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Somerset Squall

Hurricane Greg

Another tropical depression has formed, this time off the south coast of Mexico. Intensity is 30kts. 07E is currently suffering some moderate shear which giving the depression a rather lop-sided look at present. Shear is set to lessen over the coming days, and 07E will be moving over the warmest waters of the basin (30+C). NHC forecast 07E to become a hurricane (yes, another one!), with a peak of 70kts. However, if the shear eases more than forecast, 07E could strengthen rapidly, and become a lot stronger than this. We shall see as always!

07E is expected to head on a typical west-northwesterly track through it's lifetime and once it moves away from Mexico, it shouldn't be a threat to land.

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07E has been upgraded to Tropical Storm Greg, with intensity rising to 45kts. Greg has formed a slightly irregular central dense overcast feature despite the moderate shear impinging on the storm. With this in mind, Greg should continue to strengthen over the next few days and will likely become a hurricane. Just how strong is open to question, but as I said previously, if the shear eases completely then the NHC's intensity could be a little conservative. We shall see.

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MIAMI—

Forecasters said late Wednesday that Hurricane Greg has formed off Mexico's Pacific coast, but no watches or warnings were issued.

The U.S. National Hurricane Center in Miami said the Category 1 storm had maximum sustained winds near 75 mph. It was centered about 280 miles west-southwest of Manzanillo, Mexico. It's nearly 400 miles south-southeast of the southern tip of Baja, California.

Forecasters say it is on a generally northwest track out to sea that will keep its center well away from land. There are no oil installations in the path of the hurricane.

Meanwhile, farther out in the Pacific, Tropical Storm Fernanda was moving slowly west-northwest and strengthening a little. The storm's maximum sustained winds remained near 60 mph.

http://www.latimes.com/news/nationworld/world/la-fgw-hurricane-greg-20110818,0,1423530.story

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Greg is now a Category 1 hurricane and Greg is expected to intensify to Category 2 while moving WNW-ard.

As Greg moves over colder waters,it will turn westward and dissipate.

Discussion from NHC ---->

late afternoon visible satellite images showed a banding eyefeature that became obscured as new convection developed nearthe center around sunset. The small eye feature was also evidentin a 2025 UTC trmm overpass. Unfortunately...there has been noadditional microwave imagery since that time. Although Dvorak finalT-numbers from TAFB and SAB were 4.0 and 3.5...respectively...thedata T-numbers from both agencies were 4.0. This supportsincreasing the wind speed to 65 kt. Greg becomes the sixthhurricane in the eastern Pacific basin in 2011.

Sea surface temperatures along the path of Greg gradually coolthroughout the forecast period...however the cyclone is forecastto remain over 27-28 degree celsius water for another 24 hours orso. During that time...shear is expected to remain light whichshould allow for additional strengthening. The updated forecastindicates a peak intensity of 85 kt in 24 hours and is in bestagreement with the SHIPS/lgem guidance. Thereafter...steadyweakening is shown as Greg is forecast to move over decreasingSSTs.

The initial motion remains a brisk 285/19. Greg continues to besteered quickly west-northwestward between a large mid/upper-levelridge over the southern United States and a cyclonic gyre to thesouthwest of the cyclone. As the gyre weakens during the next 24hours...Greg should turn westward and slow down. The westernportion of the ridge is forecast to weaken in a couple of days as atrough approaches the West Coast of the United States. This shouldresult in a further reduction of forward speed. The models are ingood agreement on this scenario...but the latest guidance envelopehas shifted southward at 72 hours and beyond. This requires asouthward adjustment to the track in the latter portion of theforecast period.

Forecast positions and Max winds

init 18/0300z 17.5n 108.3w 65 kt 75 mph 12h 18/1200z 18.1n 110.8w 75 kt 85 mph 24h 19/0000z 18.6n 113.4w 85 kt 100 mph 36h 19/1200z 18.9n 115.4w 75 kt 85 mph 48h 20/0000z 19.0n 117.5w 65 kt 75 mph 72h 21/0000z 19.0n 120.0w 50 kt 60 mph 96h 22/0000z 19.0n 122.5w 35 kt 40 mph120h 23/0000z 19.0n 124.5w 25 kt 30 mph...Post-trop/remnt low

$$forecaster Brown

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Greg has continued to strengthen this afternoon and is now a 75kt hurricane. Greg has a small central dense overcast feature with a fleeting eye and impressive banding features in the southern quadrant. A little more intensification is possible before sea temps decline which will initiate a weakening trend.

