurricane preparation plans in effect at the start of each hurricane season in June.

According to weather records that date back to 1851, a total of four Category 4 hurricanes have made landfall in the United States during the month of October, with the most recent being Hurricane Hazel in 1954.  Hazel had previously been the strongest October hurricane to make landfall with sustained winds of 130 mph a minimum central air pressure of 938 millibars.  However, Michael was much stronger than Hazel at peak intensity that was reached shortly before making landfall yesterday. 

Some may recall that Hurricane Irma was a Category 4 when it made landfall in southwest Florida in September 2017.  But, Hurricane Michael was more intense with higher sustained winds and a lower air pressure.  Sometimes, there is a lag time between a very low air pressure and a commensurate increase or decrease in the sustained wind speeds of a hurricane.

Overall, Hurricane Michael’s track was well-forecast as it was expected to track northward into the eastern Gulf of Mexico.  However, given Michael’s rare intensity at landfall it will take weeks if not months to measure its impacts both on the Gulf Coast and the southeastern United States.  It’s all but certain that for a third straight year the Atlantic Ocean will have an “M” storm retired.  Hurricanes “Matthew” in 2016 and “Maria” last year both saw their names subsequently retired.

Strongest Landfalling Hurricanes in Continental United States by Air Pressure (millibars or "mb")

Source: National Hurricane Center

1.  Florida Keys Labor Day Hurricane (1935) – 892 mb
2.  Camille (1969) – 900 mb
3.  Michael (2018) – 919 mb
4.  Katrina (2005) – 920 mb
5.  Andrew (1992) – 922 mb

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Strongest Landfalling Hurricanes in Continental United States by Sustained Wind Speeds (mph)

1.  Florida Keys Labor Day Hurricane (1935) – 185 mph
2.  Camille (1969) – 175 mph
3.  Andrew (1992) – 165 mph
4.  Michael (2018) – 155 mph
5.  Charley (2004) – 150 mph

--> Hurricane Charley was the most recent of five hurricanes to make landfall in the U.S. with 150 mph sustained winds

Michael and other Significant October Hurricanes

Hurricane Nate nearing landfall in October 2017  (Source: NOAA)

Michael was upgraded to hurricane status late this morning as it entered the southern Gulf of Mexico.  The National Hurricane Center currently expects Michael to be a major Category 3 hurricane when it approaches the Florida panhandle on Wednesday.  Let’s look at some other hurricanes that have impacted the United States in October. 

2017:  Hurricane Nate, made two landfalls in the United States in southeast Louisiana and near Biloxi, Mississippi on October 7-8 as a Category 1 hurricane.  According to the National Weather Service, Hurricane Nate at one point was moving 28 mph which set a record for fastest moving hurricane in the Gulf of Mexico.  It was also one of 10 consecutive hurricanes that developed last year in the Atlantic Ocean for the first time since 1893. 

2016: Hurricane Matthew was the first Category 5 hurricane to develop in the Atlantic Ocean since 2007.  That’s the second longest streak between Category 5 hurricanes on record in the Atlantic, behind the 15 years between the 1938 “New England” hurricane and Hurricane Carol in 1953.  At peak intensity with 165 mph sustained winds on October 1, Matthew weakened before it impacted Florida and the southeast coast of the United States.  The Carolinas saw record flooding that was eclipsed last month by Hurricane Florence.  

2002: Hurricane Lili reached peak intensity on October 2 while over the open Gulf of Mexico as a Category 4 storm with sustained winds of 145 mph.  Fortunately, Lili weakened precipitously before its landfall in Louisiana as a Category 1 hurricane.  It was the first hurricane to make landfall in the United States since Floyd in 1999.

1995:  At peak intensity on October 4, Opal was a powerful Category 4 storm with sustained winds of 150 mph and a minimum central air pressure of 916 millibars (mb).  The lower the air pressure, the stronger the storm is.  Standard sea level air pressure is approximately 1013.25 (mb).  Hurricane Opal broke the existing record set by Hurricane Gloria in 1985 (919 mb) for lowest air pressure in an Atlantic hurricane that did not reach Category 5 intensity.  By comparison, the lowest air pressure in Category 5 Hurricane Matthew was 934 mb two years ago. 

Although Opal weakened before landfall, it was still a major, Category 3 hurricane when it came ashore near Pensacola Beach, FL on October 4.  It had significant, far-reaching impacts both on the coast and inland.  The remnants of Hurricane Opal brought 1.99” of rain to the Nation’s Capital on October 5 and spawned three tornadoes in the Maryland (one each in Charles, Prince George’s and Anne Arundel Counties). 

