View source for Hurricane Ava

{{Short description|Category 5 Pacific hurricane in 1973}}
{{Other hurricane uses|List of storms named Ava|the 1973 Pacific hurricane}}
{{Infobox weather event
| image = Hurricane Ava (1973).PNG
| caption = Ava near peak intensity on June 6
| formed = June 2, 1973
| dissipated = June 12, 1973
}}{{Infobox weather event/NWS
| winds = 140
| pressure = 915
}}{{Infobox weather event/Effects
| year = 1973
| fatalities = None
| damage = None
| areas = [[California]]
}}{{Infobox weather event/Footer
| season = [[1973 Pacific hurricane season]]
}}
'''Hurricane Ava''' was the earliest forming Category 5 hurricane on record in the East Pacific basin. The storm is also tied with 2006's [[Hurricane Ioke]] as the fifth-strongest [[Pacific hurricane]] on record. It was the first named storm of the [[1973 Pacific hurricane season]]. Forming in early June, Hurricane Ava eventually reached Category&nbsp;5 intensity on the [[Saffir–Simpson hurricane scale]], the first [[Pacific hurricane]] to do so in June and the earliest ever in a [[Pacific hurricane season|season]]. Its [[atmospheric pressure|central pressure]] made it the most intense known Pacific hurricane at the time. Despite its intensity, Ava stayed at sea without significant impact.

Ava was given the most advanced measurement and reconnaissance available at the time. Recon flights were conducted and meteorological equipment was tested. The hurricane was also photographed from space by satellites and [[Skylab]] astronauts.

==Meteorological history==
{{storm path|Ava 1973 track.png}}
On June 2, 1973, a tropical depression formed about {{convert|250|mi|km}} south of [[Salina Cruz, Oaxaca]]. It started out nearly stationary, and became a tropical storm late on the same day it formed, the first named storm of the [[1973 Pacific hurricane season]]. Ava then slowly moved westwards away from Mexico and became a hurricane on June 3. Ava became a major hurricane on the afternoon of June 5. On the next day, a United States Air Force recon flight measured a wind speed of {{convert|150|mph|kph|abbr=off|sp=us}} and a [[atmospheric pressure|central pressure]] of {{convert|915|mbar|inHg|abbr=off}}. These measurements made Hurricane Ava by far the most intense storm of the season.<ref name="mwr">{{cite journal|date=April 1974|title=Eastern North Pacific Hurricane Season of 1973|author=Robert A. Baum|publisher=[[American Meteorological Society]]|journal=[[Monthly Weather Review]]|volume=102|issue=4|pages=297–301|doi=10.1175/1520-0493(1974)102<0296:ENPHSO>2.0.CO;2|bibcode=1974MWRv..102..296B|doi-access=free}}</ref>

At its peak, Ava had winds of {{convert|160|mph|kph|abbr=on}}.<ref name="mwr"/> These winds made the storm a Category&nbsp;5 hurricane on the [[Saffir–Simpson hurricane scale]] (SSHS), the highest category on the scale,<ref name=SSHS>{{cite web|title=Saffir–Simpson Hurricane Scale|publisher=[[National Hurricane Center]]|url=http://www.nhc.noaa.gov/aboutsshs.shtml|access-date=2008-01-04}}</ref> and the first Category&nbsp;5 hurricane since the [[1959 Pacific hurricane season|1959 season]].{{EPAC hurricane best track}} Ava was also a hurricane with windspeeds rapidly increasing the closer to the [[eye (cyclone)|eye]] they were measured. Over a distance of {{convert|4|mi|abbr=on}}, wind speeds increased from {{convert|70|to|158|mph|kph|abbr=on}}, and they increased from {{convert|105|to|158|mph|kph|abbr=on}} over half that distance. The reading of {{convert|915|mbar|inHg|abbr=on}} was roughly {{convert|100|mbar|inHg|abbr=on}} lower than the ambient environment far from the storm.<ref name="mwr"/>

After its peak, Ava started weakening on June 7, as it continued its westward path. Its winds were {{convert|140|mph|kph|abbr=on|round=5}} on June 7 and {{convert|115|mph|kph|abbr=on}} on the next day. It was no longer a major hurricane after its winds fell to {{convert|105|mph|kph|abbr=on}} on June 9. Later that day it weakened to a tropical storm. It then weakened to a tropical depression on June 11. The system then turned north and dissipated on June 12. Its remnants then became embedded in the [[trade winds]] as a [[tropical wave]].<ref name="mwr"/>

==Forecasting and observation==
[[File:C130 tail radar in Hurricane Ava.jpg|200px|right|thumb|Radar during a recon flight]]

