ATL: OPHELIA - Remnants - Discussion

[Gustywind]

Once again the NE Caribbean is in the track of systems in 2011.

http://img838.imageshack.us/img838/7069 ... w5nlsm.gif

Hey hey, we have another one to monitor carefully

[tobol.7uno]

Intensity forecast is a good one, mine nearly matches it! It is not too uncertain either I suppose since the only factor effecting the intensity of the storm, and that is wind shear.

[Hylian Auree]

I don't agree with wind shear being the only limiting factor, maybe just the key factor. The region also supports low deep-layer instability, and the environment isn't moist enough to support significant intensification.

[HurricaneWarning92]

WOW, that track is practically the exact same thing as Maria's...

[HurricaneWarning92]

IMO, models still are not in agreement of a definite recurve away from any other land areas other than the Lesser Antilles...

[tobol.7uno]

I don't agree with wind shear being the only limiting factor, maybe just the key factor. The region also supports low deep-layer instability, and the environment isn't moist enough to support significant intensification.

The reason I say this is because it is not extremely dry air that seems to be getting more moist, and it is also well ahead of the center.

[FireRat]

Wow, that was quick!

Second time I remember seeing the "O" storm in September.

[cycloneye]

Wow, that was quick!

It took it's time to slowly organize as is Monsoon type.

[tobol.7uno]

Good Read...
000
WTNT41 KNHC 210300
TCDAT1

TROPICAL STORM OPHELIA DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL162011
1100 PM EDT TUE SEP 20 2011

THE LOW OVER THE TROPICAL ATLANTIC HAS FINALLY COALESCED ABOUT A
SINGLE CIRCULATION CENTER AND HAS ENOUGH ORGANIZED DEEP CONVECTION
TO BE CONSIDERED A TROPICAL CYCLONE. AN ASCAT PASS JUST BEFORE 00Z
SHOWED AN AREA OF 35 KT WINDS NORTH OF THE CENTER...AND THAT IS THE
INITIAL INTENSITY FOR THIS ADVISORY. THE SATELLITE PRESENTATION OF
OPHELIA IS STILL A LITTLE RAGGED...WITH CONVECTIVE BANDS LOCATED
WELL NORTHEAST AND SOUTH OF THE STILL CONSOLIDATING CENTER. WHILE
OPHELIA WILL BE MOVING OVER WARM WATERS THROUGH THE PERIOD...THE
SHEAR IS EXPECTED TO REMAIN AROUND 15 KT OR SO OVER THE NEXT COUPLE
OF DAYS. AFTER THAT TIME...THE SHEAR SHOULD INCREASE AND BECOME
MORE WESTERLY AS THE GLOBAL MODELS SHOW AN UPPER-LEVEL LOW FORMING
NORTH OF PUERTO RICO. GIVEN THE MARGINAL ENVIRONMENT AND THE
SOMEWHAT SPRAWLING NATURE OF THE CYCLONE AT THIS TIME...ONLY MODEST
STRENGTHENING IS SHOWN IN THE SHORT TERM. BEYOND 36 HOURS...LITTLE
CHANGE IN STRENGTH IS FORECAST...FOLLOWED BY WEAKENING LATE IN THE
PERIOD. THE NHC FORECAST IS NEAR OR A LITTLE ABOVE THE IVCN
INTENSITY CONSENSUS THROUGH THE PERIOD.

THE INITIAL MOTION ESTIMATE IS A RATHER UNCERTAIN 270/8...DUE TO THE
RECENT REFORMATION OF THE CENTER. OPHELIA IS CURRENTLY BEING
STEERED BY THE SUBTROPICAL RIDGE TO ITS NORTH...AND A WESTWARD
MOTION IS EXPECTED OVER THE NEXT COUPLE OF DAYS AS THE RIDGE BUILDS
WESTWARD. AFTER THAT TIME...THE RIDGE BEGINS TO WEAKEN AS A LARGE
MID/UPPER-LEVEL CLOSED LOW DEVELOPS OVER THE SOUTHEASTERN UNITED
STATES...WHICH SHOULD RESULT IN A TURN TOWARD THE WEST-NORTHWEST
AND A DECREASE IN FORWARD SPEED LATE IN THE PERIOD. THE NHC TRACK
FORECAST LIES TO THE RIGHT OF THE MULTI-MODEL CONSENSUS THROUGH THE
PERIOD...BUT IS A LITTLE TO THE LEFT OF THE GFS AND ECMWF MODELS.

