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Typhoon Muifa Expected to Strike Okinawa, Japan – August 1st, 2011

24.1N 131.7E

August 1st, 2011 Category: Image of the day, Tropical Cyclones

Typhoon Muifa (TY 11W) - July 28th, 2011

Enhanced image

Track of TY 11W - July 31st, 2011 © Univ. of Wisconsin

Track of TY 11W

Typhoon Muifa (TY 11W), located approximately 570 nm south-southeast of Kadena air base, Japan, has tracked northward at 08 knots over the past six hours. A distinct 10 nm eye persists, and animated infrared imagery shows a recent trend toward better organization and consolidation of the convection around the system center. Maximum significant wave height is 46 feet.

Overall though, there is not much change in intensity, which continue to be based on agency subjective Dvorak assessments. Over the past 24 hours, the overall system intensity has come down 20 knots. Despite its severe intensity, TY 11W is showing diurnal intensity fluctuation. For the second consecutive day, convection waned during the daylight hours and surged during the evening hours.

Some erosion of the eyewall over the northeast quadrant occurred during the daylight ebb, but the latest available microwave imagery indicates that deep convection persists throughout the storm. The outflow situation also deteriorated during the past 24 hours, but it too is starting to improve.

Animated water vapor imagery shows an east-west oriented trough impinging on the northeastern quadrant beginning near 310000z. The trough is currently stretched along the 24th latitude and is now suppressing outflow over the northwestern quadrant. The 311200z PGTW upper level streamline analysis also reveals increased sheer over the northwest quadrant. Although the trough is impeding on the northwestern quadrant, it is enhancing outflow over the northeast quadrant. A vigorous poleward channel has set up over the northeastern sector. Equatorward outflow remains vigorous and convection over the entire southern semicircle is widespread and deep. Recent imagery confirms gale force winds extend approximately 170 nm outward over the southern semicircle.

Muifa continues its poleward track through a broad weakness in the subtropical ridge. The weakness exists between the seasonal anticyclone over eastern China and the Bonin High, which is now retrograding southeast. The slow and erratic poleward movement will continue through approximately 20 degrees north latitude (TAU 18), and then the anticyclone will begin nudging the system on a bend to the northwest. Intensity guidance indicates that the highest shear will be encountered during the next 18 hours, just before the storm makes its westward bend. aAbove 20 degrees north latitude, vertical wind shear is expected to stay at around 15 knots, while sea surface temperatures will remain near 29 degrees through the entire track.

Ocean heat content remains the primary variable in the intensity forecast. Although sea surface temperatures remain high, the depth of the 26 degree isotherm decreases by nearly 50 per cent north of 20 degrees north latitude. Track guidance continues to come into tighter alignment. All aids indicate a high impact strike on or very close to Okinawa.

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