Tropical Storm Isaac, Part 2: Isaac Moving Into The Gulf Of Mexico-Hurricane Warnings For Morgan City, LA/MS/AL & FL Panhandle To Destin, FL

[dan88]

000

URNT12 KNHC 242140

VORTEX DATA MESSAGE AL092012

A. 24/21:15:10Z

B. 17 deg 06 min N

071 deg 46 min W

C. 850 mb 1374 m

D. 50 kt

E. 090 deg 44 nm

F. 001 deg 43 kt

G. 253 deg 62 nm

H. 994 mb

I. 17 C / 1524 m

J. 18 C / 1525 m

K. 17 C / NA

L. OPEN WEST

M. C16

N. 12345 / 8

O. 0.02 / 3 nm

P. AF300 1209A ISAAC OB 10

MAX FL WIND 70 KT E QUAD 18:21:30Z

MAX FL TEMP 18 C 251 / 19 NM FROM FL CNTR

RAGGED EYE PRESENTATION ON RADAR

[HurricaneJosh]

B. 17 deg 06 min N

071 deg 46 min W

That's SE of the advisory position.

[Ground Scouring]

Frankly, the longer the short-term WNW movement continues, and if other models join the GFS and some of its ensembles in seeing a NNW movement over E Cuba before turning back, then I would start to become more enthusiastic about a hurricane in the upper Keys/Miami area, now that Isaac at last has a decent inner core in spite of Hispaniola. Yes, convection is weak, but a well-defined LLC is a large improvement. I see some further Haitian interaction, but not so much that it would kill the developing inner core.

[gkrangers]

No temp gradient.

[phil882]

000

URNT12 KNHC 242140

VORTEX DATA MESSAGE AL092012

A. 24/21:15:10Z

B. 17 deg 06 min N

071 deg 46 min W

C. 850 mb 1374 m

D. 50 kt

E. 090 deg 44 nm

F. 001 deg 43 kt

G. 253 deg 62 nm

H. 994 mb

I. 17 C / 1524 m

J. 18 C / 1525 m

K. 17 C / NA

L. OPEN WEST

M. C16

N. 12345 / 8

O. 0.02 / 3 nm

P. AF300 1209A ISAAC OB 10

MAX FL WIND 70 KT E QUAD 18:21:30Z

MAX FL TEMP 18 C 251 / 19 NM FROM FL CNTR

RAGGED EYE PRESENTATION ON RADAR

Despite the lack of deeper convection, the inner core is beginning to organize. This is evident looking at visible imagery as well as IR which is starting to show a formative eyewall.

[PSUBlizzicane2007]

Despite the lack of deeper convection, the inner core is beginning to organize. This is evident looking at visible imagery as well as IR which is starting to show a formative eyewall.

Yup....and let's not forget the diurnal minimum.... overnight tonight could be more exciting for deeper convection formation.

[Derecho!]

RAGGED EYE PRESENTATION ON RADAR

Yehaww....

I note that it's Diurnal Minimum and there are a couple of new little pharts of convection in the eyewall, so it may not be going to pot just yet.

[dan11295]

Noticed that the heaviest convection is now on the east side of Isaac. That is rather ugly for Haiti wrt to rainfall. At least it is moving and not a Jeanne scenario. Regarding movement, more it goes NW, less risk of it going over the spine of Cuba. Don't really see much model support for Isaac moving inland over S. FL either. Might clip the Everglades but thats about it I think.

[Derecho!]

Disturbingly, the 18Z NOGAPS follows the NHC forecast track almost perfectly...

Considering it's impossible for NOGAPS to be correct.

[HurricaneJosh]

Despite the lack of deeper convection, the inner core is beginning to organize. This is evident looking at visible imagery as well as IR which is starting to show a formative eyewall.

Yup....and let's not forget the diurnal minimum.... overnight tonight could be more exciting for deeper convection formation.

I don't see how this is significant. It's about to go into the blender.

At this point, it would actually be better if it doesn't have this cute little "core"-- a loose circulation would have a better chance.

[Srain]

I don't see how this is significant. It's about to go into the blender.

At this point, it would actually be better if it doesn't have this cute little "core"-- a loose circulation would have a better chance.

Not really going to make one bit of difference in the 'grand scheme of things'...

[PSUBlizzicane2007]

I don't see how this is significant. It's about to go into the blender.

At this point, it would actually be better if it doesn't have this cute little "core"-- a loose circulation would have a better chance.

Again, remember, the SW peninsula is not nearly as dire as the central cordillera. Isaac will be fine, even if weaker. There is time before it makes landfall for Isaac to feel the beginning effects of diurnal maximum.

