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Tropical Storm Danny


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If Danny were a more typical-sized cyclone and had another two days or so, it would potentially have enough time to become a substantial hurricane and form a large anticyclone overhead, potentially counteracting the moderate to strong TUTT-generated westerlies lurking to its northwest. However, Danny has less than 24 hours to go before it encounters those westerlies (strong vertical shear), thereby halting significant intensification in its tracks. You can already see signs of shear impinging on outflow in the western semicircle. Given the small size of the storm, I think that Danny will likely peak sometime later today or overnight before weakening rapidly starting tomorrow. The NHC shows a peak around 12Z tomorrow, based on a blend of the dynamic and statistical guidance, which I think is too late, given that the ECMWF already shows less favorable conditions and signs of weakening overnight.

 

Agreed. Difficult to see such a small storm thriving through what's ahead. There is a lot of shear and dry air in Danny's not-so-distant future. 

 

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Remember the days when a strengthening hurricane east of the islands used to survive past 60w?

I consider intensity forecasts post 72-hours with a grain of salt. Haven't look at the features closely but I imagine a slight alteration of the TUTT would allow for a different outcome.

 

Of course the future of Danny may be more dependent on interaction with Hispaniola.

 

gfs_shear_atl_11.png

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Highly unlikely with the now weaker storm.

Bill was a beast cat 3 with a huge area of hurricane fource winds in our swell window. It also had almost perfect wave setup as the track of the storm kept swell moving with the strongest winds leading to enhanced wave heights.

That swell was the biggest i have surfed on Long Island in 20 years of surfing. Easily 15 foot on the face. The craziest thing is the swell peaked over night so we never even saw the biggest.

The swell peaked at the Long Island bouy at around 20 feet at 20 seconds. Just not something you see on the east coast. And would easily have the Eddie running in Hawaii. (Better bottom an no continental shelf makes a swell that size break 40' plus)

 

Surfed that swell in OCMD. Easily one of the best swells I have ever surfed.

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Danny is definitely moving NW currently and appears to be showing some effects of Southerly shear at the moment. You can see how the outflow is slightly restricted in the SE quadrant. Hopefully the cyclone can escape far enough North to avoid the cyclone graveyard in the E Caribbean.

avn_lalo-animated.gif

On the last couple frames outflow on nw and sw quadrants seems to be slighlty improving.

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NHC stands pat at 11pm. 80mph, 990mb, WNW at 10mph

 

HURRICANE DANNY DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042015
1100 PM AST THU AUG 20 2015

Danny continues to produce a compact central dense overcast, and
cloud tops are a little colder than earlier due to a recent burst of
convection in the eyewall. Coincidentally, the convective canopy
has intermittently been obscuring the tiny eye that was observed
earlier today. The initial intensity remains 70 kt based on a blend
of subjective Dvorak satellite estimates of T4.0/65 kt from TAFB and
T4.5/77 kt from SAB.

The hurricane continues to move west-northwestward, or 295/9 kt,
toward a break in the subtropical ridge located northeast of the
Leeward Islands. The track guidance shows this motion continuing
for another 36 hours, with Danny then turning westward and
accelerating from 48 hours through day 5 while the ridge builds
westward north of the Greater Antilles. With the exception of the
GFDL, GFDN, and NAVGEM--which insist that Danny will turn
northwestward before reaching the Leeward Islands--the other track
models are in agreement on a future track near or just south of the
northern Leeward Islands and Greater Antilles. This clustering of
the guidance required no significant changes to the official NHC
track forecast on this advisory cycle.

As has been mentioned in earlier discussions, Danny is susceptible
to sudden and possibly unexpected changes in intensity due to its
small size. Since vertical shear is expected to remain low for
another 24 hours or so, Danny could certainly strengthen some more
if it can avoid intrusions of dry air into the inner core. After
36 hours, an increase in westerly to southwesterly shear and a
decrease in mid-level relative humidities are expected to lead to
weakening, and Danny is forecast to weaken to a tropical storm
before it reaches the Leeward Islands. The updated NHC intensity
forecast is very similar to the previous one and remains close to
the IVCN consensus. It should be noted that given Danny's small
size, the weakening rate after 36 hours could be faster than
indicated in the official forecast.

A NOAA aircraft will be conducting a research mission in and around
Danny Friday afternoon, and an Air Force Reserve Unit reconnaissance
aircraft will investigate Danny Saturday afternoon.

FORECAST POSITIONS AND MAX WINDS

INIT 21/0300Z 13.4N 46.6W 70 KT 80 MPH
12H 21/1200Z 14.0N 47.9W 75 KT 85 MPH
24H 22/0000Z 14.7N 49.8W 75 KT 85 MPH
36H 22/1200Z 15.2N 51.9W 70 KT 80 MPH
48H 23/0000Z 15.6N 54.2W 60 KT 70 MPH
72H 24/0000Z 16.5N 59.3W 55 KT 65 MPH
96H 25/0000Z 17.5N 64.5W 50 KT 60 MPH
120H 26/0000Z 18.0N 69.5W 45 KT 50 MPH

$$
Forecaster Berg

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I thought we'd see a change at update but I guess not. Danny looks about as good as it ever has. We'll see what the morning brings. It'll be good to get recon and research flights out there.

I have a feeling because he is so small and looking good winds in the eye wall are higher then what's stated. The change in pressure is huge over such a small area. Tracy hit Darwin Australia with a compact area of very intense winds. This is kind of the opposite of Sandy which had a huge area of similar strength winds

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I have a feeling because he is so small and looking good winds in the eye wall are higher then what's stated. The change in pressure is huge over such a small area. Tracy hit Darwin Australia with a compact area of very intense winds. This is kind of the opposite of Sandy which had a huge area of similar strength winds

 

Yeah, I think it's stronger than a cat 1.

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Very impressive looking cane despite small stature.  Will see how much he atrophies hitting the dry air / shear coming up.  Bigger issue imho is whether he can steer clear to north of the PR and DR.  Could be interesting to see what he can become if he can hold on for that bath water approaching the Turks and Caicos.  

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