ATL: IRMA - Post-Tropical - Discussion

[rickybobby]

Just arrived at mellow mushroom and they have it on the weather channel. They showed a few models going to Louisiana now.

[syfr]

Avila's observations are well organized and informative. Ive always appreciated his work.

[fwbbreeze]

on the power outage map...I wonder how they came up with Bay county in the Florida Panhandle with a 20-30% chance of outages.....and nothing for Walton county just to its west. I get all the other percentages pretty well.

[tolakram]

First time we've seen a strengthening indication on their discussion.

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM

Hurricane Irma Discussion Number 39
NWS National Hurricane Center Miami FL AL112017
500 PM EDT Fri Sep 08 2017

Latest data from an Air Force Hurricane Hunter plane a few hours ago
indicate that Irma's intensity continues to fluctuate, and the
winds are estimated at 135 kt. The last minimum central pressure
was 925 mb. Another reconnaissance plane will check Irma soon.

The environment is favorable for Irma to maintain its category 4
status, and only unpredictable eyewall replacement cycles could
result in intensity fluctuations during the next 48 hours. The
interaction of the hurricane's circulation with Cuba will probably
not result in any relevant change in intensity. In summary, the NHC
forecast brings Irma near south Florida as a category 4 hurricane.
After landfall, interaction with land and an increase in wind shear
should induce gradual weakening.

Satellite images and radar fixes from Cuba indicate that Irma has
slowed down and is now moving toward the west or 280 degrees at
about 10 kt. The hurricane should continue on this track for the
next 12 hours to 24 hours, and this track will bring the core of
Irma very close to the north coast of Cuba. After that time, Irma
should reach the southwestern edge of the subtropical high and begin
to move toward the northwest and north-northwest toward the Florida
peninsula. The precise moment of this turn is still uncertain, and
that is why NHC emphasizes that nobody should focus on the exact
track of the center. This afternoon's NHC forecast was again
adjusted a little bit westward following the trend of the ECMWF
model and both the HFIP corrected consensus and the FSU
Superensemble. In fact, these 3 aids continued to be tightly packed.

KEY MESSAGES:

1. Irma will continue to bring life-threatening wind, storm surge,
and rainfall hazards to portions of the Bahamas and the north coast
of Cuba, especially over the adjacent Cuban Keys, through Saturday.

2. Irma is expected to make landfall in Florida as an extremely
dangerous major hurricane, and will bring life-threatening wind
impacts to much of the state regardless of the exact track of the
center.

3. There is the danger of life-threatening storm surge inundation in
southern Florida and the Florida Keys during the next 36 hours,
where a Storm Surge Warning is in effect. The threat of significant
storm surge flooding along the southwest coast of Florida has
increased, and 8 to 12 feet of inundation above ground level is
possible in this area. This is a life-threatening situation.
Everyone in these areas should take all actions to protect life and
property from rising water and follow evacuation instructions from
local officials.

4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 8 to 15 inches, with isolated amounts of
20 inches are expected over the Florida Keys and much of the Florida
peninsula through Tuesday night. The highest amounts are expected
over the eastern Florida peninsula and upper Florida Keys. Irma
will likely bring periods of heavy rain to much of Georgia, South
Carolina, and western North Carolina early next week, including some
mountainous areas which are more prone to flash flooding. All areas
seeing heavy rainfall from Irma will experience a risk of flooding
and flash flooding.

FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 22.1N 76.5W 135 KT 155 MPH
12H 09/0600Z 22.4N 78.2W 135 KT 155 MPH
24H 09/1800Z 23.0N 79.9W 135 KT 155 MPH
36H 10/0600Z 24.1N 81.0W 140 KT 160 MPH
48H 10/1800Z 25.7N 81.5W 125 KT 145 MPH
72H 11/1800Z 30.6N 83.0W 50 KT 60 MPH...INLAND
96H 12/1800Z 35.0N 85.9W 25 KT 30 MPH...INLAND
120H 13/1800Z 35.6N 87.0W 20 KT 25 MPH...POST-TROP/INLAND

$$
Forecaster Avila

[Sciencerocks]

