ATL: IRMA - Post-Tropical - Discussion

[Alyono]

I have to disagree with the NHC in the strongest possible terms about this striking as a category 3 and not a category 4 hurricane. One cannot ignore the signal from the global models or the pressure falls we have seen. I strongly believe this will be a 4 or maybe even a 5 at landfall

[JaxGator]

What wind shear are you guys talking about, I haven't heard one of the pros on TV mention Wind Shear, all they are talking about how the cool front north is just venting this storm and making her very large.

The low that's centered over the northern gulf and pushing se.. it's what is eroding the ridge and allowing Irma to turn north.. might help ventilation in the short term, but will eventually wreak havoc on Irma..

40kt of shear over the peninsula could save some lives.

I think its mostly Irma's outflow causing that. It's huge.

[AdamFirst]

Irma has stuttered near the north coast of Cuba for the past few
hours, which may be a harbinger of the north-northwestward turn
that we've been waiting for. In any event, Irma appears to be
moving very slowly toward the northwest, or 305/5 kt, very gradually
shifting away from the north coast of Cuba. With the hurricane
located near a break in the subtropical ridge, it should turn
north-northwestward soon and accelerate near or along the west
coast of Florida during the next 36-48 hours. Because of Irma's
hesitation to move northwestward, the new track guidance has shifted
ever so slightly westward, and the new NHC track is just a little
left of the previous one. Although it is likely that the eye will
move near or over the Lower Keys Sunday morning, the hurricane's
angle of approach to the west coast of Florida makes it very
difficult to pinpoint exactly where Irma will cross the Florida Gulf
coast.

If an eyewall replacement occurs within the next 6-12 hours, Irma
has an opportunity to restrengthen a bit while it moves across the
Straits of Florida. After that time, however, southwesterly shear
is expected to increase to 25-30 kt in about 24 hours and then
continue increasing through 48 hours. This shear, in addition to
Irma's core interacting with Florida, is likely to cause a
weakening trend after 24 hours. The new intensity guidance calls
for an adjustment from the previous forecast, although it
conservatively lies near the upper bound of the reliable models.
Irma is still expected to approach the Florida Keys and Florida
west coast as a major hurricane, and combined with its large size,
will produce significant storm surge flooding in those areas.

[eastcoastFL]

FPL reporting about 230k power outages so far. Gonna be a lot more as the next 2-3 days go by.

[MrJames]

11PM shifting west

Irma's nearly 24-hour traversal of the north coast of Cuba appears
to have affected the hurricane's structure and intensity. An
earlier NOAA Hurricane Hunter aircraft and a more recent Air Force
reconnaissance flight both measured maximum flight-level winds near
105 kt and surface winds near 95 kt. The planes have reported
a double eyewall structure, which has also been observed in WSR-88D
Doppler radar data from Miami and Key West. Irma's intensity has
been conservatively lowered to 105 kt, and I'd rather wait to lower
the winds further until we've seen the full data set from the Air
Force mission.

Irma has stuttered near the north coast of Cuba for the past few
hours, which may be a harbinger of the north-northwestward turn
that we've been waiting for. In any event, Irma appears to be
moving very slowly toward the northwest, or 305/5 kt, very gradually
shifting away from the north coast of Cuba. With the hurricane
located near a break in the subtropical ridge, it should turn
north-northwestward soon and accelerate near or along the west
coast of Florida during the next 36-48 hours. Because of Irma's
hesitation to move northwestward, the new track guidance has shifted
ever so slightly westward, and the new NHC track is just a little
left of the previous one. Although it is likely that the eye will
move near or over the Lower Keys Sunday morning, the hurricane's
angle of approach to the west coast of Florida makes it very
difficult to pinpoint exactly where Irma will cross the Florida Gulf
coast.

If an eyewall replacement occurs within the next 6-12 hours, Irma
has an opportunity to restrengthen a bit while it moves across the
Straits of Florida. After that time, however, southwesterly shear
is expected to increase to 25-30 kt in about 24 hours and then
continue increasing through 48 hours. This shear, in addition to
Irma's core interacting with Florida, is likely to cause a
weakening trend after 24 hours. The new intensity guidance calls
for an adjustment from the previous forecast, although it
conservatively lies near the upper bound of the reliable models.
Irma is still expected to approach the Florida Keys and Florida
west coast as a major hurricane, and combined with its large size,
will produce significant storm surge flooding in those areas.

[eastcoastFL]

The low that's centered over the northern gulf and pushing se.. it's what is eroding the ridge and allowing Irma to turn north.. might help ventilation in the short term, but will eventually wreak havoc on Irma..

