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Global Tropics Turn Active

By: Chief Meteorologist Eric Fisher
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climo Global Tropics Turn Active

The climatological peak of hurricane season is a sharp one, and it starts to ramp up now. Source: NOAA and the National Hurricane Center

August hits, and it’s like someone turned on a light. It’s pretty amazing how well-oiled of a machine our world can be, and it never ceases to amaze me that this time of year, everything in the tropics starts spinning. Sure there may be a straggler early in the season here and there, but August (especially mid-August) through September features the sharp peak of hurricane season. During this short window, the tropics light up with spinning collections of thunderstorms over warm water. And then just like that, the switch typically gets flicked to the ‘off’ position as we head deeper into fall.

bertha Global Tropics Turn Active

Bertha as seen from space on Monday evening. The center of circulation is right along the 30th parallel, and as you can see it doesn’t have many thunderstorms surrounding it! Source: NOAA

One cue, things are quite active right now around the world! Closest to us here at home is Bertha, which isn’t looking so hot. I’m amazed the NHC kept this rather disorganized blob of convection a hurricane Monday afternoon. Its center of circulation was completely exposed! Not sure I’ve seen many hurricanes like that before. Be that as it may, Bertha is going to pose little threat to the East Coast. It *may* add some tropical moisture to the atmosphere here on Wednesday, enhancing rainfall in any storms that develop (those storms being sparked by a cold front, not Bertha). Other than that – it’s mainly a fish storm with some enhanced surf issues. We’ll get 5-7′ swells here in New England Tuesday night through Wednesday night, and swimmers will have to be very careful in the water due to rip currents. Then Bertha will race farther out to sea, of interest to shipping lanes only.

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There are, however, some interesting stats on Bertha. For one, it’s right on time. The average date for the 2nd named storm of the Atlantic season is July 29th. Bertha received its name on July 31st. Bertha is also the earliest we’ve had the second hurricane of a season since 2008 (Dolly). There have been quite a few ‘quiet’ years since the incredible seasons of 2004 and 2005 in the Atlantic. It’s also the first time the ‘A’ and ‘B’ storms of the season have become hurricanes since 1992. Of course, the ‘A’ storm that year is infamous. It’s when Andrew made landfall; one of the worst hurricanes to ever strike the U.S.

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Satellite capture over the eastern/central Pacific on Monday afternoon. Source: NOAA

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Watch mesovortices swirl within the eye of Category 4 hurricane Iselle! Source: CIMSS Satellite Blog

Let’s switch basins, and move on over to the Eastern Pacific. This is where two very intriguing storms are spinning. Leading the charge is Iselle, a monstrous and powerful Category 4 hurricane as of this writing. Iselle is about to do something rather rare – head directly toward Hawaii. Hawaii is not a stranger to tropical storms – many of these systems don’t hold on to their hurricane strength as they make their final approach due to cooler waters. But if Iselle can hold on as a hurricane until landfall, it’d be the first to do so since Iniki in 1992 (an infamous year for tropical systems it would seem). Iniki is the most damaging hurricane to strike Hawaii in recent memory, making landfall as a Category 4. It killed six, destroyed approximately 1,500 homes, and produced an estimated $1.8 billion in damage. Another interesting fact on Iniki – it made landfall as Stephen Spielberg was shooting ‘Jurassic Park’ on Kauai! That stormy footage at the end of the film is actually Iniki blowing through. Other major storms over the past ~60 years include Iwa, Dot and Nina.

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Official forecast track for Iselle from the NHC, as of 2pm PDT Monday.

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Iselle as seen from space. Source: NOAA

Iselle is not expected to be as strong as these infamous storms,  but will likely bring strong winds and a significant flash flooding risk late this week. The current NHC forecast track has Iselle making landfall Thursday afternoon.

cpac cdas1 Global Tropics Turn Active

Current SST’s in the eastern Pacific. Iselle and Julio are traveling along the 26ºC isotherm…or about 78-79ºF. Source: WeatherBell

Behind Iselle is Julio, and this is where the plot thickens. Julio is likely to become a hurricane and follow in Iselle’s footsteps. That’s actually one factor not working in Julio’s favor – it will have to travel over the same water that Iselle is currently churning up. When a storm passes over the ocean, it produces ‘upwelling’ – bringing cooler water temps to the surface. The water here is already borderline for attaining and holding on to hurricane strength. It’s likely Julio won’t become quite as strong, or make landfall with the same intensity. But back-to-back systems making landfall in Hawaii within a week’s time would be extremely rare. I can’t find a situation where that’s happened before on record.

There’s one more storm out here, so far out that it’s actually moved into the Central Pacific. Genevieve become a Tropical Depression again on Monday morning, but is of limited threat to any land.

halong Global Tropics Turn Active

Current forecast track/intensity for Halong, from the JTWC

Let’s go so far west that we end up in the far east – south of Japan. That’s where we find Halong. Halong is a typhoon that will be heading northward this week. It’s expected to pass just east of Okinawa (according to the Joint Typhoon Warning Center) and then make landfall in southern Japan by Friday. Thankfully, Halong should lose its punch during its travels north. The current forecast has it making landfall with the equivalent strength of a Category 1 hurricane before quickly weakening further.

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