000
URNT15 KWBC 082109
NOAA2 2311A IRMA HDOB 11 20170908
205930 2230N 07729W 6953 03023 9858 +110 +109 034083 084 054 005 00
210000 2230N 07727W 6957 03011 9847 +113 +109 032084 084 057 004 00
210030 2229N 07725W 6940 03021 9835 +114 +108 030084 085 059 005 00
210100 2228N 07723W 6960 02991 9822 +119 +110 030084 084 060 006 00
210130 2228N 07721W 6953 02988 9805 +124 +109 030083 084 061 007 00
210200 2227N 07719W 6950 02986 9790 +130 +097 029081 083 061 009 00
210230 2226N 07717W 6961 02962 9779 +130 +104 033083 084 064 008 00
210300 2226N 07716W 6960 02952 9767 +130 +104 033088 090 067 007 00
210330 2225N 07714W 6950 02958 9764 +126 +099 031090 091 067 010 00
210400 2224N 07712W 6954 02937 9741 +133 +101 029093 093 070 009 00
210430 2224N 07710W 6953 02924 9727 +131 +093 031097 100 075 005 00
210500 2223N 07708W 6958 02898 9713 +125 +101 035104 106 076 004 00
210530 2222N 07706W 6951 02887 9690 +127 +100 037111 113 080 002 00
210600 2222N 07705W 6957 02859 9663 +130 +093 038117 118 087 002 00
210630 2221N 07703W 6946 02844 9631 +131 +102 040123 124 091 005 00
210700 2221N 07702W 6952 02812 9601 +135 +113 039127 128 089 006 00
210730 2220N 07700W 6955 02785 9574 +136 +115 040131 131 095 015 00
210800 2220N 07659W 6952 02757 9537 +141 +117 039136 139 102 019 00
210830 2219N 07657W 6961 02716 9506 +135 +129 040132 137 114 031 03
210900 2219N 07656W 6907 02735 9446 +143 //// 041119 124 120 010 05

139 x .9 =125 knots at surface
with a 120 knot smrf.

[KBBOCA]

I just had at least 16 different flood warnings land in my Twitter feed from NWS Tampa Bay over a 10 minute period.

And then this from Dr. Knabb. We've not been talking about flooding risk so much. The story has been surge & winds, but now sounds like flooding too is becoming a bigger concern:

 https://twitter.com/DrRickKnabb/status/906263830572957696

[caneman]

I've noticed that storms with disruption to their inner corse structure after passing over land (commonly the Yucatán) never really get it together again until they're well clear of land.

I imagine the situation here is similar, and she's struggling to complete the ERC due to interaction with Cuba.

That wasn't the case with Harvey

[otterlyspicey]

I have two questions regarding the Keys:

1) I, like several of you, know people who have chosen to stay there in the Keys (Key West, specifically) for whatever reason. Is there a "loose" time that you'd guesstimate that it absolutely would be too late for them to leave if they change their mind right at the last minute? I'm getting so nervous for them.

2) Are the bridges throughout the Keys strong enough to support the hell that Irma is going to bring? Or are we looking at the possibility that these bridges may be at risk, stranding those without a boat on/off the Keys?

[norva]

NHC keeping it a 4 for now

[KBBOCA]

 https://twitter.com/JimCantore/status/906265587181084672

[caneseddy]

Ed Rappaport (acting NHC director) just stated on NBC6 that the current slow down is the signal that the turn may be starting soon.

He also said that with the current forecast track the strongest winds (which extend 30 miles from the eye) will be passing just west of the SE metro areas but that any shifts overnight and into tomorrow will be critical because either Cat 3-4 conditions for Southeast Florida or "if we are lucky" Cat 1-2 conditions and that it is too soon to know

Also says anyone in the Keys needs to leave now

[Evil Jeremy]

I just had at least 16 different flood warnings land in my Twitter feed from NWS Tampa Bay over a 10 minute period.

