Hurricane Sam: Difference between revisions
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Intensification was initially slow; the cyclone's center was still attached to the northern edge of a low-pressure [[trough (meteorology)|trough]] and the former's surface circulation was only narrowly closed.<ref>{{cite report |last1=Berg |first1=Robbie |title=Tropical Depression Eighteen Discussion Number 2 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.002.shtml? |publisher=National Hurricane Center |access-date=5 October 2021 |date=23 September 2021 |archive-date=6 October 2021 |archive-url=https://web.archive.org/web/20211006000545/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.002.shtml |url-status=live }}</ref> Although the depression had curved [[rainband]]s across its northern and western sides, dry air was entraining across its eastern flank.<ref>{{cite report |last1=Cangialosi |first1=John |title=Tropical Depression Eighteen Discussion Number 3 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.003.shtml? |publisher=National Hurricane Center |access-date=5 October 2021 |date=23 September 2021 |archive-date=23 September 2021 |archive-url=https://web.archive.org/web/20210923235134/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.003.shtml |url-status=live }}</ref> The depression was upgraded to ''Tropical Storm Sam'' at 15:00 UTC on September 23, after its structure improved significantly on both [[satellite image|satellite]] and [[microwave imaging|microwave imagery]]; the latter showed a banding feature wrapping around 75 percent of the center. The combination of a favorable environment, Sam's structural improvement, and the alignment of the cyclone's low- and mid-level centers signaled that [[rapid intensification]] was imminent.<ref>{{cite report |last1=Papin |first1=Philippe |title=Tropical Storm Sam Discussion Number 4 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.004.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=23 September 2021 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924101044/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.004.shtml |url-status=live }}</ref> The storm rapidly intensified shortly after, with an eyewall forming on microwave imagery,<ref>{{cite report |last1=Berg |first1=Robbie |title=Tropical Storm Sam Discussion Number 6 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.006.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924043551/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.006.shtml |url-status=live }}</ref> as well as, banding features that wrapped around most of its center. Sam became a [[Saffir-Simpson Scale|Category 1 hurricane]] around 09:00 UTC on September 24.<ref>{{cite report |last1=Cangialosi |first1=John |title=Hurricane Sam Discussion Number 7 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.007.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=25 September 2021 |archive-url=https://web.archive.org/web/20210925002103/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.007.shtml |url-status=live }}</ref> |
Intensification was initially slow; the cyclone's center was still attached to the northern edge of a low-pressure [[trough (meteorology)|trough]] and the former's surface circulation was only narrowly closed.<ref>{{cite report |last1=Berg |first1=Robbie |title=Tropical Depression Eighteen Discussion Number 2 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.002.shtml? |publisher=National Hurricane Center |access-date=5 October 2021 |date=23 September 2021 |archive-date=6 October 2021 |archive-url=https://web.archive.org/web/20211006000545/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.002.shtml |url-status=live }}</ref> Although the depression had curved [[rainband]]s across its northern and western sides, dry air was entraining across its eastern flank.<ref>{{cite report |last1=Cangialosi |first1=John |title=Tropical Depression Eighteen Discussion Number 3 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.003.shtml? |publisher=National Hurricane Center |access-date=5 October 2021 |date=23 September 2021 |archive-date=23 September 2021 |archive-url=https://web.archive.org/web/20210923235134/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.003.shtml |url-status=live }}</ref> The depression was upgraded to ''Tropical Storm Sam'' at 15:00 UTC on September 23, after its structure improved significantly on both [[satellite image|satellite]] and [[microwave imaging|microwave imagery]]; the latter showed a banding feature wrapping around 75 percent of the center. The combination of a favorable environment, Sam's structural improvement, and the alignment of the cyclone's low- and mid-level centers signaled that [[rapid intensification]] was imminent.<ref>{{cite report |last1=Papin |first1=Philippe |title=Tropical Storm Sam Discussion Number 4 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.004.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=23 September 2021 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924101044/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.004.shtml |url-status=live }}</ref> The storm rapidly intensified shortly after, with an eyewall forming on microwave imagery,<ref>{{cite report |last1=Berg |first1=Robbie |title=Tropical Storm Sam Discussion Number 6 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.006.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924043551/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.006.shtml |url-status=live }}</ref> as well as, banding features that wrapped around most of its center. Sam became a [[Saffir-Simpson Scale|Category 1 hurricane]] around 09:00 UTC on September 24.<ref>{{cite report |last1=Cangialosi |first1=John |title=Hurricane Sam Discussion Number 7 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.007.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=25 September 2021 |archive-url=https://web.archive.org/web/20210925002103/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.007.shtml |url-status=live }}</ref> |