DC’s Warm Start to October

Seven of the first nine months of 2018 were warmer than average in the Nation’s Capital.  The combination of this trend with NOAA’s forecast for above average October temperatures means this week’s warmer than average weather shouldn’t come as a surprise to anyone in the DC Metro Area.

Despite only one 90° day this month, October 2018 has gotten off to an exceptionally warm start.  Not since October 2013 have Washingtonians experienced at least four days with high temperatures of at least 81° to start the month.  Five of the last six Octobers have been warmer than average in the Nation’s Capital.  

Given the rainy second half of September with rain on eight of the final 10 days of the month, this warm and dry start to October has been welcomed by many DC area residents.  In fact, yesterday’s high temperature of 90° at National Airport was DC’s first 90° day since September 7 (91°).  Having 90° heat in October is rare in the Nation’s Capital, occurring roughly once every four to five years since 1993.  DC’s warmest October temperature on record is 96° (October 5, 1941) while the latest date in the year it has been 90° is October 11.  

By October, the length of daylight and sun angle are both significantly lower than during the summer.  Only one heat wave (3 or more consecutive 90° days) has occurred in the Nation’s Capital during the month of October in the last 25 years (October 7 – 9, 2007).  Average high temperatures in the Nation’s Capital fall significantly during the month of October from 74° to 64° by Halloween.

Area residents may recall that October can feature some very rainy and chilly conditions.  Record low high temperatures in the 40s occurred on October 16-17, 2009, while an early season Nor’Easter brought 1.2” of rain to DC on October 17, 2009.  More recently, a record low-high temperature of 42° occurred on October 29, 2011 with a trace of snow (not enough to measure).  A record “low-high” temperature means the 42° was much colder than the average high for the date of 64°.

Despite NOAA’s forecast for above average temperatures through mid-October across much of the eastern United States, the DC Area could see some cooler than average temperatures.  However, the overall weather pattern favors warmer and drier than average conditions for the DC Metro Area over the next few weeks.  By the end of the month, it is probable that October will become DC’s eighth warmer than average month of 2018.

Typical October Weather in DC ?

NOAA Expects Above Average October Temperatures Over the Eastern U.S.

September 2018 was a unique weather month in the Nation’s Capital. A total of 9.73” of rain was officially measured at National Airport, making last month the fifth wettest on record in Washington, D.C.  It also featured a record 16 days of measurable rainfall.

Also, September 2018 finished tied with September 2010 for DC’s fifth warmest on record with a monthly average temperature (combining daily high and low temperatures) of 75.5°.  That’s the first time DC has had a September that ranked in the Top Five wettest and warmest months since official weather records began in 1871.  Despite measurable rainfall on eight of the final 10 days of September, temperatures were above average on seven of those 10 days.

October 2018 has gotten off to a much drier start.  Warmer than average temperatures are expected to continue for the first half of the month.  In fact, NOAA’s outlook for the entire month of October is for warmer than average temperatures with near average precipitation.  Near average precipitation should sound good to the majority of Washingtonians, following the especially rainy weather over the final third of September.

DC’s average high/low temperatures drop significantly over the course of the month from 74°/56° on the October 1 to 64°/46° on October 31.  DC’s hottest October temperature on record was 96° on October 5, 1941.  Meanwhile, DC’s coldest observed October temperature of 26° has occurred three times, most recently on October 31, 1917.  Eleven of the last 20 October’s, have been warmer than average in Washington, D.C., including five of the last six.

Although rare, the Nation’s Capital can experience 90° heat in early October.  The last time 90°/+ heat was observed in Washington, D.C. was on October 6, 2013 (91°).  Temperatures at or below freezing in October are also relatively rare in the Nation’s Capital, with the majority of such temperatures occurring before National Airport opened in the early 1940s.  Prior to National Airport opening, weather records for the Nation’s Capital were kept downtown.  Overall, the last time temperatures at or below freezing occurred in the Nation’s Capital during the month of October was on October 20, 1992 (32°).

Washington, D.C. averages 3.4” of rain in October and half of the last 20 October’s have been wetter than average.  The DC Metro Area occasionally experiences heavy rain from former tropical systems such as the remnants of Hurricane Opal that produced 1.99” of rain on October 5, 1995 and ex-Hurricane Sandy that produced 4.69” of rain on October 29-30, 2012.  The earliest in the season the Nation’s Capital has had measurable snowfall was October 10, 1979 (0.3”).

NOAA's Precipitation Outlook for October