And then this from Dr. Knabb. We've not been talking about flooding risk so much. The story has been surge & winds, but now sounds like flooding too is becoming a bigger concern:

https://twitter.com/DrRickKnabb/status/ ... 0572957696

Makes sense that flooding is becoming a bigger concern. When it looked like Irma would ride up the East Coast, that would have kept the storm's backside over open waters. Eye goes to the West Coast, the vast plume of moisture on her right side must go inland.

[Sciencerocks]

000
URNT15 KWBC 082119
NOAA2 2311A IRMA HDOB 12 20170908
210930 2218N 07654W 6946 02659 9410 +150 //// 041117 120 123 004 01
211000 2218N 07652W 6938 02636 9371 +151 //// 045109 113 119 004 01
211030 2216N 07651W 6972 02559 9319 +174 +158 045091 094 109 003 00
211100 2215N 07649W 6946 02569 9284 +189 +132 050076 080 106 002 03
211130 2213N 07648W 6957 02535 9255 +200 +128 052062 067 056 002 00
211200 2212N 07646W 6961 02515 9238 +203 +117 052047 051 045 002 00
211230 2210N 07645W 6951 02522 9231 +203 +111 047034 038 035 002 00
211300 2209N 07643W 6949 02519 9226 +202 +112 041019 024 022 001 00
211330 2207N 07642W 6957 02508 9229 +193 +140 037006 009 014 001 03
211400 2206N 07640W 6963 02507 9236 +190 +160 239008 013 010 002 00
211430 2205N 07638W 6961 02518 9252 +180 +162 229022 025 015 002 00
211500 2204N 07636W 6957 02532 9266 +173 +167 224028 029 017 002 03
211530 2206N 07634W 6960 02527 9267 +175 +164 210030 034 029 000 03
211600 2207N 07632W 6955 02542 9273 +177 +155 187040 045 032 001 00
211630 2208N 07630W 6971 02531 9286 +176 +156 178054 058 038 003 00
211700 2210N 07627W 6971 02550 9301 +180 +156 172065 069 053 004 00
211730 2211N 07625W 6960 02595 9340 +169 +159 173079 082 092 006 00
211800 2212N 07623W 6953 02635 9388 +154 //// 173095 104 113 023 01
211830 2213N 07621W 6953 02686 9454 +139 //// 169111 116 117 035 05
211900 2214N 07619W 6944 02756 9529 +125 //// 162129 133 113 064 05

Pressure appears to be slightly down compared to earlier.

123 knot smrf found...

[Evil Jeremy]

Ed Rappaport (acting NHC director) just stated on NBC6 that the current slow down is the signal that the turn may be starting soon

Which turn?

[stormreader]

First time we've seen a strengthening indication on their discussion.

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM

Hurricane Irma Discussion Number 39
NWS National Hurricane Center Miami FL AL112017
500 PM EDT Fri Sep 08 2017

Latest data from an Air Force Hurricane Hunter plane a few hours ago
indicate that Irma's intensity continues to fluctuate, and the
winds are estimated at 135 kt. The last minimum central pressure
was 925 mb. Another reconnaissance plane will check Irma soon.

The environment is favorable for Irma to maintain its category 4
status, and only unpredictable eyewall replacement cycles could
result in intensity fluctuations during the next 48 hours. The
interaction of the hurricane's circulation with Cuba will probably
not result in any relevant change in intensity. In summary, the NHC
forecast brings Irma near south Florida as a category 4 hurricane.
After landfall, interaction with land and an increase in wind shear
should induce gradual weakening.

Satellite images and radar fixes from Cuba indicate that Irma has
slowed down and is now moving toward the west or 280 degrees at
about 10 kt. The hurricane should continue on this track for the
next 12 hours to 24 hours, and this track will bring the core of
Irma very close to the north coast of Cuba. After that time, Irma
should reach the southwestern edge of the subtropical high and begin
to move toward the northwest and north-northwest toward the Florida
peninsula. The precise moment of this turn is still uncertain, and
that is why NHC emphasizes that nobody should focus on the exact
track of the center. This afternoon's NHC forecast was again
adjusted a little bit westward following the trend of the ECMWF
model and both the HFIP corrected consensus and the FSU
Superensemble. In fact, these 3 aids continued to be tightly packed.

