ATL: ISAAC - Post-Tropical - Discussion

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Re: ATL: ISAAC - Tropical Depression - Discussion

#721 Postby AutoPenalti » Fri Sep 14, 2018 3:35 pm

LLC is really weak. It's pooping out convection that doesn't seem to have that swirl to it.
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Re: ATL: ISAAC - Tropical Depression - Discussion

#722 Postby Buck » Fri Sep 14, 2018 3:41 pm

Yeah, no wonder models are everywhere/nowhere with this... it's practically nothing at the moment and anything can happen in the Western Caribbean down the road. Not gonna be surprised if a 2.0 happens.
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Re: ATL: ISAAC - Tropical Depression - Discussion

#723 Postby AutoPenalti » Fri Sep 14, 2018 3:51 pm

Although, if my eyes aren't playing tricks on me, the last few frames seem to show some sort of banding occuring near the center.

Image
Image
Last edited by AutoPenalti on Fri Sep 14, 2018 3:55 pm, edited 1 time in total.
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Re: ATL: ISAAC - Advisories

#724 Postby cycloneye » Fri Sep 14, 2018 3:52 pm

BULLETIN
Tropical Storm Isaac Advisory Number 29
NWS National Hurricane Center Miami FL AL092018
500 PM AST Fri Sep 14 2018

...ISAAC BECOMES A TROPICAL STORM AGAIN BUT ITS FUTURE IS UNCLEAR...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...15.3N 68.2W
ABOUT 250 MI...400 KM SSE OF SANTO DOMINGO DOMINICAN REPUBLIC
ABOUT 600 MI...965 KM ESE OF KINGSTON JAMAICA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.

Interests in Jamaica should monitor the progress of Isaac.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Tropical Storm Isaac was
located near latitude 15.3 North, longitude 68.2 West. Isaac is
moving toward the west near 14 mph (22 km/h), and this general
motion with some decrease in forward speed is anticipated over the
next couple of days with a turn to the west-northwest possible by
late Sunday. On the forecast track, Isaac will move over the
eastern and central Caribbean Sea during the next few days, and be
near or south of Jamaica early next week.

NOAA Hurricane Hunter data indicate that maximum sustained winds
have increased to near 40 mph (65 km/h) with higher gusts.
Little change in strength is forecast during the next 36 hours.
Isaac is forecast to become a tropical depression on Sunday and
degenerate into a wave on Monday. However this is an uncertain
prediction.

Tropical-storm-force winds extend outward up to 45 miles (75 km)
from the center.

The estimated minimum central pressure from dropsonde data is 1002
mb (29.59 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL: Isaac is expected to produce additional rainfall of 2 to
3 inches with isolated maximum totals of up to 5 inches across
southeast Puerto Rico. Rainfall totals of 1 to 2 inches with
maximum amounts of 3 inches are possible across the remainder of
Puerto Rico, the Virgin Islands, the Leeward Islands and the
northern Windward Islands. Rainfall totals of 2 to 3 inches with
isolated maximum amounts of 4 inches are possible across the south-
central portion of the Dominican Republic, southwest Haiti and most
of Jamaica except for the eastern portion of Jamaica where rainfall
totals of 2 to 4 inches and maximum amounts of 6 inches are
possible. This rainfall may cause life-threatening flash floods.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Blake



Tropical Storm Isaac Discussion Number 29
NWS National Hurricane Center Miami FL AL092018
500 PM AST Fri Sep 14 2018

It has been a very interesting flight of the NOAA Hurricane Hunter
aircraft this afternoon. Dropsonde and SFMR data indicate that the
maximum winds are around 35 kt again, and the pressure has fallen
to about 1002 mb. However, the system is tilted southward with
vertical height due to northerly shear, and scatterometer and
Hurricane Hunter tail-Doppler radar data indicate the system is
elongated from northeast to southwest, albeit closed. Note that the
plane was unable to sample the southwestern quadrant well because of
strong convection and intense lightning, so the flight-level winds
showing no circulation were unrepresentative.

The intensity forecast hasn't gotten any easier with Isaac.
Vertical shear is expected to decrease a bit more, which might
diminish the effects of dry air seen on water vapor images around
the cyclone. However, the GFS and ECMWF continue to insist that
Isaac will degenerate into a wave within the next 2 or 3 days, which
is almost unanimously supported by their respective ensemble
members. This is the solution that the official forecast follows.
It should be noted that none of the global models show pressures
this low now with Isaac, except the UKMET, and that model is the one
that holds onto the circulation the longest. The reality of the
situation is that the long-term future of Isaac is cloudy, and the
best advice is just to follow NHC advisories every 6 hours to see
if we gain any confidence.

Isaac is moving westward at about 12 kt. A ridge over the
southwestern Atlantic should steer the cyclone westward over the
weekend then west-northwestward early next week as Isaac reaches a
weaker portion of the ridge. Just like yesterday, a stronger system
would likely turn more to the west-northwest earlier, moving
closer to Jamaica. Since the system is forecast to be weaker, the
forecast lies on the westward and faster side of the guidance, and
should also be considered low confidence since it depends on the
intensity. Interests in Jamaica should monitor the progress of the
Isaac.


