The Northern Hemisphere Tropics are very active as August comes to a close


A series of tropical cyclones in both the Atlantic and the West Pacific have wreaked havoc over the past two weeks. These included such storms as Hurricane Gordon that hit the Azores bringing gusts to 81mph, Tropical storm Helene that moved ashore in Mexico bringing deadly flash flooding there and in Central America, Typhoon Kai-Tak that exacerbated flooding in the Philippines and produced typhoon strength winds in southern China, and Typhoon Tembin making landfall in Taiwan’s less densely populated area with 120mph winds.

We are still tracking Tropical Storm Isaac that blew through the Caribbean dumping heavy rains and producing some minor wind damage from 70mph winds during its landfall in Haiti. Almost two dozen people are reported to have died as a result of Isaac so far in the Caribbean.

Tropical storm conditions and heavy rains occurred in Southern Florida as the storm passed through the Florida Straights. Isaac is now in the Eastern Gulf of Mexico and the latest suite of forecast models is suggesting a landfall in Southeastern Louisiana as a moderate hurricane. Hurricane and Tropical Storm warnings are up for the very real  threat of a serious storm surge and further fresh water flooding from >12 inches of rain along the northern Gulf of Mexico coast including; Louisiana, Mississippi, Alabama, and Florida. In addition tropical storm force and hurricane force winds are likely to be observed near the core of Isaac as it comes ashore, while tornadoes are possible in the outer bands of the storm that extend 200-300 miles from this core. Isaac will test many infrastructures put in place since Hurricane Katrina 7 years ago and Gustav four years ago. Isaac is a deep tropical storm that could become a hurricane this evening; hurricane hunters are investigating the storm to see if it has indeed strengthened I will have an update for the 8pm Eastern advisory.

Typhoon Tembin just before landfall in southern Taiwan on the 24th of August 2012. Taiwan’s Central Weather Bureau

Typhoon Tembin formed in the West Pacific and struck Southern Taiwan as a category three equivalent Typhoon with 120mph winds. The storm emerged into the south China Sea where it remains as it slowly moves to the northeast. Tembin is currently experiencing moderate northeasterly wind shear due to the upper level outflow from Typhoon Bolaven, as a result Tembin has weakened to a Tropical Storm, and could hit Taiwan again later this week before following Bolaven northwards towards the Korean Peninsula and Japan.

The center of Typhoon Bolaven over Nago, Okinawa as seen from Japan Meteorological Agency radar 9pm JST August 26th 2012.

Typhoon Bolaven formed from  large deep monsoon trough over the Marianas Islands. This typhoon slowly strengthened as it headed west-northwest to northwest for almost a week. Recently, Bolaven made it to category four equivalent strength with 145mph winds. Fortunately, some dry air made it into the storm’s core and concentric eye-walls suggested an eye wall replacement cycle was beginning. This happened as Bolaven crossed the island of Okinawa – it had only weakened to 120-130mph. An observing station in Nago, Okinawa reported a minimum pressure of in its hourly reports 935mb – it was likely lower than that in between reports.  Bolaven continues to weaken as it heads northwards towards the Korean Peninsula for a landfall late Tuesday August 28th.

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