This coming Friday (30 November 2018) signals the end of the
official 2018 hurricane season in the North Atlantic basin (which
includes the Gulf of Mexico and the Caribbean), the Eastern North
Pacific basin (a region extending from the western coast line of North
America westward to a longitude of 140 degrees west) and the Central North Pacific basin (westward from the 140th meridian to the International Dateline). While a named tropical cyclone (hurricane
or tropical storm) may develop in these basins after 30 November, such an event
is rare. Considering the period of record in the North Atlantic that extends back to 1851, the latest recorded hurricane was the second Hurricane Alice of the year on 31
December 1954, while on 31 December 2005 Tropical Storm Zeta formed and continued into the new year. The earliest recorded Atlantic hurricane
for any season was Hurricane
Alex, which formed on 14 January 2016.
In the eastern North Pacific basin,
the latest hurricane of the season of record (since 1949) was Hurricane Winnie,
which became a category-1 hurricane (on the
Saffir-Simpson Scale) on 6 December 1983 and dissipated a
day later, while the earliest hurricane of the season for that basin
was Hurricane Alma, a category-1 hurricane that formed on 12 May 1990 and reached hurricane
status on the 15th.
In the central North Pacific basin, the latest hurricane to have formed in a season during modern times (since 1957) was Hurricane Iwa, which reached hurricane strength on 23 November 1983. On the other hand, the earliest hurricane to form in the central Pacific was Hurricane Pali that formed on 11 January 2016.
With 16 named tropical (and subtropical) cyclones having formed in the Atlantic basin as of late November 2018, this current year ranks as the tenth most active season since 1851, tied with 1936, 2003, and 2008. Eight of these named tropical cyclones developed into hurricanes (with
maximum sustained winds in excess of 74 mph). Two of these hurricanes (Florence and Michael) became major
hurricanes (category-3 or higher on the Saffir-Simpson Hurricane
Intensity Scale), with both reaching category 4 status. One tropical depression formed. (A subtropical cyclone is a hybrid system, having both tropical and extratropical characteristics.)
The first named tropical system of the 2018 Atlantic season was Subtropical Storm Alberto that formed on 25 April over the northwestern Caribbean Sea offshore of Yucatan Peninsula. As of this writing, the last tropical cyclone of this season was Hurricane Oscar, a category 2 hurricane that lost its tropical characteristics on 31 October as it was heading to the north-northeast approximately 540 miles to the southeast of Newfoundland.
Two hurricanes (Florence and Michael) made landfall along the Atlantic or Gulf coasts of the mainland United States in 2018. Hurricane Florence, which had reached category 4 status earlier, made landfall along the North Carolina coast as a category 1 hurricane on 14 September before taking a slow track toward the southwest and then northward, spreading torrential rains across the Carolinas and Virginia. Hurricane Michael became a high-end category-4 hurricane over the Gulf of Mexico before making landfall along the Florida Peninsula between Panama City and Mexico Beach on 10 October. Catastrophic damage resulted across the Florida Panhandle. Subtropical Storm Alberto and Tropical Storm Gordon also made landfall along the U.S. coast.
Additional information concerning several of the individual tropical cyclones
during this season will be forthcoming at https://www.nhc.noaa.gov/data/tcr/index.php?season=2018&basin=atl with a preliminary map showing the tracks of these systems across the basin. More details should appear in the next few weeks, as the final version of the North Atlantic summary is prepared.
In the eastern North Pacific, the hurricane season runs from 15 May to 30 November. As of the last week of November, the 2018 hurricane season had 21 named
tropical cyclones, with 11 reaching hurricane status. Three tropical depressions were reported. Nine hurricanes became major
(category-3 or greater) hurricanes, with seven becoming category-4 hurricanes and two reaching category-5 status (Hurricanes Lane and Willa).
