ATL: HERMINE - Post-Tropical - Discussion

[TheStormExpert]

Down to 20%/50% with marginally favorable conditions only expected @ 8am TWO.

Disorganized showers a few thunderstorms associated with a tropical
wave are located about 1150 miles east of the Lesser Antilles.
Environmental conditions are forecast to be marginally conducive for
development during the next few days, and any development should be
slow to occur. This system is expected to move westward and then
west-northwestward at 15 to 20 mph across the tropical Atlantic
Ocean, through the eastern Caribbean Sea, and then near the Greater
Antilles.
* Formation chance through 48 hours...low...20 percent
* Formation chance through 5 days...medium...50 percent

[bvigal]

Precip water view of 99L
(This picture will be overwritten tomorrow morning, I no longer keep a photo storage site)

[MGC]

99L don't look like much this morning. Just a few scattered convective cells. Miles and miles of dry air DEAD ahead of 99L will limit its development chances....perhaps conditions will improve in the Western Atlantic.....MGC

[NDG]

99L is still trapped close to the SAL this morning. The GFS messed up on Friday, really missed the dry environment that 99L was going to encounter. 90L is within a moist environment thus why it has a better chance of development in the short range.

[Ntxw]

Needless to say it needs convection if it's going to do anything.

[gatorcane]

Bear in mind the NHC 50% chance of development does not reflect development chances if 99l makes it to near the Bahamas where models suggest conditions could be more favorable for development.

[Blown Away]

http://rammb.cira.colostate.edu/product ... r=AL992016

Maybe the very early makings of a LLC??

[blp]

MIMIC TPW is still quite impressive. This is not going away anytime soon despite not showing much convection.

http://tropic.ssec.wisc.edu/real-time/m ... /main.html

[gatorcane]

Lacking convection at the moment but overall cyclonic spin quite apparent and a good signature as blp pointed out

[SFLcane]

Sorry folks this isn't going to develop in the term likely never at all. There is your reason why convection goes poof. It's been part of the problem last what few years if not more. Development chances 50% in 5 days? I'd say more like 20% the way I see it.

http://weather.msfc.nasa.gov/GOES/GOES1 ... 3i5hRP.jpg

[cycloneye]

For Tuesday Afternoon the first plane to investigate 99L but if Necesarry.

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1100 AM EDT SUN 21 AUGUST 2016
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 22/1100Z TO 23/1100Z AUGUST 2016
TCPOD NUMBER.....16-087

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW-LEVEL INVEST MISSION
INTO SYSTEM APPROACHING LESSER ANTILLES NEAR 15.0N 58.0W FOR
23/1800Z. BEGIN 6-HRLY FIXES AT 24/0600Z IF SYSTEM DEVELOPS

[SFLcane]

This will more then likely will be cancelled. No need to waste fuel on patch of clouds.

[cycloneye]

This will more then likely will be cancelled. No need to waste fuel on patch of clouds.

Unless there are more than popcorn type clouds.

[rockyman]

MIMIC shows an absolutely huge system. In general, the larger the circulation, the longer it takes to get going. Part of the circulation envelope will be scraping Hispaniola, but the size of the system will make it more likely to avoid a total "poof".

Also, as Fiona pulls away to the north, 99L should no longer have to "share" the moisture feed from the ITCZ with another system.

http://tropic.ssec.wisc.edu/real-time/m ... /main.html

[p1nheadlarry]

Lacking convection at the moment but overall cyclonic spin quite apparent and a good signature as blp pointed out

https://s10.postimg.org/xf9otddvd/vis_lalo_animated.gif

Looks like the coc is closer to 14 than 13 north on that pic

[wxman57]

I'd feel more comfortable going for development if the global models showed some support. The Mimic-TPW loop is quite impressive, though, and a number of GFS, EC, and CMC ensembles support development. I don't expect any significant change in status until it passes the NE Caribbean Wed/Thu.

[psyclone]

its best opportunity for development may still reside just beyond the 5 day forecast window. Nevertheless, it will need some persistent convection at some point. But it's a big circulation destined to encounter warmer waters in late August. I wouldn't write it off but it's likely a snooze fest for the next few days.

[NDG]

its best opportunity for development may still reside just beyond the 5 day forecast window. Nevertheless, it will need some persistent convection at some point. But it's a big circulation destined to encounter warmer waters in late August. I wouldn't write it off but it's likely a snooze fest for the next few days.

Warmers might help in instability but it still needs to get away from the capped atmosphere over it, may do that as it starts nearing the Leeward Islands, but there's still a lot of dry air over the Caribbean.

Is over a fairly stable environment right now:

Code: Select all

ate: 6 hour UKMET valid 18Z SUN 21 AUG 16
Station: 15,-45
Latitude:   15.00
Longitude: -45.00
-------------------------------------------------------------------------------
LEV PRES  HGHT  TEMP  DEWP  RH  DD   WETB DIR SPD THETA THE-V THE-W THE-E   W
     mb     m     C     C    %   C     C  deg knt   K     K     K     K    g/kg
-------------------------------------------------------------------------------
  0  850  1521  18.1  16.9  93  1.2  17.3  99  20 305.1 307.8 296.3 348.2 14.43
  1  700  3167  10.6   8.2  85  2.4   9.1  94  16 314.3 316.1 295.4 344.8  9.82
  2  600  4436   3.7  -0.4  75  4.0   1.5  83  11 320.4 321.6 294.4 340.4  6.22
  3  500  5899  -3.8 -13.4  47  9.6  -7.7  62   6 328.4 329.0 293.7 337.7  2.72
  4  400  7624 -15.0                       64   9 335.5                       
  5  300  9737 -30.2                       54  18 342.8                       
  6  250 11006 -40.4                       57  21 346.0                       
  7  200 12487 -52.8                       79  25 349.2                       
  8  150 14274 -68.8                       86  23 351.6                       
  9  100 16645 -76.4                      121  13 380.1                       
TRP                                             0                             
WND                                             0                             

Sounding variables and indices
Freezing level:          550.73 mb =  5157.07 m = 16919.31 ft
Wetbulb zero:            584.13 mb =  4651.44 m = 15260.44 ft
Precipitable water:        1.21 inches
700-500 lapse rate:        5.27 C/km
ThetaE index:            10347.21 C Layer  700.0-  -0.0 mb
Showalter Index:          -0.16 C Risk: Thunderstorms probable
Total Totals Index:       42.57 C Risk: None
  Vertical Totals Index:  21.86 C
  Cross Totals Index:     20.71 C
K Index:                  36.38   Risk: > 80 % chance of thunderstorms
Sweat Index:             247.80   Risk: None
Energy Index:             -2.06   Risk: Severe Thunderstorms probable


[gatorcane]

NHC to release outlook within the next 30 minutes. Models have become more bullish (all develop except the Euro which has yet to run) but a little bit outside of the NHC 5-day window when the system clears the islands. So perhaps NHC sticks with 50% for now would be my guess.

[cycloneye]

Mentions the Bahamas.

A tropical wave located about 1100 miles east of the Lesser Antilles
is producing disorganized showers and a few thunderstorms. The
proximity of this system to dry air is expected to inhibit
significant development during the next few days while the
disturbance moves westward to west-northwestward at 15 to 20 mph.
Environmental conditions could become more conducive for development
late this week when the system is expected to be near Hispaniola and
the southeastern Bahamas.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...medium...40 percent