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Sam's strengthening then halted for a brief period as dry air degraded the western portion of its core.<ref>{{cite report |last1=Papin |first1=Philippe |title=Hurricane Sam Discussion Number 8 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.008.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2018 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924154631/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.008.shtml |url-status=live }}</ref> The cyclone began to intensify again late on September 24 as the dry air's influence lessened, however, microwave imagery displayed concentric eyewalls, indicating that Sam was undergoing an [[eyewall replacement cycle]]. The storm continued to track west-northwest, however, its forward speed began to decrease as a result of the mid-level ridge moving to the northwest of Sam.<ref>{{cite report |last1=Papin |first1=Philippe |title=Hurricane Sam Discussion Number 9 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.009.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=5 October 2021 |archive-url=https://web.archive.org/web/20211005185405/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.009.shtml |url-status=live }}</ref> |
Sam's strengthening then halted for a brief period as dry air degraded the western portion of its core.<ref>{{cite report |last1=Papin |first1=Philippe |title=Hurricane Sam Discussion Number 8 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.008.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2018 |archive-date=24 September 2021 |archive-url=https://web.archive.org/web/20210924154631/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.008.shtml |url-status=live }}</ref> The cyclone began to intensify again late on September 24 as the dry air's influence lessened, however, microwave imagery displayed concentric eyewalls, indicating that Sam was undergoing an [[eyewall replacement cycle]]. The storm continued to track west-northwest, however, its forward speed began to decrease as a result of the mid-level ridge moving to the northwest of Sam.<ref>{{cite report |last1=Papin |first1=Philippe |title=Hurricane Sam Discussion Number 9 |url=https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.009.shtml? |publisher=National Hurricane Center |access-date=6 October 2021 |date=24 September 2021 |archive-date=5 October 2021 |archive-url=https://web.archive.org/web/20211005185405/https://www.nhc.noaa.gov/archive/2021/al18/al182021.discus.009.shtml |url-status=live }}</ref>Sam moves Northeast of the East Coast but is forecasted to make a impact on Iceland as a (post tropical cyclone). |
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Revision as of 22:06, 6 October 2021
This draft was originally created by @HurricaneResearch but was edited by@Hurricane Noah.
Category 4 major hurricane (SSHWS/NWS) | |
Formed | September 22, 2021 |
---|---|
Dissipated | Currently active |
(Extratropical after October 5) | |
Highest winds | 1-minute sustained: 155 mph (250 km/h) |
Lowest pressure | 929 mbar (hPa); 27.43 inHg |
Part of the 2021 Atlantic hurricane season |
Origins, development, and peak intensity
Hurricane Sam originated from a westward tracking tropical wave that departed from the western coast of Africa on September 19.[1] The National Hurricane Center (NHC) had first forecast the possibility of tropical development earlier that day.[2] Although thunderstorm activity was somewhat organized, the system lacked a closed surface circulation. Upper-level winds hindered the development of the system over the next day,[3][4] causing fluctuations in organization.[5][6] Thunderstorms became increasingly organized,[7] and an elongated low-level surface circulation developed on September 22. This led to the formation of a tropical depression around 21:00 UTC that day. At that time, a mid-level ridge located to the north and west was steering the system westward. The nascent depression was located in a favorable environment both below and aloft, with sea surface temperatures of 82–84 °F (28–29 °C) and low vertical wind shear.[8]
Intensification was initially slow; the cyclone's center was still attached to the northern edge of a low-pressure trough and the former's surface circulation was only narrowly closed.[9] Although the depression had curved rainbands across its northern and western sides, dry air was entraining across its eastern flank.[10] The depression was upgraded to Tropical Storm Sam at 15:00 UTC on September 23, after its structure improved significantly on both satellite and microwave imagery; the latter showed a banding feature wrapping around 75 percent of the center. The combination of a favorable environment, Sam's structural improvement, and the alignment of the cyclone's low- and mid-level centers signaled that rapid intensification was imminent.[11] The storm rapidly intensified shortly after, with an eyewall forming on microwave imagery,[12] as well as, banding features that wrapped around most of its center. Sam became a Category 1 hurricane around 09:00 UTC on September 24.[13]
Sam's strengthening then halted for a brief period as dry air degraded the western portion of its core.[14] The cyclone began to intensify again late on September 24 as the dry air's influence lessened, however, microwave imagery displayed concentric eyewalls, indicating that Sam was undergoing an eyewall replacement cycle. The storm continued to track west-northwest, however, its forward speed began to decrease as a result of the mid-level ridge moving to the northwest of Sam.[15]Sam moves Northeast of the East Coast but is forecasted to make a impact on Iceland as a (post tropical cyclone).