The first named tropical cyclone in the eastern Pacific during 2018 was Tropical Storm Aletta, which became a tropical storm on 7 June and then a category 4 hurricane at least 400 miles to the west-southwest of Manzanillo, Mexico. The last tropical cyclone of the year (as of the time of this writing) was Tropical Storm Xavier, which formed slightly more than 200 miles south of El Salvador before making landfall along the coast of El Salvador on 6 November.
While most of the tropical systems remained well off the coasts of Mexico and
Central America, three hurricanes (Bud, Sergio and Willa) and one tropical storm (Vicente) made landfall along the western coast of Mexico. Several of the long-lived tropical cyclones traveled westward and exited into the central Pacific basin (see below). Hurricane Olivia, a former category 4 hurricane while in the eastern Pacific, crossed the central Pacific basin and eventually made landfall on Maui and Lanai in the central Hawaiian Islands as a tropical storm.
For additional information concerning some
of these tropical cyclones including a preliminary map of their tracks across the basin, see https://www.nhc.noaa.gov/data/tcr/index.php?season=2018&basin=epac.
More details should be forthcoming in the Eastern North Pacific
summary.
The region of the North Pacific Ocean lying between 140
degrees west and the International Dateline (180 degrees longitude) is
identified as the Central North Pacific Basin. The hurricane season for
this basin officially begins on 1 June and ends on 30 November. The
region is monitored by the National Weather Service Forecast Office in
Honolulu, which activates the Central Pacific Hurricane Center (CPHC)
when tropical cyclone activity becomes imminent in this basin.
During the 2018 season, five hurricanes entered the central Pacific basin from the eastern Pacific basin in August and September. In addition, Hurricane Walaka formed within the basin and intensified to become a category 5 hurricane as it passed to the southwest and west of the western Hawaiian Islands. Three of the hurricanes coming from the eastern Pacific were major hurricanes or became major hurricanes that continued to travel long distances across the central Pacific, passing the Hawaiian Islands. Hector was a category 4 that passed to the south of Hawaii's Big Island. Lane became a category 5 hurricane before passing to the south of the Hawaiian Islands. Norman passed to the northeast of the Hawaiian Islands as a category 3 hurricane. Olivia, which had become a category 4 hurricane in the eastern Pacific basin, crossed the central Hawaiian Islands as a tropical storm. For
additional information concerning tropical cyclones in the Central North Pacific, see http://www.prh.noaa.gov/cphc/tcpages/archive.php.
The fifteen named tropical cyclones that formed during the 2018 North Atlantic hurricane season meant that the season was more active than average, as a typical North Atlantic hurricane season would have slightly more than ten named systems, based upon long-term averages running from 1931 to 2010. Furthermore, the eight hurricanes in 2018 were more than the average number of six per annum for the last 80 years, as were the seven tropical storms that were more than the long-term annual average of nearly five tropical storms. However, the two major hurricanes in 2018 were less than the long-term average of three hurricanes that reach at least category-3 status. For comparison, the record active 2005 season had 28 named systems, with 13 classified as hurricanes and eight tropical storms; seven of the hurricanes during that year became major hurricanes. Conversely, the least active season in recent history was 1983 when only four named tropical cyclones were reported (three hurricanes and one tropical storm). Only two hurricanes formed in 1982 and 2013, which represent the two years with the fewest hurricanes since 1931. Interestingly, a record number of subtropical storms formed in 2018, with six eventually becoming tropical storms or hurricanes; only Subtropical Storm Alberto did not make a transition.
