ATL: IRMA - Post-Tropical - Discussion

[Blown Away]

nhc is favoring the gulf it looks like

No, it's not. The cone of uncertainty is pretty wide at that point with Florida in the middle. If the 12z 's continue the eastward shift that the 6z's started this morning, the portion of the cone that is in the gulf now will be mostly gone by the 5pm update.

The Cone has nothing to do with Model runs. It has to do with the Official NHC Forecast track and then the cone is decided based on the amount of miles error there historically has been at each forecast point. So the only way the Cone will move out of the GoM is if the NHC moves their forecast.

If models remain about the same we should see the next advisory show the turn to NW... That turn on the models started @126 hours and the NHC 5 day goes out 120 hours... Next advisory, probably through upper Keys into Everglades City area I'm guessing...

[GCANE]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 5th day of the month at 15:20Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF99-5309
Storm Number & Year: 11 in 2017
Storm Name: Irma (flight in the North Atlantic basin)
Mission Number: 8
Observation Number: 15 ( See all messages of this type for this mission. )
A. Time of Center Fix: 5th day of the month at 14:49:00Z
B. Center Fix Coordinates: 16°46'N 58°30'W (16.7667N 58.5W)
B. Center Fix Location: 216 statute miles (348 km) to the ENE (62°) from Roseau, Dominica.
C. Minimum Height at Standard Level: 2,454m (8,051ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 147kts (~ 169.2mph)
E. Location of the Estimated Maximum Surface Wind Inbound: 20 nautical miles (23 statute miles) to the ENE (67°) of center fix
F. Maximum Flight Level Wind Inbound: From 160° at 142kts (From the SSE at ~ 163.4mph)
G. Location of Maximum Flight Level Wind Inbound: 22 nautical miles (25 statute miles) to the ENE (67°) of center fix
H. Minimum Sea Level Pressure: 927mb (27.38 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 8°C (46°F) at a pressure alt. of 3,022m (9,915ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 19°C (66°F) at a pressure alt. of 3,050m (10,007ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 10°C (50°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Closed
M. Eye Shape & Diameter: Circular with a diameter of 25 nautical miles (29 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile

Remarks Section:
Maximum Flight Level Wind: 147kts (~ 169.2mph) which was observed 17 nautical miles (20 statute miles) to the NE (46°) from the flight level center at 12:57:00Z
Maximum Flight Level Wind Outbound: 127kts (~ 146.1mph) which was observed 11 nautical miles (13 statute miles) to the SW (225°) from the flight level center at 14:52:30Z
Dropsonde Surface Wind at Center: From 335° at 7kts (From the NNW at 8mph)
Maximum Flight Level Temp: 20°C (68°F) which was observed 8 nautical miles to the ENE (65°) from the flight level center

[EquusStorm]

The bit noting this is the strongest Atlantic hurricane outside the Caribbean or Gulf has been mentioned as it's in the advisory, but this has a real chance of striking the US as a category four... which would be the second of the year... which I think has never happened before that we know of. Not that there is a huge difference between 125 and 130 or so, per se, but even notorious Atlantic seasons have failed to do that. 2005's strongest landfall was category three. 2008's was category two. A single US category four landfall is statistically quite rare. 2004 came close after having one with Charley, but Ivan had weakened to a category three by landfall.

This is not an especially fun record to be talking about potentially setting.

[Evil Jeremy]

nhc is favoring the gulf it looks like

No, it's not. The cone of uncertainty is pretty wide at that point with Florida in the middle. If the 12z 's continue the eastward shift that the 6z's started this morning, the portion of the cone that is in the gulf now will be mostly gone by the 5pm update.

The Cone has nothing to do with Model runs. It has to do with the Official NHC Forecast track and then the cone is decided based on the amount of miles error there historically has been at each forecast point. So the only way the Cone will move out of the GoM is if the NHC moves their forecast.

Yes, but none of the operational models see this getting further west than the Florida Panhandle the moment. At this point, nothing favors a GOM threat (outside of the west coast of Florida). It seems like the models have honed in on their 5 day forecast.

