Ex Tropical Depression KAREN: Discussions & Images

[Andy_L]

WHXX04 KWBC 251121
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER

NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR

TROPICAL DEPRESSION TWELVE 12L

INITIAL TIME 6Z SEP 25

DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT
REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD
NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC
OFFICIAL FORECAST.


FORECAST STORM POSITION

HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)

0 10.4 37.6 285./14.0
6 10.5 38.5 275./ 8.6
12 10.9 39.9 286./14.5
18 11.2 41.2 283./13.3
24 11.6 42.9 281./16.4
30 11.9 44.5 283./16.8
36 12.3 46.2 282./16.5
42 12.8 47.1 299./10.4
48 13.4 48.3 297./13.5
54 14.2 49.6 300./14.1
60 15.0 50.4 316./11.2
66 15.5 50.8 325./ 6.7
72 16.2 51.2 324./ 8.0
78 17.0 51.7 331./ 9.4
84 18.0 52.0 342./10.1
90 18.9 52.3 340./ 9.6
96 19.8 52.7 337./ 9.7
102 20.7 53.1 336./ 9.3
108 21.6 53.4 341./10.4
114 22.5 53.7 343./ 8.5
120 23.2 54.1 331./ 8.2
126 24.0 54.2 350./ 8.3

yikes.....UKMET isn't looking very fishy from the graphic above....what are the chances of that verifying???

[bvigal]

25/1145 UTC 10.6N 37.7W T2.5/2.5 KAREN

p.s. Can someone update the thread title? This is Central Atlantic now.

[jasons2k]

From Jeff Lindner:

Tropical Storm Karen forms in the C ATL Ocean about 1500 miles E of the Windward Islands.

Discussion:

IR and visible images reveal a large tropical system with well defined banding features and deep convection near the center. Karen appears to be one of the largest and well defined Cape Verde storms of the 2007 season.

Track:

Model guidance is in fair agreement on a track toward the WNW for the next 72 hours as Karen is embedded on the south side of strong low to mid level ridging over the central ATL. After 72 hours a strong trough of low pressure is expected to develop NE of the Leeward Islands resulting in Karen turning to the NW and N into the weakness in the ridge. NHC is going to the south early and to the west later of the guidance clustering due to the biases in the guidance of turning recuvring storms over the tropical ATL too fast. However, Karen should safely recurve east of the Islands.

Intensity:

Unlike Dean and Felix, Karen is a very large storm with wide circulation field, hence time will be needed for consolidation of the inner core. Upper air outflow is slightly restricted on the western side, but overall the pattern favors intensification. All of the global guidance brings Karen to near hurricane intensity in 60 hours before the onset of strong wind shear associated with the mid ATL trough. If the inner core consolidates faster Karen could be much stronger.

[drezee]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 25 SEP 2007 Time : 134500 UTC
Lat : 10:35:32 N Lon : 39:07:49 W


CI# /Pressure/ Vmax
2.7 /1003.0mb/ 39.0kt


6hr-Avg T# 3hr-Avg T# Adj T# Raw T#
2.7 2.7 2.9 3.5

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -17.3C Cloud Region Temp : -45.5C

Scene Type : CURVED BAND with 0.75 ARC in MD GRAY
Maximum CURVED BAND with 0.84 ARC in MD GRAY
at Lat: 10:35:24 N Lon: 39:43:47 W

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.7T/6hr
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

[hurricanetrack]

Looks like Karen will open a large door for any future development off of Africa to slip through and out in to the north Atlantic. As per a conversation I had with Mike Watkins this morning, it will be difficult for even a tropical wave to get past the chasm that will open in the central Atlantic over the next week to 10 days or more.

We have been very lucky this year that the ridge was either too strong and kept the killers to the south or will be non-existent now with these late Cape Verde bloomers coming.

[Sanibel]

Karen is still at 38W and well east but looks pocked with dry air and having strength issues for now. I'm not saying it will fail like Ingrid, just that it isn't deep and robust right now. Was at 9N last night and is now well above 10N. I would say it would be reasonable to say we are safe here in Florida.

[HURAKAN]

344
WTNT42 KNHC 251433
TCDAT2
TROPICAL STORM KAREN DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007
1100 AM EDT TUE SEP 25 2007