40kt of shear over the peninsula could save some lives.

I think its mostly Irma's outflow causing that. It's huge.

Wow you're probably right. I never even considered that.

[meriland29]

As per nhc..


000
WTNT41 KNHC 100258
TCDAT1

Hurricane Irma Discussion Number 44
NWS National Hurricane Center Miami FL AL112017
1100 PM EDT Sat Sep 09 2017

Irma's nearly 24-hour traversal of the north coast of Cuba appears
to have affected the hurricane's structure and intensity. An
earlier NOAA Hurricane Hunter aircraft and a more recent Air Force
reconnaissance flight both measured maximum flight-level winds near
105 kt and surface winds near 95 kt. The planes have reported
a double eyewall structure, which has also been observed in WSR-88D
Doppler radar data from Miami and Key West. Irma's intensity has
been conservatively lowered to 105 kt, and I'd rather wait to lower
the winds further until we've seen the full data set from the Air
Force mission.

Irma has stuttered near the north coast of Cuba for the past few
hours, which may be a harbinger of the north-northwestward turn
that we've been waiting for. In any event, Irma appears to be
moving very slowly toward the northwest, or 305/5 kt, very gradually
shifting away from the north coast of Cuba. With the hurricane
located near a break in the subtropical ridge, it should turn
north-northwestward soon and accelerate near or along the west
coast of Florida during the next 36-48 hours. Because of Irma's
hesitation to move northwestward, the new track guidance has shifted
ever so slightly westward, and the new NHC track is just a little
left of the previous one. Although it is likely that the eye will
move near or over the Lower Keys Sunday morning, the hurricane's
angle of approach to the west coast of Florida makes it very
difficult to pinpoint exactly where Irma will cross the Florida Gulf
coast.

If an eyewall replacement occurs within the next 6-12 hours, Irma
has an opportunity to restrengthen a bit while it moves across the
Straits of Florida. After that time, however, southwesterly shear
is expected to increase to 25-30 kt in about 24 hours and then
continue increasing through 48 hours. This shear, in addition to
Irma's core interacting with Florida, is likely to cause a
weakening trend after 24 hours. The new intensity guidance calls
for an adjustment from the previous forecast, although it
conservatively lies near the upper bound of the reliable models.
Irma is still expected to approach the Florida Keys and Florida
west coast as a major hurricane, and combined with its large size,
will produce significant storm surge flooding in those areas.


KEY MESSAGES:

1. Irma is expected bring life-threatening wind and storm surge to
the Florida Keys and southwestern Florida as an extremely dangerous
major hurricane tonight through Sunday. Preparations in the Florida
Keys and southwest Florida should be complete since tropical-storm-
force winds are already affecting portions of the coast.

2. There is an imminent danger of life-threatening storm surge
flooding in portions of central and southern Florida, including the
Florida Keys, where a Storm Surge Warning is in effect. The threat
of catastrophic storm surge flooding is highest along the southwest
coast of Florida, where 10 to 15 feet of inundation above ground
level is expected. This is a life-threatening situation, and
everyone in these areas should immediately follow any evacuation
instructions from local officials.

3. Irma will bring life-threatening wind impacts to much of Florida
regardless of the exact track of the center. Wind hazards from Irma
are also expected to spread northward through much of Georgia
and portions of South Carolina and Alabama.

4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 10 to 20 inches, with isolated amounts
of between 20 and 25 inches, are expected over the Florida Keys, the
Florida peninsula, and southeast Georgia from Saturday through
Monday. Significant river flooding is possible in these areas. Early
next week Irma will also bring periods of heavy rain to much of the
southeast United States where an average of 2 to 6 inches is
forecast, with isolated higher amounts, from North and South
Carolina to Tennessee and eastern Alabama. This includes some
mountainous areas which are more prone to flash flooding. Residents
throughout the southeast states should remain aware of the flood
threat and stay tuned to forecasts and warnings.

FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 23.5N 81.0W 105 KT 120 MPH
12H 10/1200Z 24.7N 81.7W 110 KT 125 MPH
24H 11/0000Z 26.8N 82.4W 105 KT 120 MPH
36H 11/1200Z 29.5N 83.4W 80 KT 90 MPH...ON THE COAST
48H 12/0000Z 32.2N 85.0W 55 KT 65 MPH...INLAND
72H 13/0000Z 35.3N 89.0W 25 KT 30 MPH...POST-TROP/INLAND
96H 14/0000Z 37.0N 88.5W 20 KT 25 MPH...POST-TROP/INLAND
120H 15/0000Z...DISSIPATED

[lando]

Track now offshore west coast... crazy

[eastcoastFL]

I have to disagree with the NHC in the strongest possible terms about this striking as a category 3 and not a category 4 hurricane. One cannot ignore the signal from the global models or the pressure falls we have seen. I strongly believe this will be a 4 or maybe even a 5 at landfall

Wow that's a bold statement. I have no reason to disagree. I actually agree with you 100% but I'm not a pro...you are.