[Tekken_Guy]

Why is its pressure so high? It should be at least as low as Ivan's.

[Aric Dunn]

IR sat showing a decrease in the real clod cloud tops so could have weakened slightly. lets hope a for a ERC while it passes the islands..

no concentric features yet...
its in radar range..

http://barbadosweather.org/Composite/ki ... site=Sabre

[Patrick99]

The bit noting this is the strongest Atlantic hurricane outside the Caribbean or Gulf has been mentioned as it's in the advisory, but this has a real chance of striking the US as a category four... which would be the second of the year... which I think has never happened before that we know of. Not that there is a huge difference between 125 and 130 or so, per se, but even notorious Atlantic seasons have failed to do that. 2005's strongest landfall was category three. 2008's was category two. A single US category four landfall is statistically quite rare. 2004 came close after having one with Charley, but Ivan had weakened to a category three by landfall.

This is not an especially fun record to be talking about potentially setting.

Strongest Atlantic hurricane outside Caribbean or Gulf.....wait, what about the 1935 Labor Day storm? Are the FL Straits considered "the Gulf?" I always considered the Atlantic side of the Keys to be, well, the Atlantic.

[meriland29]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 5th day of the month at 15:20Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF99-5309
Storm Number & Year: 11 in 2017
Storm Name: Irma (flight in the North Atlantic basin)
Mission Number: 8
Observation Number: 15 ( See all messages of this type for this mission. )
A. Time of Center Fix: 5th day of the month at 14:49:00Z
B. Center Fix Coordinates: 16°46'N 58°30'W (16.7667N 58.5W)
B. Center Fix Location: 216 statute miles (348 km) to the ENE (62°) from Roseau, Dominica.
C. Minimum Height at Standard Level: 2,454m (8,051ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 147kts (~ 169.2mph)
E. Location of the Estimated Maximum Surface Wind Inbound: 20 nautical miles (23 statute miles) to the ENE (67°) of center fix
F. Maximum Flight Level Wind Inbound: From 160° at 142kts (From the SSE at ~ 163.4mph)
G. Location of Maximum Flight Level Wind Inbound: 22 nautical miles (25 statute miles) to the ENE (67°) of center fix
H. Minimum Sea Level Pressure: 927mb (27.38 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 8°C (46°F) at a pressure alt. of 3,022m (9,915ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 19°C (66°F) at a pressure alt. of 3,050m (10,007ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 10°C (50°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Closed
M. Eye Shape & Diameter: Circular with a diameter of 25 nautical miles (29 statute miles)
N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigational Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 1 nautical mile

Remarks Section:
Maximum Flight Level Wind: 147kts (~ 169.2mph) which was observed 17 nautical miles (20 statute miles) to the NE (46°) from the flight level center at 12:57:00Z
Maximum Flight Level Wind Outbound: 127kts (~ 146.1mph) which was observed 11 nautical miles (13 statute miles) to the SW (225°) from the flight level center at 14:52:30Z
Dropsonde Surface Wind at Center: From 335° at 7kts (From the NNW at 8mph)
Maximum Flight Level Temp: 20°C (68°F) which was observed 8 nautical miles to the ENE (65°) from the flight level center

Is that the latest? So she is around 170mph?

[MississippiWx]

Unfortunately, a Northern Leewards direct hit looks unavoidable at this point. Irma continues on a stubborn due west path.

Irma is exactly on track...

A wobble north put it more on track, but it is still a hair south of the next point on its current motion. Doesn't change the fact that it's on a direct path to hit the Northern Leewards. Not sure if you're trying to deny that point or what.

[NJWxHurricane]

Unfortunately, a Northern Leewards direct hit looks unavoidable at this point. Irma continues on a stubborn due west path.

Irma is exactly on track...

A wobble north put it more on track, but it is still a hair south of the next point on its current motion. Doesn't change the fact that it's on a direct path to hit the Northern Leewards. Not sure if you're trying to deny that point or what.

except this isn't on a due west track, that's what he's trying to tell you..