In terms of how well it was [[tropical cyclone forecasting|forecast]], Ava had the largest error of any cyclone during the season. This 14° error five days out was mainly due to its northward turn when it was a weakening depression.<ref name="mwr"/>

For a few days, Ava was directly underneath [[Skylab]] during [[Skylab 2|its first crewed mission]].<ref name="mwr"/> Astronauts acquired photographs of the hurricane,<ref name=Ch1>{{cite web|url=https://history.nasa.gov/SP-399/ch1.htm|title=Introduction|work=SP-399 Skylab EREP Investigations Summary|publisher=[[National Aeronautics and Space Administration]]|access-date=2008-01-04}}</ref> which was big enough for Science Pilot [[Joseph P. Kerwin|Joseph Kerwin]] to describe it as "an enormous spiral" that was big enough to dominate the view outside the space station's window and prevent anything else from being seen.<ref name=UPI>{{cite news|publisher=The Hurricane Newspaper Archive|date=1973-06-08|page=13|work=The Daily Courier|place=Connellsville, Pennsylvania|title=First Hurricane}}</ref> Astronauts also provided microwave data through Earth Resources Experiment Package sensors.<ref name=Ch1/> Skylab also used a [[scatterometer]] on the system.<ref name=DTIC>{{cite web|url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA010517|author=Arthur K. Jordan, Charles G, Purves, & James F. Diggs|title=Analysis of Skylab II S193 Scatterometer Data|publisher=[[Defense Technical Information Center]]|date=1975-05-02|access-date=2008-01-04|archive-url=https://web.archive.org/web/20140103213108/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA010517|archive-date=2014-01-03|url-status=dead}}</ref> Unfortunately, Skylab's scatterometer data was harder to use than normal as it was [[degradation (telecommunications)|degraded]].<ref name="Kaupp and Holtzman">{{cite journal|title=Skylab Scatterometer Measurements of Hurricane Ava: Anomalous Data Correction|publisher=IEEE|journal=IEEE Transactions on Geoscience Electronics|date=January 1979|author1=V. H. Kaupp |author2=J. C. Holtzman |volume=17|issue=1|pages=6|doi=10.1109/TGE.1979.294602|bibcode=1979ITGE...17....6K|s2cid=40700911|doi-access=free}}</ref>

Ava was also underneath the NOAA-2 and [[Nimbus program|Nimbus 5]] [[weather satellite]]s. NOAA-2 provided photographs that were used to estimate Ava's maximum windspeeds. Satellite images were useful throughout the cyclone's existence, as did the wind reports of three ships when Ava was a young tropical storm.<ref name="mwr"/> [[Nimbus program|Nimbus 5]] carried an Electrically Scanning Microwave [[Radiometer]] and Temperature-Humidity Infrared Radiometer.<ref name="ARWW p 1074">{{cite journal|author1=Lewis J. Allison |author2=Edward B. Rodgers |author3=Thomas B. Wilheit |author4=Robert W. Fett |title=Tropical Cyclone Rainfall as Measured by the Nimbus 5 Electrically Scanning Microwave Radiometer|publisher=[[American Meteorological Society]]|date=September 1974|journal=[[Bulletin of the American Meteorological Society]]|volume=55|issue=9|pages=1074–1089|doi=10.1175/1520-0477(1974)055<1074:TCRAMB>2.0.CO;2|bibcode=1974BAMS...55.1074A |doi-access=free}}</ref> Both were used to study Ava. The main data provided by the THIR was data indicating cloud temperatures. The ESMR's main data was on rainfall rates, densities, and distributions. The observations also provided confirmation that clouds that are not vertically developed very much can produce tropical rainfall.<ref name="ARWW p 1077">{{cite journal|author1=Lewis J. Allison |author2=Edward B. Rodgers |author3=Thomas B. Wilheit |author4=Robert W. Fett |title=Tropical Cyclone Rainfall as Measured by the Nimbus 5 Electrically Scanning Microwave Radiometer|publisher=[[American Meteorological Society]]|date=September 1974|journal=[[Bulletin of the American Meteorological Society]]|volume=55|issue=9|pages=1077|doi=10.1175/1520-0477(1974)055<1074:TCRAMB>2.0.CO;2|bibcode=1974BAMS...55.1074A |doi-access=free}}</ref>