[ALhurricane]

18z GFS is back to the AL/FL line.

[icebreaker5221]

This analogues haven't been that good so far, but it's now giving some more reasonable solutions. Probably some blended intensity / track combination of Ernesto, Gustav, Charley, Dennis would verify quite nicely.

[DaculaWeather]

Go here and click on Visible Loop. Beautiful shot right before it gets dark. Very impressive looking http://www.daculaweather.com/4_sat_caribbean.php

[HurricaneJosh]

Again, remember, the SW peninsula is not nearly as dire as the central cordillera. Isaac will be fine, even if weaker. There is time before it makes landfall for Isaac to feel the beginning effects of diurnal maximum.

Well... Maybe you're right. I hope so.

18z GFS is back to the AL/FL line.

This analogues haven't been that good so far, but it's now giving some more reasonable solutions. Probably some blended intensity / track combination of Ernesto, Gustav, Charley, Dennis would verify quite nicely.

And that would be Dennis, which is kind of the median of all that.

[PSUBlizzicane2007]

18z GFS is back to the AL/FL line.

There are two interesting incidents on the 18Z GFS:

1. The pulling of Isaac towards Andros Island, then a sudden westward movement through the middle/upper Keys and extreme southern Everglades.

2. The stalling of Isaac just NW of Mobile.

Two completely new things showing up in the GFS. Perhaps the new G-IV info will provide some clarification at 00Z.

[icebreaker5221]

Well... Maybe you're right. I hope so.

And that would be Dennis, which is kind of the median of all that.

I said blend, but I didn't say linear blend. I would weigh Ernesto more heavily the next 48 hrs, then maybe Dennis thereafter.

[HurricaneJosh]

I said blend, but I didn't say linear blend. I would weigh Ernesto more heavily the next 48 hrs, then maybe Dennis thereafter.

OK, I'm thinking just of the ultimate landfall point, and something W of the Peninsula still seems more likely to me than something on the other (Ernesto) side. Not sure of the quality of it when it comes ashore...

[Ground Scouring]

The models over the next 48 hours seem to be having trouble analyzing both the energy in the splitting southern Plains trough as well as the fractured trough/cut-off low over NC and its effects on the ridging to the south. However, the trend on the GFS has been to grant more energy to the split Plains trough, while the ECMWF does not. In my experience, the GFS has tended to overestimate the number of split shortwave features in the northern branch, while the ECMWF this year has tended to underestimate them to some degree. Perhaps blending the two solutions might be a prudent course of action, which would still support the NNW pulling of Isaac over the next 24 hours before turning back NW.

[wi_fl_wx]

Isaac is developing a 37 GHz ring feature which is an early sign of rapid intensification (Kieper and Jiang 2012). Obviously RI is not going to occur because of land interaction, but if Isaac can retain or quickly reform a cyan ring after moving north of Cuba (indicative of warm rain surrounding a developing eyewall), it will have a good chance at RI as it approaches the Florida Keys. At this point I would not count on that happening, but it is definitely a possibility.

[Srain]

Product: Air Force Vortex Message (URNT12 KNHC)

Transmitted: 24th day of the month at 22:47Z

Corrected: This observation corrected a previous observation.

Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 300)

Storm Number & Year: 09L in 2012

Storm Name: Isaac (flight in the North Atlantic basin)

Mission Number: 12

Observation Number: 14

A. Time of Center Fix: 24th day of the month at 22:27:20Z

B. Center Fix Coordinates: 17°03'N 71°50'W (17.05N 71.8333W)

B. Center Fix Location: 108 miles (174 km) to the SSE (162°) from Port-au-Prince, Haiti.

C. Minimum Height at Standard Level: 1,374m (4,508ft) at 850mb

D. Estimated (by SFMR or visually) Maximum Surface Wind: 57kts (~ 65.6mph)

E. Location of the Estimated Maximum Surface Wind: 43 nautical miles (49 statute miles) to the NE (45°) of center fix

F. Maximum Flight Level Wind Inbound: From 144° at 60kts (From the SE at ~ 69.0mph)

G. Location of Maximum Flight Level Wind Inbound: 74 nautical miles (85 statute miles) to the NE (52°) of center fix

H. Minimum Sea Level Pressure: 993mb (29.32 inHg)

I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 14°C (57°F) at a pressure alt. of 1,524m (5,000ft)

J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 18°C (64°F) at a pressure alt. of 1,525m (5,003ft)