KAREN IS EXHIBITING SOME BANDING FEATURES ON VISIBLE SATELLITE
IMAGERY BUT THE DEEP CONVECTION IS NOT THAT STRONG OR CONCENTRATED
NEAR THE CENTER AT THIS TIME. DVORAK INTENSITY ESTIMATES FROM TAFB
AND SAB REMAIN AT 35 KT SO THE CURRENT INTENSITY IS UNCHANGED FROM
THE PREVIOUS ADVISORY. THE ENVIRONMENT AHEAD OF THE STORM IS
QUESTIONABLE FOR STRENGTHENING. KAREN'S UPPER-LEVEL OUTFLOW IS
BEING RESTRICTED OVER THE NORTHWEST QUADRANT DUE TO A NEARBY
UPPER-LEVEL CYCLONIC SHEAR AXIS. WITHIN THE NEXT FEW DAYS...
GLOBAL MODELS DEPICT A COUPLE OF UPPER-LEVEL TROUGHS OVER THE
CENTRAL SUBTROPICAL ATLANTIC THAT SHOULD CAUSE INCREASING
SOUTHWESTERLY VERTICAL SHEAR OVER THE TROPICAL CYCLONE. THE SHIPS
MODEL...USING THE GFS FORECAST...SHOWS THE SHEAR INCREASING TO 20 KT
BY 60 HOURS AND MORE THAN 30 KT NEAR THE END OF THE PERIOD. IN
SPITE OF THIS SEEMINGLY HOSTILE ENVIRONMENT...SHIPS PREDICTS KAREN
TO BECOME A HURRICANE BY 48 HOURS AND TO MAINTAIN HURRICANE
STRENGTH ALMOST TO THE END OF THE FORECAST PERIOD. THE LATEST RUN
OF THE GFDL MODEL ALSO INTENSIFIES THE TROPICAL STORM INTO A
HURRICANE AFTER 72 HOURS. IT IS DIFFICULT TO ACCEPT THIS GUIDANCE
IN THE FACE OF SUCH STRONG PREDICTED SHEAR. THEREFORE THE OFFICIAL
FORECAST...AS IN THE PREVIOUS PACKAGE...STRENGTHENS KAREN TO JUST
BELOW HURRICANE STATUS AND THEN INDICATES WEAKENING AFTER DAY 3.

INITIAL MOTION...290/13 THE SAME AS IN THE PREVIOUS ADVISORY. KAREN
CONTINUES ON THE SOUTH SIDE OF A LOW- TO MID-LEVEL SUBTROPICAL
RIDGE. THIS SCENARIO SHOULD PERSIST FOR THE NEXT DAY OR SO.
AFTERWARDS...A MID- TO UPPER-TROPOSPHERIC CYCLONE SHOULD CREATE A
WEAKNESS IN THE RIDGE. IF THIS OCCURS...KAREN SHOULD GRADUALLY
TURN NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD. THERE CONTINUES
TO BE A FAIR AMOUNT OF SPREAD IN THE TRACK GUIDANCE MODELS. THE
HWRF AND GFS TRACKS ARE NEAR THE RIGHT SIDE OF THE GUIDANCE
ENVELOPE AND THE U.K. MET MODEL TRACK IS NEAR THE LEFT SIDE. THE
OFFICIAL FORECAST IS CLOSE TO THE DYNAMICAL CONSENSUS...NOT FAR
FROM THE GFDL TRACK...AND FAIRLY SIMILAR TO THE PREVIOUS NHC TRACK.

FORECAST POSITIONS AND MAX WINDS

INITIAL 25/1500Z 10.8N 38.7W 35 KT
12HR VT 26/0000Z 11.2N 40.7W 40 KT
24HR VT 26/1200Z 11.8N 43.5W 45 KT
36HR VT 27/0000Z 12.5N 46.1W 55 KT
48HR VT 27/1200Z 13.9N 48.3W 60 KT
72HR VT 28/1200Z 17.2N 51.2W 60 KT
96HR VT 29/1200Z 20.0N 53.0W 55 KT
120HR VT 30/1200Z 22.5N 54.0W 55 KT

$$
FORECASTER PASCH


814
WTNT32 KNHC 251432
TCPAT2
BULLETIN
TROPICAL STORM KAREN ADVISORY NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007
1100 AM AST TUE SEP 25 2007

...KAREN MOVING WEST-NORTHWESTWARD...NO IMMEDIATE THREAT TO LAND...

AT 1100 AM AST...1500Z...THE CENTER OF TROPICAL STORM KAREN WAS
LOCATED NEAR LATITUDE 10.8 NORTH...LONGITUDE 38.7 WEST OR ABOUT 1515
MILES...2440 KM...EAST OF THE WINDWARD ISLANDS.

KAREN IS MOVING TOWARD THE WEST-NORTHWEST NEAR 15 MPH...24 KM/HR...
AND THIS MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/HR...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM
FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB...29.68 INCHES.

