ATL: HERMINE - Post-Tropical - Discussion

[SeGaBob]

Convection is sustaining nicely...when is dmin?

[SFLcane]

Jeff masters.....https://www.wunderground.com/blog/JeffM ... commenttop

Heavy rains from 99L will be capable of causing flash flooding problems in the Lesser Antilles, Virgin Islands, and Puerto Rico, but wind damage should not be an issue, since 99L will likely be, at worst, a moderate-strength tropical storm with 55 mph winds once it leaves the islands. The 8 am EDT Monday run of the SHIPS model showed moderately favorable conditions for development through Thursday. Wind shear will be in the light to moderate range, 5 - 15 knots, and SSTs will increase from 27.5°C (82°F) to 29°C (84°F), accompanied by an increase in the total heat content of the ocean. Working against development of 99L will be the large size of the storm, dry air of the SAL, potential interaction with the land areas of Puerto Rico and Hispaniola, and large-scale sinking air over the tropical Atlantic imparted by an unfavorable phase of the Madden-Julian Oscillation (MJO). None of the Sunday morning (00Z) operational runs of our three reliable models for predicting tropical cyclone genesis--the European, GFS and UKMET models--showed development of 99L into a tropical depression or tropical storm over the next four days, though the UKMET model predicted it could be a tropical depression in the Bahamas in five days. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 99L 2-day and 5-day development odds of 20% and 50%, respectively. I think these odds are too low, and should be 30% and 60%, respectively. The Hurricane Hunters are scheduled to investigate 99L on Tuesday afternoon.

I am concerned about the storm’s potential impacts on the Bahamas and the U.S. beyond five days, when the storm will likely be near or just north of the central Bahamas. The models are predicting a more favorable environment for development then, and the storm will be moving quite slowly, potentially allowing for some very high rainfall totals in the Bahamas, and to a lesser extent, Haiti and the Dominican Republic. While the 00Z Monday runs of the GFS and European model ensemble forecast had fewer than 10% of their members predicting that 99L would eventually become a hurricane, the storm will likely spend at least three days over a region of ocean with SSTs that are near record-warm: 29 - 29.5°C (84 - 85°F). Warm waters extend to great depth, resulting in an unusually high total ocean heat content. With some models forecasting that wind shear will be in the light to moderate range early next week, we have the potential for 99L--which does have a large circulation--to rapidly intensify into a large hurricane. Hopefully, the unfavorable phase of the MJO will help to put the brakes on such a possibility.

[La Sirena]

I certainly hope they launch this recon Tuesday! It should help to clarify the models since they've been all over the place with 99L.

[abajan]

Convection is sustaining nicely...when is dmin?

Around 5 PM for systems at that latitude, I think.

[JaxGator]

Jeff masters.....https://www.wunderground.com/blog/JeffM ... commenttop

Heavy rains from 99L will be capable of causing flash flooding problems in the Lesser Antilles, Virgin Islands, and Puerto Rico, but wind damage should not be an issue, since 99L will likely be, at worst, a moderate-strength tropical storm with 55 mph winds once it leaves the islands. The 8 am EDT Monday run of the SHIPS model showed moderately favorable conditions for development through Thursday. Wind shear will be in the light to moderate range, 5 - 15 knots, and SSTs will increase from 27.5°C (82°F) to 29°C (84°F), accompanied by an increase in the total heat content of the ocean. Working against development of 99L will be the large size of the storm, dry air of the SAL, potential interaction with the land areas of Puerto Rico and Hispaniola, and large-scale sinking air over the tropical Atlantic imparted by an unfavorable phase of the Madden-Julian Oscillation (MJO). None of the Sunday morning (00Z) operational runs of our three reliable models for predicting tropical cyclone genesis--the European, GFS and UKMET models--showed development of 99L into a tropical depression or tropical storm over the next four days, though the UKMET model predicted it could be a tropical depression in the Bahamas in five days. In their 8 am EDT Monday Tropical Weather Outlook, NHC gave 99L 2-day and 5-day development odds of 20% and 50%, respectively. I think these odds are too low, and should be 30% and 60%, respectively. The Hurricane Hunters are scheduled to investigate 99L on Tuesday afternoon.

