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The record breakingly active Central Pacific season continues with the formation of Tropical Depression 07C, 400 miles south of the Big Island of Hawaii. Convection is persistant over the LLCC, with banding features becoming more prominent. If this organisational trend continues, 07C will soon be a tropical storm. Strengthening is forecast as shear is low and waters very warm along track. 07C is expected to become a hurricane in 2-3 days time.

07C is currently heading northeastwards slowly as a trough to the north has a weak steering influence on 07C. This trough will be replaced by a ridge in a couple days time, allowing 07C to turn northwestwards. This ridge is only expected to temporarily influence 07C, and a turn back to the northeast is then expected on 4-5 days time, to the southeast of Hawaii. This is a fairly unusual track, and changes will more than likely occur as the steering environment is complex.

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07C has become Tropical Storm Oho, with winds of 35kts. Quite often, we will only use 1 name in a year, sometimes we will go a couple years without a named storm in the Central Pacific. Oho is the 8th named storm of the Central Pacific 2015 season. Amazing!

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Oho has moved very little in the last 36hrs, and has been meandering on the spot pretty much. An acceleration to the northeast is expected soon as a digging trough to the northwest eventually gets close enough to Oho to increase the steering currents. The track still takes Oho well to the southeast of Hawaii, so impact shouldn't be severe unless there are changes.

Moderate shear has plagued Oho over the last couple days, which was unforseen. Therefore, only slight intensification has occured, with winds of 45kts. Shear is expected to temporarily ease later roday and through the first half of tomorrow, allowing some further intensification. Oho however, is no longer forecast to become a hurricane, and instead is forecast to peak at 55kts. Thereafter, in about 36hrs time, the trough responsible for taking Oho northeastwards will become close enough to not only do that, but to increase she shear over Oho again, causing weakening.

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Oho is moving northeastwards at a faster pace. Shear has reduced over the system, which has allowed a central dense overcast and the beginnings of an eye to take shape. Oho has therefore been upgraded to a hurricane with winds of 65kts. A little further intensification is expected in the next 24hrs, before shear rises and waters cool along track.

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Oho is moving northeastwards at a faster pace. Shear has reduced over the system, which has allowed a central dense overcast and the beginnings of an eye to take shape. Oho has therefore been upgraded to a hurricane with winds of 65kts. A little further intensification is expected in the next 24hrs, before shear rises and waters cool along track.

 

So much for the 'little intensification' part that the Central Pacific Hurricane Center forecasted. Apparently this extremely active hurricane season just does not know how to stop, now throwing in another surprise. The latest satellite image suggests that Oho is undergoing a period of rapid intensification (RI), with an eye becoming apparent in Dvorak satellite imagery:

 

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Dvorak satellite image of Oho. Courtesy: NOAA.

 

Note how Oho has a spot of no convection surrounded by very intense convection in the eyewall, especially on the southern half of the system. Also nice to see the north-south orientation of the bands associated with Oho.

 

Probably this RI will be short lived, as sea surface temperatures should drop off sharply to the north of the system (where it is tracking towards), and shear should increase as well. Yet, it remains a very impressive burst of intensification in a relentlessly active hurricane season.

 

Sources:

http://www.prh.noaa.gov/cphc/

http://www.ssd.noaa.gov/PS/TROP/floaters/07C/07C_floater.html

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Indeed Vorticity, winds are now at 90kts, which is cat 2 on the SS scale. Interesting how quiet the Eastern Pacific has been recently, with all the activity focussed on the Central Pacific. Oho has certainly been impressive, could it get even stronger I wonder? Time is running out.

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Oho peaked at 95kts, just shy of Major Hurricane status. The hurricane is now rapidly losing organisation due to very high shear and passage over much colder waters. Oho should continue to gain lattitude very quickly and will likely soon become extratropical whilst moving into the waters west of Canada.

A bizarre track for a Central Pacific storm. There is a chance that Oho will remain tropical long enough to cross 140°, moving into the Eastern Pacific basin. IF it does, then Oho may well be the first Central Pacific named system to cross into the Eastern Pacific.

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