[ConvergenceZone]

11pm advisory only saying a cat 3 at landfall? I hope that verifies.

Hmmm probably because of increased shear? That would be my guess as to why they are only
Expecting landfall is a Cat 3. They did say though on tv that it would probably get to a Cat4 before the weakening to a Cat 3 begins

[meriland29]

Doesn't sound like the NHC thinks she is going to strengthen unless she completes another ERC..

[birddogsc]

Key West seems to have just lost power.

The Two Friends feed showed the lights going out.

[AutoPenalti]

Friend down in Coconut Creek says it's pretty quiet.

[ava_ati]

I have to disagree with the NHC in the strongest possible terms about this striking as a category 3 and not a category 4 hurricane. One cannot ignore the signal from the global models or the pressure falls we have seen. I strongly believe this will be a 4 or maybe even a 5 at landfall

No offense, but I hope you are wrong in the worst way. I am shocked by that forecast.the NHC not yours

[Alyono]

Doesn't sound like the NHC thinks she is going to strengthen unless she completes another ERC..

it completed already. Plus, the global models show the most intensification AFTER Key West. SHIPS/LGE are being given far too much weight. We saw this last year with Matthew in the Caribbean. You cannot use global models for precise intensity, but you can for the trends

[Sciencerocks]

000
URNT15 KNHC 100308
AF302 2911A IRMA HDOB 19 20170910
024730 2311N 08024W 6967 02930 9775 +111 +105 206069 071 054 001 00
024800 2310N 08022W 6963 02939 9785 +110 +101 206068 068 052 001 00
024830 2309N 08020W 6966 02942 9790 +110 +100 206067 068 052 001 03
024900 2309N 08019W 6967 02947 9798 +108 //// 205067 068 058 004 01
024930 2308N 08017W 6969 02949 9810 +101 //// 204071 074 077 002 01
025000 2308N 08015W 6970 02952 //// +093 //// 202070 073 074 005 05
025030 2308N 08013W 6967 02960 9821 +101 //// 203069 070 /// /// 05
025100 2307N 08011W 6964 02970 9825 +102 //// 200070 071 066 002 01
025130 2307N 08009W 6964 02974 9828 +100 //// 202069 071 051 006 01
025200 2306N 08007W 6965 02975 9826 +103 //// 206071 074 052 003 01
025230 2306N 08005W 6968 02974 //// +089 //// 207083 087 050 004 01
025300 2306N 08003W 6973 02969 //// +076 //// 197081 087 048 011 01
025330 2305N 08001W 6971 02977 //// +071 //// 191078 079 049 010 05
025400 2305N 07959W 6965 02984 //// +066 //// 191081 082 048 010 05
025430 2305N 07958W 6969 02988 //// +068 //// 192078 080 051 007 05
025500 2305N 07956W 6966 02995 //// +068 //// 192078 080 048 010 01
025530 2304N 07954W 6966 03000 //// +066 //// 191080 081 047 010 05
025600 2304N 07952W 6970 03000 9896 +076 //// 192080 081 050 007 01
025630 2304N 07950W 6967 03009 9893 +088 +086 193078 079 049 006 00
025700 2303N 07949W 6971 03008 9896 +089 +083 194078 078 050 006 03
$$
;

[galaxy401]

I'm getting news alerts that the Florida Keys now have hurricane force gusts.

[meriland29]

Doesn't sound like the NHC thinks she is going to strengthen unless she completes another ERC..

it completed already. Plus, the global models show the most intensification AFTER Key West. SHIPS/LGE are being given far too much weight. We saw this last year with Matthew in the Caribbean. You cannot use global models for precise intensity, but you can for the trends

Then why does the NHC confirm it still has a double eyewall structure?

[eastcoastFL]

Local radar here is getting into some deep reds and I can hear some intense thunder rumbling now and lightning just flashed. Winds are call at the moment though.

[TJRE]

https://goes.gsfc.nasa.gov/goescolor/go ... latest.jpg

"There is a principle which is a bar against all information, which is proof against all arguments, and which cannot fail to keep a man in everlasting ignorance—that principle is contempt prior to investigation."
Herbert Spencer