Invest 91L was reclassified as Subtropical Depression 01 by the National Hurricane Center (NHC) on Wednesday morning.\u00a0 At 11:00 a.m. EDT on Wednesday the center of Subtropical Depression 01 was located at latitude 31.9\u00b0N and longitude 40.9\u00b0W which put it about 890 miles (1435 km) west-southwest of the Azores.\u00a0 It was moving toward the north-northeast at 8 m.p.h.\u00a0 The maximum sustained wind speed was 35 m.p.h. (55 km\/h) and there were wind gusts to 45 m.p.h. (75 km\/h).\u00a0 The minimum surface pressure was 995 mb.<\/p>\n
This system was designated Invest 91L when showers and thunderstorms began to form near the center of an old occluded extratropical cyclone.\u00a0 The system began to separate from the occluded front and drift toward the south-southeast.\u00a0 A cut off upper level low associated with the original extratropical cyclone was rotating in a similar way to the circulation in the lower levels of Invest 91L.\u00a0 So, there was not a lot of vertical wind shear.\u00a0 The lack of wind shear allowed for the circulation to develop a more circular, tropical cyclone like shape.\u00a0 When Invest 91L drifted toward the south-southeast it moved over slightly warmer water.\u00a0 Additional energy from the ocean increased the number and strength of showers and thunderstorms.\u00a0 A primary rainband wrapped about half way around the center of circulation and additional bands formed on the eastern side of the circulation.\u00a0 The system developed more convection, a more circular shape and a wind field with the strongest winds closer to the center of circulation.\u00a0 However, it is still under an upper low with cooler air aloft and so the system has a hybrid structure.\u00a0 The hybrid structure and the lack of a well defined warm core is the reason NHC classified the system as a subtropical depression instead of designating it as a tropical depression.<\/p>\n
Subtropical Depression 01 is in an environment that would not be favorable for the intensification of a purely tropical cyclone.\u00a0 It is moving over water where the Sea Surface Temperature (SST) is near 21\u00b0C.\u00a0 However, with the upper level low limiting the vertical wind shear, the SST is warm enough to support some strengthening of a subtropical cyclone.\u00a0 The colder air in the upper low creates enough instability for showers and thunderstorms to develop even though they will not be as tall as they would be over warmer water in the tropics.\u00a0 If the maximum sustained wind speed increases to 40 m.p.h. (65 km\/h), then the system would become Subtropical Storm Arlene.\u00a0 Showers and thunderstorms would have to convert enough latent energy to internal energy to generate a warm core in the middle and upper levels in order for the system to be classified as a tropical cyclone.<\/p>\n
Subtropical Depression 01 is being steering by the upper level low underneath which it formed.\u00a0 The numerical models are forecasting a slow counterclockwise loop underneath the upper low during the next few days.\u00a0 Eventually, the models are forecasting that the upper low and subtropical depression will both move off toward the east.<\/p>\n","protected":false},"excerpt":{"rendered":"
Invest 91L was reclassified as Subtropical Depression 01 by the National Hurricane Center (NHC) on Wednesday morning.\u00a0 At 11:00 a.m. EDT on Wednesday the center of Subtropical Depression 01 was located at latitude 31.9\u00b0N and longitude 40.9\u00b0W which put it about 890 miles (1435 km) west-southwest of the Azores.\u00a0 It was moving toward the north-northeast […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3,2],"tags":[316,375,317,660,661,31,374,662,322],"_links":{"self":[{"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/posts\/3861"}],"collection":[{"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=3861"}],"version-history":[{"count":1,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/posts\/3861\/revisions"}],"predecessor-version":[{"id":3862,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=\/wp\/v2\/posts\/3861\/revisions\/3862"}],"wp:attachment":[{"href":"https:\/\/jayhobgood.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=3861"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=3861"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/jayhobgood.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=3861"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}