Can hurricanes be upgraded or downgraded?

 

Hurricane Michael, October 2018 (Source: NOAA)

NOAA scientists study hurricanes for months and sometimes years after the final advisory has been written on them. Tropical storms and hurricanes can provide lessons on forecasting and emergency preparedness. Occasionally, a hurricane’s intensity is updated after the fact to reflect the research done by NOAA. 

2020: The 2020 season was one for the record books with 30 tropical storms in the Atlantic. Hurricane Iota was originally classified as only the second November Category 5 storm on record with peak sustained winds of 160 mph. However, meteorologists took a closer look at the accumulated data that winter and determined it was an upper echelon Category 4 storm at peak intensity, with its highest sustained winds of 155 mph (just below Category 5 status). That made 2020 the first season since 2015 that no Category 5 Atlantic hurricanes occurred.

2019: In the spring of 2019, NOAA determined Hurricane Michael was indeed a Category 5 hurricane at its time of landfall on the U.S. Gulf Coast in October 2018. Originally, it was thought to be an upper end Category 4 hurricane, just below Category 5 status with sustained winds of 155 mph. However, according to NOAA’s post-analysis Michael had sustained winds of 160 mph. While there is little tangible difference between these wind speeds in terms of damage, reclassifying Michael as Category 5 changed a host of historical records.

The upgraded Michael became only the fourth Category 5 hurricane to ever make landfall in the United States and the first since Andrew in 1992. The two other Category 5 hurricanes to make landfall are Camille (1969) and the unnamed Florida Keys 1935 hurricane. Overall, Category 5 hurricanes are exceedingly rare since they require ideal environmental conditions to develop.

2002: On the 10^th anniversary of Hurricane Andrew, NOAA determined it was actually a Category 5 hurricane when it made landfall in south Florida. Originally, it was ranked as a Category 4 hurricane with sustained winds of 145 mph during its Florida landfall on August 24, 1992. Years of post-analysis study led scientists to reclassify Hurricane Andrew as a Category 5 with sustained winds of 165 mph.

Andrew had the infamous distinction for more than a decade of being the costliest natural disaster in U.S. history. Although more recent hurricanes like Katrina, Harvey and Irma have each caused more damage than Andrew, it still ranks among the Top 10 costliest U.S. hurricanes.

Little did people realize it at the time, but Andrew occurred three short years before a more active cycle began in the tropical Atlantic. From the 1970s through the early 1990s, the tropical Atlantic was relatively quiet with below average tropical activity. However, there has been a series of active Atlantic seasons since 1995. That’s why listening to the latest forecasts from NOAA’s National Hurricane Center and your favorite local meteorologists is of critical importance.

Summertime in April?

 

An April day in Montgomery County, Maryland

A “heat wave” is loosely defined as a minimum of three consecutive days of 90-degree heat. Since the nation’s capital doesn’t typically see its first 90-degree day of the year until on or around May 18, any 90-degree April heat is unusual.  So, having three days of it isn’t necessary to make it feel like a “heat wave” this early in the season.

2026: The nation’s capital has averaged roughly one 90-degree April day every three to four years over the last 30 years, according to NOAA. Prior to this month, there hadn’t been any 90-degree April heat since 2017. That’s what made the highs of 90° this past April 15 and 16 stand out among Washingtonians. On top of that, 14 of the first 18 days of the month were warmer than average. That development contributed to this month being more than 8° warmer than average through April 18.

2017: This April finished as the warmest on record in the nation’s capital having finished more than 5.5° warmer than average. There were nine days that featured highs in the 80s, roughly double the 30-year average of between three and four such days. To add to that, there was a record-tying high of 91° on April 29, 2017.

2010: Before this month, April 2010 was the last time two days saw 90-degree heat at National Airport. Highs of 90° occurred in the nation’s capital on April 6 and 7.  That helped make April 2010 DC’s warmest since 1994.

2002: The last time the nation’s capital experienced what would meet the summertime criteria of a “heat wave” was 24 years ago.  That’s when Washingtonians sweated through three consecutive days of 90-degree heat from April 16-18. DC’s high temperature of 95° on April 17, 2002, not only set a record high for the date, but that also tied the record high for the entire month of April.

1994: This April remains the fifth warmest on record in the nation’s capital. While it had only one day of 90-degree heat, there were seven days high temperatures were in the 80s.

Warmest April’s in Washington, D.C. (Source: NOAA)

1. 63.8° (2017)
2. 62.4° (2019)
3. 62.1° (2023, 1981)
5. 62.0° (1994)
6. 61.7° (2025)
7. 61.6° (1985)
8. 61.2° (1960)
9. 60.9° (2010)
10. 60.6° (1941)
11. 60.5° (2024)

Beware tornadoes in the DMV

 

July 1, 2021 severe weather reports (Source: NOAA)

The Mid-Atlantic Region sees most of its severe weather in May and June, with a secondary peak in the fall as the seasons begin to change. The remnants of tropical systems can also spawn tornadoes when they impact the Mid-Atlantic Region, such as with Hurricane Isaias in 2020. 

Tornadoes associated with decaying tropical systems are typically weaker than those that develop within supercell thunderstorms. Tornadic thunderstorms are exceedingly rare within DC city limits, with only five since 1950. The most recent occurrence was on July 1, 2021, when an EF-0 and an EF-1 occurred.   

Two more EF-0 tornadoes occurred in the nation’s capital on April 6, 2017. They caused only minor damage and, fortunately, no fatalities. These tornadoes occurred as part of a larger, three-day severe weather outbreak. From April 4 through April 6, 2017, there were 550 reported cases of severe weather from the Midwest to the East Coast, which included 30 tornadoes. These were the first tornadoes in the nation’s capital since September 24, 2001. DC’s strongest tornado on record was an F3 that developed in Rock Creek Park on April 5, 1923.

Maryland has had three significant tornadoes in the last 30 years. An exceptionally rare F4 tornado developed in Charles County on April 28, 2002. This tornado had a track that spanned nearly 70 miles. It reached its peak intensity as it passed through the town of La Plata with winds of nearly 260 mph. It caused more than $100 million in damage (unadjusted for inflation), in addition to five fatalities and dozens of injuries, according to NOAA. The 2002 La Plata tornado remains the strongest tornado on record in Maryland.

The town of College Park, Maryland saw a F3 tornado on September 24, 2001. Tragically, two sisters, who were students at the University of Maryland, lost their lives during this tornado, which also caused extensive damage. In addition, an F4 tornado occurred on June 2, 1998 in Frostburg, Maryland. Wind speeds of the Frostburg tornado were estimated to be as high as 210 mph.

According to NOAA data, Maryland averages between six and 10 tornadoes annually, while Virginia sees close to 20. The two strongest tornadoes on record in Virginia were F4s. One occurred on August 6, 1993, and the second on September 24, 2001.  

Tornado intensity is measured on the Fujita Scale that was named after the late Dr. Ted Fujita of the University of Chicago who designed it in 1971. It has since been updated and became the “Enhanced Fujita” or EF scale in 2007.