[NJWxHurricane]

Unfortunately, a Northern Leewards direct hit looks unavoidable at this point. Irma continues on a stubborn due west path.

Irma is exactly on track...

A wobble north put it more on track, but it is still a hair south of the next point on its current motion. Doesn't change the fact that it's on a direct path to hit the Northern Leewards. Not sure if you're trying to deny that point or what.

and it's also not a wobble, w or wsw movement has stopped, wnw movement has begun

[dukeblue219]

Strongest Atlantic hurricane outside Caribbean or Gulf.....wait, what about the 1935 Labor Day storm? Are the FL Straits considered "the Gulf?" I always considered the Atlantic side of the Keys to be, well, the Atlantic.

I believe they are referencing only max sustained wind at 180mph as the qualifier. The 1935 storm peaked at 160mph (as far as we know). There are certainly storms with lower pressure in the Atlantic still.

[xtyphooncyclonex]

Unsurprisingly turning west-northwest while strengthening. Btw, is Irma's pressure 929 mb or 931??

[Patrick99]

Strongest Atlantic hurricane outside Caribbean or Gulf.....wait, what about the 1935 Labor Day storm? Are the FL Straits considered "the Gulf?" I always considered the Atlantic side of the Keys to be, well, the Atlantic.

I believe they are referencing only max sustained wind at 180mph as the qualifier. The 1935 storm peaked at 160mph (as far as we know). There are certainly storms with lower pressure in the Atlantic still.

Good point....I guess we can't substantiate some of those claims of 200mph winds in that storm.

[dukeblue219]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 5th day of the month at 15:20Z
[...]
Remarks Section:
Maximum Flight Level Wind: 147kts (~ 169.2mph) which was observed 17 nautical miles (20 statute miles) to the NE (46°) from the flight level center at 12:57:00Z

Is that the latest? So she is around 170mph?

Based on that vortex message, yes, that's the highest they observed. The NHC doesn't base their max sustained winds purely on individual measurements, though, and could well keep it at 155kt based on the 147kt measurement (it's pretty close) along with other evidence they consider (dropping pressure, for example).

[Iune]

Unsurprisingly turning west-northwest while strengthening. Btw, is Irma's pressure 929 mb or 931??

The NHC advisory has Irma at 929.

[cjrciadt]

Unsurprisingly turning west-northwest while strengthening. Btw, is Irma's pressure 929 mb or 931??

927 latest dropsonde

[Vdogg]

nhc is favoring the gulf it looks like

No, it's not. The cone of uncertainty is pretty wide at that point with Florida in the middle. If the 12z 's continue the eastward shift that the 6z's started this morning, the portion of the cone that is in the gulf now will be mostly gone by the 5pm update.

The Cone has nothing to do with Model runs. It has to do with the Official NHC Forecast track and then the cone is decided based on the amount of miles error there historically has been at each forecast point. So the only way the Cone will move out of the GoM is if the NHC moves their forecast.

If the NHC does not use the models to help determine their track, then why do they talk about the models in their forecast discussions? This makes no sense.

[Vdogg]

No, it's not. The cone of uncertainty is pretty wide at that point with Florida in the middle. If the 12z 's continue the eastward shift that the 6z's started this morning, the portion of the cone that is in the gulf now will be mostly gone by the 5pm update.

The Cone has nothing to do with Model runs. It has to do with the Official NHC Forecast track and then the cone is decided based on the amount of miles error there historically has been at each forecast point. So the only way the Cone will move out of the GoM is if the NHC moves their forecast.

Yes, but none of the operational models see this getting further west than the Florida Panhandle the moment. At this point, nothing favors a GOM threat (outside of the west coast of Florida). It seems like the models have honed in on their 5 day forecast.

Not to mention that the NHC constantly refers to model guidance in their forecast discussions. They obviously take that stuff into account.

[tropicwatch]

Unsurprisingly turning west-northwest while strengthening. Btw, is Irma's pressure 929 mb or 931??

927 according to latest recon vortex.