Iam concerned about the storm’s potential impacts on the Bahamas and the U.S. beyond five days, when the storm will likely be near or just north of the central Bahamas. The models are predicting a more favorable environment for development then, and the storm will be moving quite slowly, potentially allowing for some very high rainfall totals in the Bahamas, and to a lesser extent, Haiti and the Dominican Republic. While the 00Z Monday runs of the GFS and European model ensemble forecast had fewer than 10% of their members predicting that 99L would eventually become a hurricane, the storm will likely spend at least three days over a region of ocean with SSTs that are near record-warm: 29 - 29.5°C (84 - 85°F). Warm waters extend to great depth, resulting in an unusually high total ocean heat content. With some models forecasting that wind shear will be in the light to moderate range early next week, we have the potential for 99L--which does have a large circulation--to rapidly intensify into a large hurricane. Hopefully, the unfavorable phase of the MJO will help to put the brakes on such a possibility.

That's an ominous outlook (and wording) he has there. Hopefully it'll change. We don't want a storm of that magnitude here (nor do the other states) but at the same time, I don't know how long Florida's hurricane drought can last.

[Nimbus]

JM mentioned the large size of the circulation being an inhibiting factor which is likely true, but there already appears to be better organization at the low levels, perhaps even an early inflow organization.

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=15&lon=-50&info=vis&zoom=1&width=1000&height=800&quality=90&type=Animation&palette=ir1.pal&numframes=10&mapcolor=black

[LarryWx]

Jeff masters.....https://www.wunderground.com/blog/JeffM ... commenttop

Iam concerned about the storm’s potential impacts on the Bahamas and the U.S. beyond five days, when the storm will likely be near or just north of the central Bahamas. The models are predicting a more favorable environment for development then, and the storm will be moving quite slowly, potentially allowing for some very high rainfall totals in the Bahamas, and to a lesser extent, Haiti and the Dominican Republic. While the 00Z Monday runs of the GFS and European model ensemble forecast had fewer than 10% of their members predicting that 99L would eventually become a hurricane, the storm will likely spend at least three days over a region of ocean with SSTs that are near record-warm: 29 - 29.5°C (84 - 85°F). Warm waters extend to great depth, resulting in an unusually high total ocean heat content. With some models forecasting that wind shear will be in the light to moderate range early next week, we have the potential for 99L--which does have a large circulation--to rapidly intensify into a large hurricane. Hopefully, the unfavorable phase of the MJO will help to put the brakes on such a possibility.

Actually, a decent portion of the Bahamas has SST''s in the upper 80's (~31C), not just 84-85 if I'm not mistaken.

[Hurricaneman]

The center seems to be in the western blob of convection, if so this is more organized than many of the models have it

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the National Hurricane Center and National Weather Service

[gatorcane]

wide shot again. Some observations:

1. Convection is sustaining nicely and cyclonic rotation evident
2. Some SAL is heading towards Fiona which would help keep Fiona at check (along with the shear), a weaker Fiona has implications for 99l downstream
3. Look at the thin string of clouds from 99L connecting to 90l....pretty cool!

[gatorcane]

Staying at 50%

A tropical wave located about 750 miles east of the Lesser Antilles
is producing disorganized shower and thunderstorm activity. Nearby
dry air is expected to slow development during the next couple of
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 move
near Hispaniola and the southeastern and central Bahamas. An Air
Force Reserve Hurricane Hunter aircraft is scheduled to investigate
this system on Tuesday, if necessary. Interests in the Lesser
Antilles, the Virgin Islands, and Puerto Rico should monitor the
progress of this system.
* Formation chance through 48 hours...low...20 percent
* Formation chance through 5 days...medium...50 percent

[psyclone]

Worth keeping in mind that the NHC still gives this a 50% chance of doing nothing.