Recon aircraft also penetrated Hurricane Ava. It was the first [[Pacific hurricane]] penetrated by [[National Oceanographic and Atmospheric Administration]] aircraft,<ref name=radarpic>{{cite web|url=http://www.photolib.noaa.gov/htmls/wea01151.htm|title=Wea01151|publisher=[[National Oceanographic and Atmospheric Administration]]|work=NOAA Photo Library|access-date=2008-01-05}}</ref> but not by aircraft from other agencies.<ref name="Padgett aug 2000">{{cite web|url=http://www.australiansevereweather.com.au/cyclones/2001/summ0008.htm|title=Monthly Global Tropical Cyclone Summary August 2000|author=Gary Padgett|access-date=2008-01-05}}</ref> NOAA craft were laden with sensors and measured wave heights reaching {{convert|40|ft|m|abbr=off}} with a microwave [[radar]] system and a laser [[altimeter]].<ref name="mwr"/> That was the first time ever that sea conditions in a tropical cyclone had been measured that way.<ref name="mwr"/> United States Air Force planes measured central pressure, air temperature, and humidity in the [[eye (cyclone)|eye]] pressures using [[dropsonde]]s.<ref name="mwr"/> The collection of data from both space and the air was done in order to allow comparisons.<ref name=Shayler>{{cite book|url=https://books.google.com/books?id=X4WaYqQDVKwC&q=%22hurricane+ava%22+skylab+comparative&pg=PA267|title=Skylab: America's Space Station|author=David Shayler|page=267|year=2001|publisher=Springer |isbn=978-1-85233-407-9|access-date=2008-01-04}}</ref> Collectively, all of this measuring made Hurricane Ava the best-measured northeastern Pacific [[tropical cyclone]] at the time.<ref name="mwr"/>

==Impact and records==
{{Most intense Pacific hurricanes|align=right}}
Hurricane Ava stayed at sea.<ref name="Unisys map">{{cite web|url=http://www.weather.unisys.com/hurricane/e_pacific/1973/AVA/track.gif|format=GIF|title=Hurricane AVA|publisher=Unisys|access-date=2008-01-04|archive-url=https://web.archive.org/web/20140103204241/http://www.weather.unisys.com/hurricane/e_pacific/1973/AVA/track.gif|archive-date=2014-01-03|url-status=dead}}</ref> Consequently, no one was killed and there was no reported damage. However, when it was a recently named tropical storm, Ava did cause sustained winds below [[gale]]-force to three ships called the ''Joseph Lykes'', ''Hoegh Trotter'', and ''Volnay''.<ref name="mwr"/> In addition, large ocean waves churned up by Ava created hazardous surf and strong riptides at Southern California beaches on June 9 and June 10. Those waves reached heights of up to {{convert|9|ft|abbr=on}} at [[Newport Beach, California|Newport Beach]], {{convert|6|ft|abbr=on}} at [[Long Beach, California|Long Beach]], and {{convert|8|ft|abbr=on}} at [[Seal Beach, California|Seal Beach]]. Those waves made beaches more hazardous, resulting in double-to-triple the usual contingent of [[lifeguard]]s throughout Southern California beaches. At Seal Beach and Newport Beach, lifeguards made 35 and 75 rescues, respectively.<ref name=Williams>{{cite news|publisher=The Hurricane Newspaper Archive|date=1973-06-11|work=Long Beach Independent|author=Tom Williams|page=A3|title='Hurricane surf' hits Southland; lifeguards busy|place=Long Beach, California}}</ref>

When it was active, Hurricane Ava set many records. Several have since been broken, but Ava still holds a few. Ava ceased being a Category&nbsp;5 hurricane on June 7, 1973.<ref name="EPAC HURDAT"/> [[Hurricane Emilia (1994)|Emilia (1994)]] reached Category&nbsp;5 intensity on July 19, 1994.<ref name="CPHC 1994">{{cite web|url=http://www.prh.noaa.gov/cphc/summaries/1994.php|title=The 1994 Central Pacific Tropical Cyclone Season|access-date=2008-01-06|publisher=[[Central Pacific Hurricane Center]]}}</ref> This span of 7,712&nbsp;days, which Ava began and Emilia ended, is the longest time between successive Category&nbsp;5 hurricanes in the northeastern Pacific, and anywhere worldwide, in recorded history. When Hurricane Gilma reached Category&nbsp;5 strength on July 24, also in 1994, it marked the shortest gap between Category&nbsp;5 Pacific hurricanes recorded.<ref name="EPAC HURDAT"/> Ava was also a Category&nbsp;5 hurricane for exactly 24&nbsp;hours; a record at the time. [[Hurricane John (1994)|Hurricane John]] broke that in the [[1994 Pacific hurricane season|1994 season]], and hurricanes [[Hurricane Linda (1997)|Linda]] and [[Hurricane Ioke|Ioke]] also lasted longer, tied with John.<ref name=E8>{{cite web|url=http://www.aoml.noaa.gov/hrd/tcfaq/E8.html|author=Neal Dorst|title=Subject: E8) What hurricanes have been at Category Five status the longest?|date=2004-08-13|work=FAQ|access-date=2008-01-06|publisher=[[National Hurricane Center]]}}</ref> In addition, Ava is the strongest June tropical cyclone in the western hemisphere north of the equator.<ref name="EPAC HURDAT"/>{{Atlantic hurricane best track}}

