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Hurricane Sandy - LIVE - Meteorological Discussion


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Finally, TS winds in the SE quad where there is strong convection, 45FL/52SFMR with several SFMR obs above 35kts...the highest are probably rain contaminated, but there are a few which aren't, so I guess it's about to become 35kts TS Sandy in the next advisory

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Pressure down to 999mbs (2mb drop from last fix) with 27 knot SFMR winds.

Seems like they're having a hard time locating the center.

I believe I saw a 33 KT SFMR wind, but the page updated and I can't go back and look. Could have been rain contaminated, of course.

The system overall still appears poorly defined, though it is getting better. It may need another 3-6 hours to consolidate enough for TS status.

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NHC: it is Sandy.

WATCHES AND WARNINGS

--------------------

CHANGES WITH THIS ADVISORY...

THE GOVERNMENT OF HAITI HAS ISSUED A TROPICAL STORM WATCH FOR HAITI.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...

* JAMAICA

* HAITI

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE

POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS. A

HURRICANE WATCH AND/OR A TROPICAL STORM WARNING COULD BE REQUIRED

FOR JAMAICA TONIGHT.

INTERESTS IN EASTERN CUBA AND THE BAHAMAS SHOULD MONITOR THE

PROGRESS OF SANDY.

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I believe I saw a 33 KT SFMR wind, but the page updated and I can't go back and look. Could have been rain contaminated, of course.

The system overall still appears poorly defined, though it is getting better. It may need another 3-6 hours to consolidate enough for TS status.

I was actually referring to surface winds at the time of the 999mb readings.

000

WTNT33 KNHC 222057

TCPAT3

BULLETIN

TROPICAL STORM SANDY ADVISORY NUMBER 2

NWS NATIONAL HURRICANE CENTER MIAMI FL AL182012

500 PM EDT MON OCT 22 2012

...DEPRESSION STRENGTHENS INTO TROPICAL STORM SANDY...

SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION

----------------------------------------------

LOCATION...12.5N 78.5W

ABOUT 395 MI...640 KM SSW OF KINGSTON JAMAICA

MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H

PRESENT MOVEMENT...STATIONARY

MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES

GOES19152012296V87WbH.jpg

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Pressure down to 999mbs (2mb drop from last fix) with 27 knot SFMR winds.

Seems like they're having a hard time locating the center.

Well, they havent had a initial fix, so we don't know if its deepening yet. Not sure why they didnt go a tad south in that last leg, its obvious from earlier obs there were W winds just a bit south.

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000

URNT12 KNHC 222114

VORTEX DATA MESSAGE AL182012

A. 22/20:35:30Z

B. 12 deg 26 min N

078 deg 19 min W

C. NA

D. 39 kt

E. 077 deg 37 nm

F. 165 deg 42 kt

G. 071 deg 37 nm

H. EXTRAP 1001 mb

I. 22 C / 446 m

J. 24 C / 444 m

K. 22 C / NA

L. NA

M. NA

N. 13 / 01

O. 0.02 / 5 nm

P. AF301 01EEA INVEST OB 14

MAX FL WIND 42 KT E QUAD 20:20:30Z

SLP EXTRAP FROM BELOW 1500 FT

MAX FL TEMP 25 C 028 / 10 NM FROM FL CNTR

MIN SLP 999MB DISPLACED FROM WIND CTR 045/12NM

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While I seriously doubt the sub-950 mb solutions of the GEM and Euro, the track and evolution seem plausible and a blend of these with more appropriate 955-960 mb central pressure would result in a cat-2 landfall near NYC on the 30th. The GFS solutions from past few runs look totally wrong as they seem to fail to anticipate any real amplification of Pacific system now slowly gathering intensity.

When I combine the guidance of these apparently best-performing models with some research model factors, I note a strong potential for intensification between Oct 29 and Nov 2 so that I am led to believe that if the storm develops any sort of northward track it will undergo explosive development around the 29th.

My guess as to the day 5 intensity is 970 mb and cat-1 rather than the current TS forecast, and from there it should reach about 960 mb on day 6 at 31N 74W, then 950 mb on day 7 at 36N 73W on its way to a day 8 landfall 30-100 miles east of JFK, hopefully already weakening slightly at that point. This would suggest a landfall intensity somewhere in the range of strong cat-1 to weak cat-3 and of course anything stronger would represent a 1938-type outcome that would not be possible to predict until perhaps 36h before landfall.

There are ways that this could unfold without doing a whole lot of damage except locally near landfall, despite the very ominous look of the maps today. My scenario for example would probably be largely low-impact for the Mid-Atlantic and medium impact for NJ and NYC from flooding rainfalls, marginal wind damage, but locally high impact for LI and CT.

If that Euro 927.8 mb verified (I love the decimal precision) and that came ashore even at 945 mbs, it would do catastrophic damage from a combination of 140-knot wind gusts and 25-35 ft storm surges. This is by the way not my forecast, just a comment on what the map depiction would imply. The GGEM map would imply 120 knot winds in south-central NJ and 20-30 ft storm surges, major if not catastrophic damage between Cape May and New York City. But I think that coastal impact is less likely to verify than the Euro target zone further north.

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While I seriously doubt the sub-950 mb solutions of the GEM and Euro, the track and evolution seem plausible and a blend of these with more appropriate 955-960 mb central pressure would result in a cat-2 landfall near NYC on the 30th. The GFS solutions from past few runs look totally wrong as they seem to fail to anticipate any real amplification of Pacific system now slowly gathering intensity.