FORECAST POSITIONS AND MAX WINDS

INIT 21/0300Z 12.2N 40.1W 35 KT 40 MPH
12H 21/1200Z 12.4N 42.2W 40 KT 45 MPH
24H 22/0000Z 12.7N 44.9W 45 KT 50 MPH
36H 22/1200Z 12.9N 47.7W 45 KT 50 MPH
48H 23/0000Z 13.2N 50.5W 45 KT 50 MPH
72H 24/0000Z 15.0N 55.5W 45 KT 50 MPH
96H 25/0000Z 17.0N 60.0W 40 KT 45 MPH
120H 26/0000Z 19.0N 64.0W 40 KT 45 MPH

$$
FORECASTER BRENNAN

[chrisjslucia]

Well the models seem to be covering all bases with Ophelia. Anything from the North of Trinidad to the wide open spaces to the North of Antigua. Far too open for us Looshans.

Why such a range? Is the centre yet to be pinned down? Whatever, we need some guidance as to timing, size and general direction - if such questions are answerable at this stage.

Any views on this?

[cycloneye]

Let's see how the distance gets closer or away from my house as each advisory comes in.

http://stormcarib.com/closest1.htm

Results for San Juan, Puerto Rico (18.45N, 66W):
The approximate Closest Point of Approach (CPA) is located near 19.0N, 64.0W or about 136.4 miles (219.5 km) from your location. This is corresponding with the 120 hour position of the 5-day forecast (Sunday, September 25 at 11:00PM EDT).

[tobol.7uno]

Let's see how the distance gets closer or away from my house as each advisory comes in.
Results for San Juan, Puerto Rico (18.45N, 66W):
The approximate Closest Point of Approach (CPA) is located near 19.0N, 64.0W or about 136.4 miles (219.5 km) from your location. This is corresponding with the 120 hour position of the 5-day forecast (Sunday, September 25 at 11:00PM EDT).

One bit of good news if that happens, it will be in radar range!

[djones65]

Just looking at the BAM models (I am not looking at track because they are not dynamical and will not include the downstream synoptics), but they seem to be closer together than previous runs. I learned a long while ago it is the "poor" mans rough estimate of shear... The closer the BAM Shallow, medium, and deep layers are obviously the less shear. So, at first glance only, in my humble opinion, the upper low forecast to develop north of the Greater Antilles may not exert quite as much shear as previously forecast... Either it will move in tandem perhaps at least for a little while until the upper trof over the Southeast stops it or it may be weaker and/or form farther north than previously forecast... Just a quick observation. Previously, the BAM's were incredibly far apart indicative of tremendous shear now it looks more moderate or slight in my opinion.

[AJC3]

Well the models seem to be covering all bases with Ophelia. Anything from the North of Trinidad to the wide open spaces to the North of Antigua. Far too open for us Looshans.

Why such a range? Is the centre yet to be pinned down? Whatever, we need some guidance as to timing, size and general direction - if such questions are answerable at this stage.

Any views on this?

Yep. The more reliable model guidance moves Ophelia near or north of the NE Caribbean, and so does the official forecast. Also, all the reliable global model guidance weakens the system once it gets near there, and *drum roll*...so does the official forecast. Looks quite reasonable to me.

[AJC3]

Just looking at the BAM models (I am not looking at track because they are not dynamical and will not include the downstream synoptics), but they seem to be closer together than previous runs. I learned a long while ago it is the "poor" mans rough estimate of shear... The closer the BAM Shallow, medium, and deep layers are obviously the less shear. So, at first glance only, in my humble opinion, the upper low forecast to develop north of the Greater Antilles may not exert quite as much shear as previously forecast... Either it will move in tandem perhaps at least for a little while until the upper trof over the Southeast stops it or it may be weaker and/or form farther north than previously forecast... Just a quick observation. Previously, the BAM's were incredibly far apart indicative of tremendous shear now it looks more moderate or slight in my opinion.

Well, actually they are still quite far apart between 36 and 96 hours, and only start to get a little closer toward day 5.

BAMS (0) 12.0N 39.6W (12) 12.7N 43.2W (24) 13.0N 47.2W (36) 12.6N 51.4W
BAMD (0) 12.0N 39.6W (12) 12.7N 41.8W (24) 13.6N 44.2W (36) 14.7N 46.5W

BAMS (48) 11.8N 54.9W (72) 10.6N 60.0W (96) 12.5N 62.8W (120) 16.4N 64.3W
BAMD (48) 15.9N 48.7W (72) 18.4N 52.5W (96) 20.8N 55.8W (120) 23.0N 59.4W

[tobol.7uno]

2am models...

[tobol.7uno]

GFS Ensemble...

[tobol.7uno]

Intensity, GFDx really went up on this run...

[tobol.7uno]

overall organization starting to pick up, microwave images looking better...

[Gustywind]

21/0545 UTC 12.5N 41.3W T2.5/2.5 OPHELIA
20/2345 UTC 12.5N 39.6W T2.0/2.0 98L