Season summary 2010 Atlantic hurricane season

unlike 2010 pacific hurricane season, tied 1977 least active year in reliable records, 2010 atlantic hurricane season ended 1 of active in recorded history. began on june 1 , ended on november 30, dates conventionally delimit period during each year when tropical cyclones form in atlantic ocean. first system of season, hurricane alex, developed on june 25; final system of season, hurricane tomas, dissipated on november 7. total of 21 tropical depressions formed within basin, of 19 intensified tropical storms, 12 intensified hurricanes, , 5 further intensified major hurricanes. season s 19 tropical storms tied previous years 1887 , 1995, subsequent years 2011 , 2012, third highest count on record; 2005 , 1933 featured more activity. year s 12 hurricanes matched 1969 second highest count on record, exceeded 2005. there more tropical storms in atlantic west pacific in 2010, second such occurrence on record after 2005. throughout entire atlantic tropical cyclone database, 2010 year more 10 hurricanes not feature hurricane landfall on united states.

satellite image of 3 simultaneous tropical cyclones on september 16. left right: karl, igor , julia

several factors contributed exceptional activity. strong el niño observed in 2009 rapidly transitioned strong la niña mid-summer 2010, projecting anomalously low vertical wind shear across atlantic ocean. ocean temperatures reached record levels across basin, averaging @ 0.82 °c above 1981–2010 average. not did ocean temperatures surpass 2005 break record overall, averaged water temperatures across main development region (mdr) of atlantic set monthly records february october 2010. aided negative north atlantic oscillation contributed weaker trade winds , anomalous warming of ocean temperatures in months leading hurricane season. lower sea level pressures prevalent throughout of season, trailing 1955 lowest average values across mdr during august october period. in spite of high number of tropical cyclones, mid-level dry air dominated tropical atlantic throughout peak of season, perhaps hindering season being more active.

the beginning of atlantic season featured alex, first hurricane observed in june since 1995 s hurricane allison. 1 tropical storm, bonnie, , tropical depression formed in month of july. august featured 5 cyclones – tropical depression, tropical storms colin , fiona, hurricanes danielle , earl (both of further intensified major hurricanes). in accordance climatological norms, september active month of season, featuring 8 tropical cyclones: tropical storms gaston, hermine, matthew, , nicole, hurricanes igor, julia, karl, , lisa. tied 2002 tropical storms observed throughout month. igor attained peak winds of 155 mph (250 km/h) on september 15, cementing status intense storm of season. above-average activity continued october, formation of hurricanes otto, paula, richard, shary, , tomas, 1 hurricane short of monthly record set in 1870. tomas persisted subsequent month before dissipating on november 7, heralding end of season s tropical cyclone activity.

the season s activity reflected ace rating of approximately 165 units, highest since 2005, , eleventh highest value since 1944 @ time. broadly speaking, ace measure of power of tropical or subtropical storm multiplied length of time existed. therefore, storm longer duration, such igor, have high values of ace. calculated full advisories on specific tropical , subtropical systems reaching or exceeding wind speeds of 39 mph (63 km/h). accordingly, tropical depressions not included in count. after storm has dissipated, typically after end of season, nhc re-examines data , produces final report on each storm. these revisions can lead revised ace total either upward or downward compared original value.