The late Professor William Gray and Philip Klotzbach, hurricane experts from Colorado State University in Fort Collins, have been issuing
long-range Atlantic hurricane forecasts for more than two decades. Their forecasts are based upon several factors that include analysis of the
wind field at several levels, the rainfall over West Africa and the effects of El Niño. For additional information on these forecasts, refer to http://tropical.atmos.colostate.edu/forecasts/. In early April 2018, Klotzbach's team released its initial forecast of the 2018 North Atlantic hurricane season that indicated a slightly above-average season in terms of the number of tropical cyclones. In this initial forecast, fourteen named tropical cyclones were envisioned, which included seven hurricanes. Of these hurricanes, the forecasters foresaw three major hurricanes. A slightly above-average probability was anticipated for major hurricanes making landfall along the United States coastline and in the Caribbean in 2018. The team had based their initial outlook upon the transition of the weak La Niña to ENSO-neutral conditions occurring over the summer. However, subsequent outlooks prepared in June and July began to favor an average then slightly-below average hurricane season because of cooler than average sea surface temperatures across the eastern North Atlantic and an increased chance of weak El Niño conditions developing during the hurricane season. Klotzbach issued a final updated forecast in August that called for a total of twelve named tropical cyclones for the entire 2018 season, with five potentially becoming hurricanes. One major hurricane was also envisioned.
Forecasters with NOAA's Climate Prediction Center (CPC) also generated an outlook for the 2018 Atlantic hurricane season in mid-May. They foresaw a hurricane season with an average to above-average activity, giving a 70-percent chance that the basin could experience 10 to 16 named tropical cyclones. The forecasters also felt that five to nine tropical cyclones could become hurricanes, with as many as four of these hurricanes possibly becoming major hurricanes. The forecasters anticipated weak El Niño conditions developing during the hurricane season, near- or above-average sea-surface temperatures across the tropical Atlantic Ocean and Caribbean Sea, and the continuation of the high-activity era for Atlantic hurricane seasons since the mid-1990s.
The 2018 season in the eastern North Pacific with 22 named systems tied 1985 for the second most active season on record, and is more than the long-term (1966-2012) average of slightly more than 15 named tropical cyclones. The twelve hurricanes in 2018 was also above the long-term average of slightly more than eight hurricanes per annum. The ten major hurricanes in 2018 was more than twice the long-term average of slightly more than four in a year. Furthermore, the six landfalling system in 2018 tied 1971 for the highest number of tropical cyclone landfalls in a single season. In May 2018 CPC forecasters had issued an outlook for the eastern North Pacific basin that called for a near- to above-normal hurricane season with a 70-percent chance of the formation of between 14 and 20 named tropical cyclones, with seven to twelve hurricanes. Between three and seven major hurricanes were also envisioned. This outlook was based upon the expectation of ENSO-neutral or weak El Niño conditions, along with above-average sea-surface temperatures across the eastern and central tropical North Pacific.
The 2018 season in Central North Pacific basin was very active as compared to the long-term average as six named tropical cyclones traversed sections of the basin. Over the last 60 years, slightly more than three named tropical cyclones either developed or entered this basin from the east on average and an average of one hurricane that typically forms only once in two years. CPC forecasters in May 2018
had issued an outlook for the central North Pacific basin with activity ranging from near- to above-average. Three to six tropical cyclones were expected to
affect the central North Pacific in 2018, either forming within the
basin or entering it from the Eastern Pacific. At the time, the forecasters had anticipated a transition from ENSO-neutral to a weak El Niño during the hurricane season, along with near- or above-average ocean temperatures in the main hurricane formation region, along with near- or weaker-than-average vertical wind shear.
The National Hurricane Center (NHC) has an updated and revised
edition of its "Tropical Cyclones of the North Atlantic Ocean,
1851-2006." While a paper copy of this book is available for a cost
from NHC, a 243-pg pdf file of this edition can be downloaded for free.
NHC also released the first edition of
"Tropical Cyclones of the Eastern North Pacific Ocean, 1949-2006." In
addition to a paper copy that is available for sale, a free 164-page pdf
file is available online.
Both of these climatologies have numerous graphics that show long-term
changes in tropical cyclone frequency in the two basins.
A climatology of tropical cyclones in the central North Pacific from
the 1950s to 2013 is available from the CPHC
climatology website maintained by the Central Pacific
Hurricane Center (CPHC) in Honolulu, HI. A compilation of individual tropical cyclones in the central Pacific is also available by year extending back to 1957, along with notable systems dating back into the 19th century.