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HURRICANE GREG DISCUSSION NUMBER 9

NWS NATIONAL HURRICANE CENTER MIAMI FL EP072011

200 PM PDT THU AUG 18 2011

GREG HAS CHANGED LITTLE IN ITS APPEARANCE ON SATELLITE IMAGERY IN

THE PAST SIX HOURS WITH OCCASIONAL HINTS OF AN EYE APPEARING IN

VISIBLE IMAGERY. OUTFLOW REMAINS GOOD OVER THE SOUTHWESTERN

SEMICIRCLE AND RATHER POOR TO THE NORTHEAST. AS A RESULT OF THIS

AND POSSIBLE DRY AIR ENTRAINMENT...THE CORE OF THE SYSTEM IS

DETACHED FROM THE DEEP CONVECTIVE BAND TO THE SOUTHEAST AND SOUTH.

INTENSITY ESTIMATES FROM TAFB AND SAB BOTH CAME IN AT 77 KT...AND

THE INITIAL INTENSITY HAS BEEN HELD AT 75 KT.

THE INITIAL MOTION IS 285/12 WHICH IS SLIGHTLY SLOWER THAN SIX HOURS

AGO. GREG REMAINS LOCATED BETWEEN A LARGE MID- TO UPPER-LEVEL RIDGE

EXTENDING FROM THE NORTHEAST PACIFIC OFF NORTHERN CALIFORNIA TO

NORTHWESTERN MEXICO AND A LARGE GYRE IN THE INTERTROPICAL

CONVERGENCE ZONE TO ITS SOUTHWEST. MOST DYNAMICAL MODELS FORECAST

GREG TO SLOW AND MAKE A GRADUAL TURN TO THE WEST IN THE NEXT 24 TO

48 HOURS AS THE NORTHEAST PACIFIC RIDGE REMAINS IN PLACE AND GREG

INTERACTS WITH THE WEAK GYRE TO ITS SOUTHWEST. BEYOND 48 HOURS THE

TRACK HAS BEEN NUDGED SLIGHTLY TO THE SOUTH TO BE IN BETTER

AGREEMENT WITH THE CONSENSUS MODELS.

THE INTENSITY OF GREG HAS LIKELY PLATEAUED AND IS NOT EXPECTED TO

CHANGE MUCH IN THE NEXT 12 HOURS. BEYOND 12 HOURS...GREG IS

FORECAST TO MOVE OVER INCREASINGLY COOLER WATERS WHICH WILL CAUSE

STEADY WEAKENING. GREG IS FORECAST TO BECOME A POST-TROPICAL

REMNANT LOW IN ABOUT 5 DAYS. THE FORECAST INTENSITIES HAVE BEEN

NUDGED DOWNWARD FROM THE PREVIOUS FORECAST TO BE IN BETTER

AGREEMENT WITH GUIDANCE.

FORECAST POSITIONS AND MAX WINDS

INIT 18/2100Z 18.8N 112.6W 75 KT 85 MPH

12H 19/0600Z 19.0N 114.6W 75 KT 85 MPH

24H 19/1800Z 19.1N 116.9W 70 KT 80 MPH

36H 20/0600Z 19.1N 119.0W 60 KT 70 MPH

48H 20/1800Z 18.9N 120.7W 50 KT 60 MPH

72H 21/1800Z 18.5N 123.0W 35 KT 40 MPH

96H 22/1800Z 18.5N 125.5W 25 KT 30 MPH

120H 23/1800Z 18.0N 128.0W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$

FORECASTER BEVEN/WROE

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Greg has lost hurricane status with intensity now at 55kts. Cool waters are causing a reduction in the depth of convection, and even cooler waters lie ahead on track. Therefore, further weakening is expected with Greg degenerating into a remnant low in about 48hrs time.

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Greg continues to weaken as it traverses waters of about 23C and enters a drier, more stable airmass. Convection is limited to a small cluster of thunderstorms over the LLC. Intensity has been reduced to 35kts. Greg should continue to weaken and degenerate into a remnant low.

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Convection has failed to materialise over Greg's LLC over the last 12hrs. Therefore, it has been declared a remnant low. Re-generation is not expected as waters remain at 22C and the air remains dry on the westward heading. The remnant low should dissipate in a couple of days.

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