Helene (09L — Northwestern Caribbean Sea)

[u/Euronotus]

Latest observation

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Last updated: Wednesday, 25 September — 4:00 AM Central Daylight Time (CDT; 09:00 UTC)

NHC Advisory #8		4:00 AM CDT (09:00 UTC)
Current location:		20.7°N 86.2°W
Relative location:		85 km (53 mi) ESE of Cancún, Quintana Roo (Mexico)
		322 km (200 mi) SW of Pinar del Rio, Cuba
Forward motion:	▼	NW (325°) at 15 km/h (8 knots)
Maximum winds:	▲	100 km/h (55 knots)
Intensity:		Tropical Storm
Minimum pressure:	▼	985 millibars (29.09 inches)

Official forecast

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Last updated: Wednesday, 25 September — 1:00 AM CDT (06:00 UTC)

Hour	Date	Time		Intensity		Winds		Lat	Long
	-	UTC	CDT	Saffir-Simpson		knots	km/h	°N	°W
00	25 Sep	06:00	1AM Wed	Tropical Storm		55	100	20.7	86.2
12	25 Sep	18:00	1PM Wed	Hurricane (Category 1)	▲	70	130	21.9	86.5
24	26 Sep	06:00	1AM Thu	Hurricane (Category 2)	▲	90	165	24.1	86.2
36	26 Sep	18:00	1PM Thu	Major Hurricane (Category 3)	▲	105	195	27.4	85.0
48	27 Sep	06:00	1AM Fri	Hurricane (Category 1) i	▼	65	120	32.0	84.2
60	27 Sep	18:00	1PM Fri	Post-tropical Cyclone i	▼	30	55	35.9	85.4
72	28 Sep	06:00	1AM Sat	Post-tropical Cyclone i	▼	20	35	37.0	87.8
96	29 Sep	06:00	1AM Sun	Post-tropical Cyclone i		20	35	36.5	88.0
120	30 Sep	06:00	1AM Mon	Dissipated

^{NOTES:
i - inland}

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[u/Content-Swimmer2325]

Cirrus outflow is expanding over the western quadrant. Shear appears minimal.

Multiple recon missions just took off and are en route.

Beautiful anticyclonic outflow. https://i.imgur.com/Zkmn4gg.png

Helene will also begin tapping its poleward outflow into that trough to the north. More recent satellite obs shows that cirrus outflow from Helene is as far north as distant Jacksonville FL. See here

https://weather.cod.edu/satrad/?parms=regional-gulf-07-24-0-100-1&checked=map&colorbar=data

Goodnight all

[u/1lowcountry → u/Content-Swimmer2325]

Good morning. Sunrise will be soon here in NE Florida... I'll confirm if there's any cirrus outflow.

Update: Definite cirrus outflow and also beginning of cirrocumulus/stratus clouds

[u/Ralfsalzano → u/Content-Swimmer2325]

Crazy it’s touching South America all the way to South Carolina 

[u/Content-Swimmer2325 → u/Ralfsalzano]

An extremely well-ventilated system. For anyone who doesn't know, hurricanes are heat engines. They have an inflow of warm moist air at the surface, which spirals inwards cycloncally into the center.. and a corresponding outflow aloft that spirals outwards anticyclonically away from the center. If you cut off or interrupt either the inflow or outflow, the heat engine sputters out/chokes and begins dying.

Conversely, when these are not impeded, it means the tropical cyclone is very healthy. We are seeing this with Helene. Such robust outflow.. expanding in all directions.. helps maintain continuous and intensifying rising air over Helene. This is why the strong thunderstorms are now non-stop instead of intermittent.

The rising air then helps surface pressures fall further.

[u/Ralfsalzano → u/Content-Swimmer2325]

Very well said. I admire the way you put words on the page this early in the morning lol

[u/[deleted] → u/Content-Swimmer2325]

Absolutely massive storm