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See also
Notes
References
- ^ Brown, Daniel (20 September 2021). Tropical Weather Outlook: Atlantic [800 PM EDT Sun Sep 19 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 5 October 2021.
- ^ Hagen, Andrew; Latto, Andrew (19 September 2021). Tropical Weather Outlook: Atlantic [800 AM EDT Sun Sep 19 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 2 October 2021. Retrieved 5 October 2021.
- ^ Brown, Daniel (21 September 2021). Tropical Weather Outlook: Atlantic [800 PM EDT Mon Sep 20 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 2 October 2021. Retrieved 5 October 2021.
- ^ Brown, Daniel (22 September 2021). Tropical Weather Outlook: Atlantic [800 PM EDT Tue Sep 21 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 5 October 2021.
- ^ Papin, Philippe (21 September 2021). Tropical Weather Outlook: Atlantic [800 AM EDT Tue Sep 21 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 5 October 2021.
- ^ Papin, Philippe (21 September 2021). Tropical Weather Outlook: Atlantic [200 PM EDT Tue Sep 21 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 5 October 2021.
- ^ Papin, Philippe (22 September 2021). Tropical Weather Outlook: Atlantic [800 AM EDT Wed Sep 22 2021] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 5 October 2021.
- ^ Papin, Philippe (22 September 2021). Tropical Depression Eighteen Discussion Number 1 (Report). National Hurricane Center. Archived from the original on 24 September 2021. Retrieved 5 October 2021.
- ^ Berg, Robbie (23 September 2021). Tropical Depression Eighteen Discussion Number 2 (Report). National Hurricane Center. Archived from the original on 6 October 2021. Retrieved 5 October 2021.
- ^ Cangialosi, John (23 September 2021). Tropical Depression Eighteen Discussion Number 3 (Report). National Hurricane Center. Archived from the original on 23 September 2021. Retrieved 5 October 2021.
- ^ Papin, Philippe (23 September 2021). Tropical Storm Sam Discussion Number 4 (Report). National Hurricane Center. Archived from the original on 24 September 2021. Retrieved 6 October 2021.
- ^ Berg, Robbie (24 September 2021). Tropical Storm Sam Discussion Number 6 (Report). National Hurricane Center. Archived from the original on 24 September 2021. Retrieved 6 October 2021.
- ^ Cangialosi, John (24 September 2021). Hurricane Sam Discussion Number 7 (Report). National Hurricane Center. Archived from the original on 25 September 2021. Retrieved 6 October 2021.
- ^ Papin, Philippe (24 September 2018). Hurricane Sam Discussion Number 8 (Report). National Hurricane Center. Archived from the original on 24 September 2021. Retrieved 6 October 2021.
- ^ Papin, Philippe (24 September 2021). Hurricane Sam Discussion Number 9 (Report). National Hurricane Center. Archived from the original on 5 October 2021. Retrieved 6 October 2021.
This article incorporates public domain material from websites or documents of the National Weather Service.
External links
- The National Hurricane Center's advisory archive on Hurricane Sam