A spokesperson from the U.S. [[National Weather Service]] was quoted as saying that, "Ava had sustained winds of about 180&nbsp;knots with some gusts at 200&nbsp;knots when she {{sic}} was peaking".<ref name=Williams/> However, the official "Best track" data file and the seasonal summary in the ''[[Monthly Weather Review]]'' contradict that report and give maximum winds of 140&nbsp;knots.<ref name="mwr"/><ref name="EPAC HURDAT"/> If Ava's winds were that high, they would one of the highest ever reported in a tropical cyclone anywhere. Like any report of winds that high it is suspect.<ref name=E1>{{cite web|url=http://www.aoml.noaa.gov/hrd/tcfaq/E8.html|title=Subject: E1) Which is the most intense tropical cyclone on record?|author=Chris Landsea|work=FAQ|date=2006-11-28|publisher=[[National Hurricane Center]]|access-date=2008-01-06|author-link=Christopher Landsea}}</ref>

At the time, Hurricane Ava's minimum known pressure of {{convert|915|mbar|inHg|abbr=on}} was the lowest-known in its basin, making Ava the most intense [[Pacific hurricane]]. Ava is now the fifth-most intense, tied with [[Hurricane Ioke]], as hurricanes [[Hurricane Patricia|Patricia]], [[Hurricane Linda (1997)|Linda]], [[Hurricane Rick (2009)|Rick]] and [[Hurricane Kenna|Kenna]] recorded lower pressures.<ref name="EPAC HURDAT"/> However, Linda's and Rick's pressures were only estimated from satellite imagery,<ref name=Linda>{{cite web|url=http://www.nhc.noaa.gov/1997linda.html|title=Preliminary Report Hurricane Linda|date=1997-10-25|author=Max Mayfield|access-date=2008-01-06|publisher=National Hurricane Center}}</ref> so Ava held the record for lowest ''measured'' pressure until [[Hurricane Kenna|Kenna]] surpassed it in 2002.<ref>{{cite report|author=Richard J. Pasch|publisher=[[National Hurricane Center]]|date=October 23, 2015|access-date=October 23, 2015|title=Hurricane Patricia Discussion Number 14|url=http://www.nhc.noaa.gov/archive/2015/ep20/ep202015.discus.014.shtml|location=Miami, Florida}}</ref> However, the meteorological record for the eastern north Pacific are unreliable because geostationary satellite observation did not begin until 1966.<ref name=Linda/> Ava's pressure record is itself incomplete; Ava was only a Category&nbsp;4 when its {{convert|915|mbar|inHg|abbr=on}} pressure was measured, and the only reading from when it was a Category&nbsp;5 hurricane is {{convert|928|mbar|inHg|abbr=on}}.<ref name="Unisys data">{{cite web|url=http://www.weather.unisys.com/hurricane/e_pacific/1973/AVA/track.dat|publisher=Unisys|title=Hurricane AVA|access-date=2008-01-06|archive-url=https://web.archive.org/web/20131113143242/http://weather.unisys.com/hurricane/e_pacific/1973/AVA/track.dat|archive-date=2013-11-13|url-status=dead}}</ref> These two factors mean that Ava's lowest pressure may be below {{convert|915|mbar|inHg|abbr=on}}, and that there may be other cyclones stronger than Ava.<ref name=Guillermo>{{cite web|url=https://www.nhc.noaa.gov/data/tcr/EP091997_Guillermo.pdf|title=Preliminary Report Hurricane Guillermo|date=1997-10-02|author=Max Mayfield|publisher=National Hurricane Center|access-date=2018-10-07}}</ref>

==See also==
{{Portal|Tropical cyclones}}
* [[List of Pacific hurricanes]]
* [[Hurricane Linda (1997)]] – Surpassed the record of most intense Pacific hurricane after Ava
* [[Hurricane Patricia]] (2015) – Strongest and most intense Pacific hurricane on record, smashing the record held by both Ava and Linda

==References==
{{Reflist|2}}

==External links==
* [http://www.nhc.noaa.gov/ National Hurricane Center]

{{Category 5 Pacific hurricanes}}
{{1973 Pacific hurricane season buttons}}
{{Good article}}

[[Category:1973 Pacific hurricane season|Ava]]
[[Category:Hurricanes in California|Ava]]
[[Category:Category 5 Pacific hurricanes|Ava (1973)]]
[[Category:1973 in California]]
[[Category:1973 natural disasters in the United States]]