K. Dewpoint Temp (collected at same location as temp inside eye): 18°C (64°F)

K. Sea Surface Temp (collected at same location as temp inside eye): Not Available

L. Eye Character: Not Available

M. Eye Shape: Not Available

N. Fix Determined By: Penetration, Wind, Pressure and Temperature

N. Fix Levels (sfc and flt lvl centers are within 5nm of each other): Surface and 850mb

O. Navigation Fix Accuracy: 0.02 nautical miles

O. Meteorological Accuracy: 3 nautical miles

Remarks Section:

Maximum Flight Level Wind: 64kts (~ 73.6mph) in the east quadrant at 21:41:30Z

Maximum Flight Level Temp: 19°C (66°F) which was observed 6 nautical miles to the N (9°) from the flight level center

[thewxmann]

The models over the next 48 hours seem to be having trouble analyzing both the energy in the splitting southern Plains trough as well as the fractured trough/cut-off low over NC and its effects on the ridging to the south. However, the trend on the GFS has been to grant more energy to the split Plains trough, while the ECMWF does not. In my experience, the GFS has tended to overestimate the number of split shortwave features in the northern branch, while the ECMWF this year has tended to underestimate them to some degree. Perhaps blending the two solutions might be a prudent course of action, which would still support the NNW pulling of Isaac over the next 24 hours before turning back NW.

The blend is definitely the best way to go right now. I really think more data from that Plains trough would help the models more than the GIV data and the special 18Z soundings that are being released, although those are nevertheless helpful.

[Ground Scouring]

The blend is definitely the best way to go right now. I really think more data from that Plains trough would help the models more than the GIV data and the special 18Z soundings that are being released, although those are nevertheless helpful.

The one thing I will say is that in these cases, in which the interaction is among a split shortwave trough in the northern stream, a downstream cut-off low over NC, and downstream ridging over Isaac, is that usually, if and when the models tend to bust, they tend to bust on the west side. Synoptically, especially if the system is deeper in the short term than projected, upper-level features that produce temporary weaknesses in the large-scale ridging, leaving a narrow shortwave ridge-bridge behind, tend to be underestimated. Thus, if Isaac is stronger than expected once it moves over the Mona Passage, or re-intensifies faster off NE Cuba, its depth, combined with even a slight underestimation of the weakness, could mean the difference between a middle Keys and a Greater Miami landfall (and, consequently, the difference between a FL/AL border strike and a landfall nearest Apalachicola). I would also keep in mind that the current intensity of Isaac, 993 mb, is actually a bit greater than some models like the GFS forecasted.

[PSUBlizzicane2007]

BTW, here is an important radar link for the eastern tip of Cuba: http://www.insmet.cu.../gpdMAXw01a.gif

NOTE: Please do not hotlink the Cuban radar images directly to this site as it is VERY slow.

Jamaica has a radar too... but it's kind of bad.

[U_Thant]

BTW, here is an important radar link for the eastern tip of Cuba: http://www.insmet.cu.../gpdMAXw01a.gif

NOTE: Please do not hotlink the Cuban radar images directly to this site as it is VERY slow.

Jamaica has a radar too... but it's kind of bad.

I hadn't checked this in years, but it appears that the radar in GITMO is up and running too.

http://radar.weather...ct=N0R&loop=yes

It's just a ARSR-4 (Airport Surveillance Radar) and it only displays base ref, close range, but still...it's something.

[wxsmwhrms]

The thing I have the biggest problem with the GFS is its speed. It has it getting to the northern Gulf coast by 12z Tue which is about a day faster than the UK and EC. Systems being moved by a ridge toward a weakness aren't typically known for moving on the fast side of guidance.

The global models are probably within about 75 miles as the crow flies now with the final landfall point.

[dan88]

000

URNT12 KNHC 242328

VORTEX DATA MESSAGE AL092012

A. 24/23:16:20Z

B. 17 deg 00 min N

071 deg 57 min W

C. 850 mb 1375 m

D. 36 kt

E. 123 deg 31 nm

F. 206 deg 44 kt

G. 126 deg 41 nm

H. 994 mb

I. 17 C / 1518 m

J. 18 C / 1526 m

K. 17 C / NA

L. NA

M. NA

N. 1345 / 08

O. 0.02 / 2 nm

P. AF300 1209A ISAAC OB 18

MAX FL WIND 64 KT E QUAD 21:41:30Z

MAX FL TEMP 18 C 109 / 12 NM FROM FL CNTR

[HurricaneJosh]

Each fix is a hair S of the previous one. It seems to be nudging due W or just S of due W.

[HurricaneJosh]

Despite the center fixes, they put the center at 17.3N 72.0W in the new advisory. Is this just a continuity value? It's really more like 17.0N 72.0W.