[TheStormExpert]

Clearly they are factoring in the GFS.

[LarryWx]

wide shot again. Some observations:

1. Convection is sustaining nicely and cyclonic rotation evident
2. Some SAL is heading towards Fiona which would help keep Fiona at check (along with the shear), a weaker Fiona has implications for 99l downstream
3. Look at the thin string of clouds from 99L connecting to 90l....pretty cool!

https://s10.postimg.org/6jghr16ux/vis_animated.gif

Regarding the above satellite loop:

1) 99L looks clearly north of where the 12Z GFS had it at hour 6 (near current time). The 12Z Euro just initialized and it is further north/closer to the true position of 99L imo.
2) Fiona actually has convection firing up near the center again though sheared. She is a fighter and is likely coming for FL although no model has it as a TC then.

[cycloneye]

Winds from the NW at bouy 41040.

http://www.ndbc.noaa.gov/station_page.php?station=41040

[tarheelprogrammer]

Winds from the NW at bouy 41040.

http://www.ndbc.noaa.gov/station_page.php?station=41040

So, a center is there?

[cycloneye]

Winds from the NW at bouy 41040.

http://www.ndbc.noaa.gov/station_page.php?station=41040

So, a center is there?

North of bouy. Location is 14.516 N 53.024 W (14°30'59" N 53°1'27" W)

[p1nheadlarry]

JM mentioned the large size of the circulation being an inhibiting factor which is likely true, but there already appears to be better organization at the low levels, perhaps even an early inflow organization.

http://weather.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20HURRICANE&lat=15&lon=-50&info=vis&zoom=1&width=1000&height=800&quality=90&type=Animation&palette=ir1.pal&numframes=10&mapcolor=black

For a large storm that's not exactly crawling out there, it could be a downside. Upside would be if it did develop by the time it reaches the islands, that's trouble.

[tarheelprogrammer]

Winds from the NW at bouy 41040.

http://www.ndbc.noaa.gov/station_page.php?station=41040

So, a center is there?

North of bouy. Location is 14.516 N 53.024 W (14°30'59" N 53°1'27" W)

Thanks

[Weatherboy1]

Updated WPC discussion alludes to ridging in the SE U.S. not in a hurry to go anywhere. That would tend to argue for steering whatever MAY be in the Bahamas toward the west, I would think ...

VALID 12Z THU AUG 25 2016 - 12Z MON AUG 29 2016

...PATTERN OVERVIEW...

SUBTROPICAL RIDGING WILL HOLD STRONG OVER THE SOUTHEASTERN U.S.
LATE THIS WEEK AND THROUGH THE WEEKEND...WHILE GENERAL TROUGHING
SHOULD PERSIST OVER THE WESTERN U.S.. AT THE SURFACE...A COLD
FRONT WILL PRESS THROUGH THE GREAT LAKES AND NORTHEAST
THURSDAY-FRIDAY BEFORE THE TAIL END OF THE BOUNDARY WEAKENS AND
STALLS ACROSS THE SOUTHEAST AND TENNESSEE VALLEY THIS WEEKEND.
OTHER SURFACE BOUNDARIES COULD POTENTIALLY CROSS THE NORTH CENTRAL
U.S. THIS WEEKEND AND INTO EARLY NEXT WEEK...BUT THE DETAILS OF
THESE FEATURES AND THE SHORTWAVE ENERGY MOVING THROUGH ALOFT
REMAIN VERY UNCERTAIN.

[Aric Dunn]

Winds from the NW at bouy 41040.

http://www.ndbc.noaa.gov/station_page.php?station=41040

people keep posting this. the bouy is not close enough to give us any information pertaining the llc except maybe general falling pressures... the wind field is large but diffuse at the moment.. . Its too far away.

the bouy (red dot) and the overall center being well to the north.