When I combine the guidance of these apparently best-performing models with some research model factors, I note a strong potential for intensification between Oct 29 and Nov 2 so that I am led to believe that if the storm develops any sort of northward track it will undergo explosive development around the 29th.

My guess as to the day 5 intensity is 970 mb and cat-1 rather than the current TS forecast, and from there it should reach about 960 mb on day 6 at 31N 74W, then 950 mb on day 7 at 36N 73W on its way to a day 8 landfall 30-100 miles east of JFK, hopefully already weakening slightly at that point. This would suggest a landfall intensity somewhere in the range of strong cat-1 to weak cat-3 and of course anything stronger would represent a 1938-type outcome that would not be possible to predict until perhaps 36h before landfall.

There are ways that this could unfold without doing a whole lot of damage except locally near landfall, despite the very ominous look of the maps today. My scenario for example would probably be largely low-impact for the Mid-Atlantic and medium impact for NJ and NYC from flooding rainfalls, marginal wind damage, but locally high impact for LI and CT.

If that Euro 927.8 mb verified (I love the decimal precision) and that came ashore even at 945 mbs, it would do catastrophic damage from a combination of 140-knot wind gusts and 25-35 ft storm surges. This is by the way not my forecast, just a comment on what the map depiction would imply. The GGEM map would imply 120 knot winds in south-central NJ and 20-30 ft storm surges, major if not catastrophic damage between Cape May and New York City. But I think that coastal impact is less likely to verify than the Euro target zone further north.

Re doubts about extreme model intensity- Sandy at the end of October near NYC (if that were to verify) would not be a tropical cyclone, and would have enhancement of serious baroclinic forcing. Not a red tag, don't know all the terms, but a powerful jet to the North putting the surface low in an upward motion region, and fairly close proximity of airmasses with temp and dewpoint deltas of 50º or more, well....

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A very cold CDO would do wonders where it's now parked with the current favorable upper level conditions.

I disagree--there has been no sign of a real CDO developing and the pulsating convective pattern, combined with a sharp dry slot east of the center, indicates both easterly shear as well as some possible low-level dry air intrusion off the NW continental edge of South America. Soundings from Panama City show the low-level dry air quite well. Also, the strongest moisture flux is well NE of the center, thus sustaining the prominent outer band...which, in turn, has been hampering the inflow to the center and preventing parcels from ascending to form an eye-wall. Unsurprisingly, the wind center, the pressure center, and the mid-level circulation are probably still a bit disjointed. As the system moves N within 24 hours, shear should already start to increase as the trough over W Cuba nudges the upper-level anticyclone to the east of Sandy, thereby increasing exposure to the strong mid-tropospheric flow N of Jamaica. If anything, I think the NHC and the models might be overdoing the intensity in the tropical stage of Sandy. My estimate is 50 kt for the maximum intensity in the Caribbean, as I think this system will have trouble developing an inner core over the next few days. (Wilma 2005, by contrast, faced much lower shear and higher instability for hundreds of miles in its vicinity.)

(As you can see, upon closer inspection, I have definitely revised my estimates from a few days ago... :( )

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Old image but has an okay curved band to the south. Looks better but still some dry air on the NW side.

Edit: the couple hot towers appear to be trying to orbit the center as oppose to training, not bombing, but the next recon should find a 995 pressure. I can't stand it when recons find nothing new.

20121022.2108.f15.x.85h_1deg.18LEIGHTEEN.25kts-1002mb-129N-788W.58pc.jpg

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The GEFS models through day 5 are in very strong agreement that ex-Sandy will miss the Southeast...note that the spread is relatively small well into 144 hours. The planetary wave pattern in recent weeks tends to favor the GEFS rather than the ECMWF evolution of the trough, thus supporting a slower and deeper shortwave impulse by day 4 and a less negatively tilted long-wave trough during and after day 5. This set-up makes the phasing of the ECMWF solution much less probable, and ex-Sandy much more likely to be substantially weaker than indicated. Since the trend in the ensemble mean has been farther east, I think the likelihood is increasing that ex-Sandy will be more of a Maritime Canadian than a New England threat. I also now believe that the pattern and general model consensus is strong enough to eliminate the threat to S FL, as ex-Sandy will most likely pass 100+ n mi off the east coast of the FL peninsula.

Link to GEFS spread

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00z SHIPS makes it a hurricane in 24 hours

Also

Prob of RI for 25 kt RI threshold= 67% is 5.3 times the sample mean(12.8%)

Prob of RI for 30 kt RI threshold= 64% is 7.6 times the sample mean( 8.4%)

Prob of RI for 35 kt RI threshold= 45% is 9.0 times the sample mean( 5.0%)

Prob of RI for 40 kt RI threshold= 29% is 8.4 times the sample mean( 3.4%)

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00z SHIPS makes it a hurricane in 24 hours

Also

Prob of RI for 25 kt RI threshold= 67% is 5.3 times the sample mean(12.8%)

Prob of RI for 30 kt RI threshold= 64% is 7.6 times the sample mean( 8.4%)

Prob of RI for 35 kt RI threshold= 45% is 9.0 times the sample mean( 5.0%)

Prob of RI for 40 kt RI threshold= 29% is 8.4 times the sample mean( 3.4%)

Lets see if it can develop an inner core to actually be able to do something with these numbers...

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i think this system stands a far greater chance than Isaac did. mutch more energy to work with.

Unfortunately there is a lack of wind on the NE side now. If winds increase to about 70mph (Wilma just before RI) it can realy capitalize on the tchp and start the rapid freefall to it's MPI.

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