FORECAST POSITIONS AND MAX WINDS

INIT 14/2100Z 15.3N 68.2W 35 KT 40 MPH
12H 15/0600Z 15.4N 70.1W 35 KT 40 MPH
24H 15/1800Z 15.4N 72.2W 35 KT 40 MPH
36H 16/0600Z 15.7N 74.2W 35 KT 40 MPH
48H 16/1800Z 16.2N 76.3W 30 KT 35 MPH
72H 17/1800Z 17.5N 80.0W 25 KT 30 MPH
96H 18/1800Z...DISSIPATED

$$
Forecaster Blake
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Re: ATL: ISAAC - Tropical Storm - Discussion

#725 Postby cycloneye » Fri Sep 14, 2018 3:54 pm

...ISAAC BECOMES A TROPICAL STORM AGAIN BUT ITS FUTURE IS UNCLEAR...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...15.3N 68.2W
ABOUT 250 MI...400 KM SSE OF SANTO DOMINGO DOMINICAN REPUBLIC
ABOUT 600 MI...965 KM ESE OF KINGSTON JAMAICA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES
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Re: ATL: ISAAC - Tropical Storm - Discussion

#726 Postby meriland29 » Fri Sep 14, 2018 3:59 pm

What? A TS again after so close to looking like a wave as of recent. ...well Ill be dipped...
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Re: ATL: ISAAC - Tropical Storm - Discussion

#727 Postby HurricaneBelle » Fri Sep 14, 2018 4:00 pm

...ISAAC BECOMES A TROPICAL STORM AGAIN BUT ITS FUTURE IS UNCLEAR...


He's just like the rest of us.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#728 Postby jlauderdal » Fri Sep 14, 2018 4:07 pm

isaac had a good day, he is cheating death...the models have had a hard time completely killing off the energy so not a huge surprise he still has a shot
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Re: ATL: ISAAC - Tropical Depression - Discussion

#729 Postby AnnularCane » Fri Sep 14, 2018 4:11 pm

Craters wrote:
SoupBone wrote:
meriland29 wrote:He's the little engine that could(n't). He's trying to desperately cling to life by firing convection, but he's still moving at 16mph. He's not dead (yet), Jim.


Or, converesly, Isaac speaking for himself: "I'm not dead yet! I don't want to go on the cart!"

(https://www.youtube.com/watch?v=UPatfgoNBRo)



Guess he was right. :lol:
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Re: ATL: ISAAC - Tropical Storm - Discussion

#730 Postby HurricaneBelle » Fri Sep 14, 2018 4:12 pm

I love this comment from the discussion, which is basically NHC's way of saying ¯\_(ツ)_/¯

The reality of the situation is that the long-term future of Isaac is cloudy, and the best advice is just to follow NHC advisories every 6 hours to see if we gain any confidence.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#731 Postby EquusStorm » Fri Sep 14, 2018 4:12 pm

Its appearance with persistent convection for over 24 hours and redeveloping banding is very impressive; not surprised it's easily at tropical storm intensity again but just wondered if the LLC was closed. If it stays closed it might well hang on decently well, but it's gonna need to slow down a little to stay closed
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...but still, though, a lot more interesting than the 2013 season.

Not a meteorologist, in fact more of an idiot than anything. You should probably check with the NHC or a local NWS office for official information.

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Re: ATL: ISAAC - Tropical Storm - Discussion

#732 Postby blp » Fri Sep 14, 2018 4:13 pm

Very interesting snippet of discussion by the NHC on the intensity. Its going to be interesting how this evolves. I don't feel so bad because looks like they can't figure out either why the models dissipate this.

The intensity forecast hasn't gotten any easier with Isaac.
Vertical shear is expected to decrease a bit more, which might
diminish the effects of dry air seen on water vapor images around
the cyclone. However, the GFS and ECMWF continue to insist that
Isaac will degenerate into a wave within the next 2 or 3 days, which
is almost unanimously supported by their respective ensemble
members.
This is the solution that the official forecast follows.
It should be noted that none of the global models show pressures
this low now with Isaac, except the UKMET, and that model is the one
that holds onto the circulation the longest. The reality of the
situation is that the long-term future of Isaac is cloudy, and the
best advice is just to follow NHC advisories every 6 hours to see
if we gain any confidence.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#733 Postby Tampa Bay Hurricane » Fri Sep 14, 2018 4:15 pm

Thank you AutoPenalti for posting! Isaac might be trying to wrap up in that image. Going to need to watch it. Euro shows a trough at 120 hours causing Isaac to cross Cuba and get into the Gulf of Mexico. Then it shows a ridge building which would push Isaac NW. The GOM and Caribbean islands need to watch it.
https://photos.app.goo.gl/KR3yvzexEZKaWuCdA
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Re: ATL: ISAAC - Tropical Storm - Discussion

#734 Postby Sciencerocks » Fri Sep 14, 2018 4:16 pm

LOL,

They upgraded to it to a tropical storm and found it closed. It looks the best it has looked since 50 west.