KEY MESSAGES:

1. Irma will continue to bring life-threatening wind, storm surge,
and rainfall hazards to portions of the Bahamas and the north coast
of Cuba, especially over the adjacent Cuban Keys, through Saturday.

2. Irma is expected to make landfall in Florida as an extremely
dangerous major hurricane, and will bring life-threatening wind
impacts to much of the state regardless of the exact track of the
center.

3. There is the danger of life-threatening storm surge inundation in
southern Florida and the Florida Keys during the next 36 hours,
where a Storm Surge Warning is in effect. The threat of significant
storm surge flooding along the southwest coast of Florida has
increased, and 8 to 12 feet of inundation above ground level is
possible in this area. This is a life-threatening situation.
Everyone in these areas should take all actions to protect life and
property from rising water and follow evacuation instructions from
local officials.

4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 8 to 15 inches, with isolated amounts of
20 inches are expected over the Florida Keys and much of the Florida
peninsula through Tuesday night. The highest amounts are expected
over the eastern Florida peninsula and upper Florida Keys. Irma
will likely bring periods of heavy rain to much of Georgia, South
Carolina, and western North Carolina early next week, including some
mountainous areas which are more prone to flash flooding. All areas
seeing heavy rainfall from Irma will experience a risk of flooding
and flash flooding.

FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 22.1N 76.5W 135 KT 155 MPH
12H 09/0600Z 22.4N 78.2W 135 KT 155 MPH
24H 09/1800Z 23.0N 79.9W 135 KT 155 MPH
36H 10/0600Z 24.1N 81.0W 140 KT 160 MPH
48H 10/1800Z 25.7N 81.5W 125 KT 145 MPH
72H 11/1800Z 30.6N 83.0W 50 KT 60 MPH...INLAND
96H 12/1800Z 35.0N 85.9W 25 KT 30 MPH...INLAND
120H 13/1800Z 35.6N 87.0W 20 KT 25 MPH...POST-TROP/INLAND

$$
Forecaster Avila

You have to think that without significant land interaction with Cuba, its a decent possibility. Central structure of storm still looks fine. As it actually makes the turn is probably a good bet for the time of intensification. During the sharp turn itself. Oh, sorry for my earlier post. Storm not in yet, very delicate situation. Land interaction itself, could possibly even influence a shift one way or another of a few miles or so. Apologize.

[Kat5]

Ed Rappaport (acting NHC director) just stated on NBC6 that the current slow down is the signal that the turn may be starting soon

Which turn?

Exactly going west on the SAT loop

[bjackrian]

Looks like a drop to 923 mb if I'm reading the HDOB correctly:

211200 2212N 07646W 6961 02515 9238 +203 +117 052047 051 045 002 00
211230 2210N 07645W 6951 02522 9231 +203 +111 047034 038 035 002 00
211300 2209N 07643W 6949 02519 9226 +202 +112 041019 024 022 001 00
211330 2207N 07642W 6957 02508 9229 +193 +140 037006 009 014 001 03
211400 2206N 07640W 6963 02507 9236 +190 +160 239008 013 010 002 00

Edited: And with some surface wind. I'm not sure of the correction factor for surface winds.

[AutoPenalti]

Ed Rappaport (acting NHC director) just stated on NBC6 that the current slow down is the signal that the turn may be starting soon

I don't think its slowing down... it's still moving at a decent clip.

[stormreader]

NHC keeping it a 4 for now

True, but see Tolakram's post about decent possibility of 160 mph at landfall (according to NHC). Could even be a little conservative.

[fci]

yeah the west movement has stopped to me and I suspect the models were picking up on this jog and shifted west to compensate. Would not be surprised if they swung a tad east now on tonight's runs with Gonzo flying. Personally, until the NWS can pin point an actual track they are going on best guess in winds for Miami. If she does shift east those forecasts will need to be amended to show increased impacts....JMO...

Are you getting a feel for a shift a bit east or is it becoming established that the westward movement has sealed the west movement from today to be firm?