{"id":69701,"date":"2026-03-29T18:59:00","date_gmt":"2026-03-29T18:59:00","guid":{"rendered":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/?p=69701"},"modified":"2026-04-06T00:49:03","modified_gmt":"2026-04-06T00:49:03","slug":"1-minute-goes-18-images-to-monitor-the-potential-of-heavy-rainfall-across-american-samoa","status":"publish","type":"post","link":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/archives\/69701","title":{"rendered":"1-minute GOES-18 images to monitor the potential of heavy rainfall and flooding across American Samoa"},"content":{"rendered":"

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1-minute GOES-18 Infrared Window (10.3 \u00b5m) images with an overlay of 1-minute GLM Flash Points (white dots), with plots of METAR surface reports (cyan), from 0801-1800 UTC on 29 March [click to play MP4 animation]<\/p><\/div>During a period when American Samoa had been under a prolonged Flood Watch<\/strong><\/a>, the Weather Service Office at Pago Pago<\/strong><\/a> requested that a GOES-18 (GOES-West)<\/em> Mesoscale Domain Sector<\/strong><\/a> be positioned over the region (due to their lack of radar). 1-minute Infrared imagery with GLM<\/strong><\/a> Flash Points (above)<\/strong><\/em> displayed deep convection with intermittent lightning activity that moved southward across the main island of Tutuila (where Pago Pago, METAR identifier NSTU, is located) and the smaller Manu’a Islands (~65 miles to the east) during a 10-hour period on 29 March 2026. The development of rain showers and thunderstorms was enhanced by the presence of a surface trough of low pressure that was draped across the Samoan islands (surface analyses: 0600 UTC<\/strong><\/a> | 1230 UTC<\/strong><\/a> | 1500 UTC<\/strong><\/a> | 1800 UTC<\/strong><\/a>).<\/p>\n

Rawinsonde data from Pago Pago (below)<\/strong><\/em> revealed that the atmosphere was rather moist and unstable, with parameters that were favorable for the development of deep convection. The coldest cloud-top infrared brightness temperature exhibited by storms in the vicinity of NSTU was -78\u00baC — which represented a small overshoot of the Most Unstable (MU) air parcel’s Equilibrium Level (EL).<\/p>\n

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Plot of rawinsonde data from Pago Pago, American Samoa at 1200 UTC on 29 March [click to enlarge]<\/p><\/div>Although rainfall across American Samoa on 29 March was not exceptionally heavy (and no Flash Flood Warnings were issued), there was a period when NSTU received 1.11″ of rain within about 2 hours as a thunderstorm with moderate rain showers passed over Tutuila (below)<\/em><\/strong>.<\/p>\n

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List of decoded surface reports from Pago Pago (NSTU), with a red box highlighting the period (in Local Time) that 1.11″ of rainfall occurred within about 2 hours on 29 March [click to enlarge]<\/p><\/div>
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List of METAR reports from Pago Pago (NSTU), with a red box highlighting the period when 1.11″ of rainfall occurred within about 2 hours on 29 March [click to enlarge]<\/p><\/div><\/p>\n","protected":false},"excerpt":{"rendered":"

During a period when American Samoa had been under a prolonged Flood Watch, the Weather Service Office at Pago Pago requested that a GOES-18 (GOES-West) Mesoscale Domain Sector be positioned over the region (due to their lack of radar). 1-minute Infrared imagery with GLM Flash Points (above) displayed deep convection with intermittent lightning activity that […]<\/p>\n","protected":false},"author":18,"featured_media":69717,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[76,114,16],"tags":[],"class_list":["post-69701","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-glm","category-goes-18","category-heavy-rain-flooding"],"acf":[],"_links":{"self":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/69701","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/users\/18"}],"replies":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/comments?post=69701"}],"version-history":[{"count":23,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/69701\/revisions"}],"predecessor-version":[{"id":69725,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/posts\/69701\/revisions\/69725"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media\/69717"}],"wp:attachment":[{"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/media?parent=69701"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/categories?post=69701"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cimss.ssec.wisc.edu\/satellite-blog\/wp-json\/wp\/v2\/tags?post=69701"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}