No longer being sheared
Moving into a more favorable environment
Ship, LGEM, and TVCN all show strengthening...The main intensity models on that chart.

I wouldn't stop watching this.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#735 Postby AutoPenalti » Fri Sep 14, 2018 4:20 pm

Just a hunch, but GFS and Euro may not be taking into account the possible reformation of the LLC to it's South. Maybe by the next run we see some adjustments?
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Re: ATL: ISAAC - Tropical Storm - Discussion

#736 Postby Hurricane Andrew » Fri Sep 14, 2018 4:26 pm

18z SHIPS guidance text, for reference...

Code: Select all

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    35    39    42    45    48    53    57    64    68    73    78    83    90
V (KT) LAND       35    39    42    45    48    53    57    64    68    73    78    83    90
V (KT) LGEM       35    38    40    43    46    52    59    68    77   DIS   DIS   DIS   DIS
Storm Type      TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP   N/A   N/A   N/A   N/A

SHEAR (KT)        13     7     7     9    10     4    11     7     9   N/A   N/A   N/A   N/A
SHEAR ADJ (KT)     7     3     2     4     7     4     4     0     3   N/A   N/A   N/A   N/A
SHEAR DIR         25    37    38    41    63    32    19   351   353   N/A   N/A   N/A   N/A
SST (C)         28.7  28.8  28.9  28.8  28.7  28.7  29.1  29.5  29.6   N/A   N/A   N/A   N/A
POT. INT. (KT)   148   149   150   149   147   147   154   161   162   N/A   N/A   N/A   N/A
ADJ. POT. INT.   146   147   146   144   141   141   149   155   157   N/A   N/A   N/A   N/A
200 MB T (C)   -53.4 -53.2 -53.3 -53.4 -53.0 -53.1 -53.0 -53.3 -53.5   N/A   N/A   N/A   N/A
200 MB VXT (C)  -0.2   0.0  -0.1   0.1   0.2   0.2   0.5   0.4   0.2  N/A   N/A   N/A   N/A
TH_E DEV (C)      13    13    12    12    12    11    12    11    11   N/A   N/A   N/A   N/A
700-500 MB RH     48    50    49    52    54    57    56    60    64   N/A   N/A   N/A   N/A
MODEL VTX (KT)    11    10     9     9     8     7     5     5     5  LOST  LOST  LOST  LOST
850 MB ENV VOR    38    40    41    45    46    49    29    28     8   N/A   N/A   N/A   N/A
200 MB DIV        11     0    13    23    11    24     4     5     0   N/A   N/A   N/A   N/A
700-850 TADV       0     1     1     0     0     4     0     0    -1   N/A   N/A   N/A   N/A
LAND (KM)        301   306   281   240   248   258   167   109   229   N/A   N/A   N/A   N/A
LAT (DEG N)     15.3  15.4  15.4  15.5  15.5  15.7  16.3  17.0  17.7   N/A   N/A   N/A   N/A
LONG(DEG W)     67.6  68.9  70.1  71.1  72.2  74.1  76.2  78.3  80.4   N/A   N/A   N/A   N/A
STM SPEED (KT)    13    12    11    10    10    10    11    11    11   N/A   N/A   N/A   N/A
HEAT CONTENT      56    58    64    66    66    89    50    76    64  9999  9999  9999  9999


Ignore the weird "N/A"s, etc, as the LGEM's "DIS" after 72 hours makes no sense to me.

FWIW, both SHIPS and LGEM intensity models bump this to a hurricane. For me, all depends on what that shear does in the western part of the Caribbean.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#737 Postby RL3AO » Fri Sep 14, 2018 4:34 pm

HurricaneBelle wrote:I love this comment from the discussion, which is basically NHC's way of saying ¯\_(ツ)_/¯

The reality of the situation is that the long-term future of Isaac is cloudy, and the best advice is just to follow NHC advisories every 6 hours to see if we gain any confidence.


I was trying to guess who wrote that before looking at the name. I went with Lix, but I can totally see that being Eric Blake. He'll have more zingers in the future I think.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#738 Postby Tampa Bay Hurricane » Fri Sep 14, 2018 4:49 pm

https://www.tropicaltidbits.com/sat/sat ... roduct=vis
On high resolution imagery it appears that there is some spin and banding near the center but it’s being pushed quickly. It’s speed may be slowing as you get the typical trade wind piling in the western Caribbean.
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Re: ATL: ISAAC - Tropical Storm - Discussion

#739 Postby meriland29 » Fri Sep 14, 2018 5:11 pm

Of he ends up surviving the dead zone and gets into the Gulf (and that's a big if)...what are the conditions supposed to be like there by the time he would get there in terms of sheer, water temps, etc?
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Re: ATL: ISAAC - Tropical Storm - Discussion

#740 Postby Socalhurcnegirl227 » Fri Sep 14, 2018 5:20 pm

jlauderdal wrote:isaac had a good day, he is cheating death...the models have had a hard time completely killing off the energy so not a huge surprise he still has a shot

hes tryin to live his best life on his caribbean cruise :lol:
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