REPEATING THE 1100 AM AST POSITION...10.8 N...38.7 W. MOVEMENT
TOWARD...WEST-NORTHWEST NEAR 15 MPH. MAXIMUM SUSTAINED WINDS...40
MPH. MINIMUM CENTRAL PRESSURE...1005 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
500 PM AST.

$$
FORECASTER PASCH

[vegastar]

TROPICAL STORM KAREN DISCUSSION NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122007
1100 AM EDT TUE SEP 25 2007

KAREN IS EXHIBITING SOME BANDING FEATURES ON VISIBLE SATELLITE
IMAGERY BUT THE DEEP CONVECTION IS NOT THAT STRONG OR CONCENTRATED
NEAR THE CENTER AT THIS TIME. DVORAK INTENSITY ESTIMATES FROM TAFB
AND SAB REMAIN AT 35 KT SO THE CURRENT INTENSITY IS UNCHANGED FROM
THE PREVIOUS ADVISORY. THE ENVIRONMENT AHEAD OF THE STORM IS
QUESTIONABLE FOR STRENGTHENING. KAREN'S UPPER-LEVEL OUTFLOW IS
BEING RESTRICTED OVER THE NORTHWEST QUADRANT DUE TO A NEARBY
UPPER-LEVEL CYCLONIC SHEAR AXIS. WITHIN THE NEXT FEW DAYS...
GLOBAL MODELS DEPICT A COUPLE OF UPPER-LEVEL TROUGHS OVER THE
CENTRAL SUBTROPICAL ATLANTIC THAT SHOULD CAUSE INCREASING
SOUTHWESTERLY VERTICAL SHEAR OVER THE TROPICAL CYCLONE. THE SHIPS
MODEL...USING THE GFS FORECAST...SHOWS THE SHEAR INCREASING TO 20 KT
BY 60 HOURS AND MORE THAN 30 KT NEAR THE END OF THE PERIOD. IN
SPITE OF THIS SEEMINGLY HOSTILE ENVIRONMENT...SHIPS PREDICTS KAREN
TO BECOME A HURRICANE BY 48 HOURS AND TO MAINTAIN HURRICANE
STRENGTH ALMOST TO THE END OF THE FORECAST PERIOD. THE LATEST RUN
OF THE GFDL MODEL ALSO INTENSIFIES THE TROPICAL STORM INTO A
HURRICANE AFTER 72 HOURS. IT IS DIFFICULT TO ACCEPT THIS GUIDANCE
IN THE FACE OF SUCH STRONG PREDICTED SHEAR. THEREFORE THE OFFICIAL
FORECAST...AS IN THE PREVIOUS PACKAGE...STRENGTHENS KAREN TO JUST
BELOW HURRICANE STATUS AND THEN INDICATES WEAKENING AFTER DAY 3.

INITIAL MOTION...290/13 THE SAME AS IN THE PREVIOUS ADVISORY. KAREN
CONTINUES ON THE SOUTH SIDE OF A LOW- TO MID-LEVEL SUBTROPICAL
RIDGE. THIS SCENARIO SHOULD PERSIST FOR THE NEXT DAY OR SO.
AFTERWARDS...A MID- TO UPPER-TROPOSPHERIC CYCLONE SHOULD CREATE A
WEAKNESS IN THE RIDGE. IF THIS OCCURS...KAREN SHOULD GRADUALLY
TURN NORTHWESTWARD AND THEN NORTH-NORTHWESTWARD. THERE CONTINUES
TO BE A FAIR AMOUNT OF SPREAD IN THE TRACK GUIDANCE MODELS. THE
HWRF AND GFS TRACKS ARE NEAR THE RIGHT SIDE OF THE GUIDANCE
ENVELOPE AND THE U.K. MET MODEL TRACK IS NEAR THE LEFT SIDE. THE
OFFICIAL FORECAST IS CLOSE TO THE DYNAMICAL CONSENSUS...NOT FAR
FROM THE GFDL TRACK...AND FAIRLY SIMILAR TO THE PREVIOUS NHC TRACK.

FORECAST POSITIONS AND MAX WINDS

INITIAL 25/1500Z 10.8N 38.7W 35 KT
12HR VT 26/0000Z 11.2N 40.7W 40 KT
24HR VT 26/1200Z 11.8N 43.5W 45 KT
36HR VT 27/0000Z 12.5N 46.1W 55 KT
48HR VT 27/1200Z 13.9N 48.3W 60 KT
72HR VT 28/1200Z 17.2N 51.2W 60 KT
96HR VT 29/1200Z 20.0N 53.0W 55 KT
120HR VT 30/1200Z 22.5N 54.0W 55 KT

$$
FORECASTER PASCH

[KWT]

Interesitng that the NHC are forecasting the shear to be as high as they are forecasting, esp given the way the models are bringing it upto hurricane status, something probably doesn't add up if the shear is as strong as the NHC claim it is going to be.

Dry air looks to be a little bit of an issue but I think given its size it may not be as large an issue as if we had a small system. Looks like we have banding and so winds may be upped to 40kts next advisory based on the higher sat.estimates.

[WindRunner]

Interesitng that the NHC are forecasting the shear to be as high as they are forecasting, esp given the way the models are bringing it upto hurricane status, something probably doesn't add up if the shear is as strong as the NHC claim it is going to be.

Dry air looks to be a little bit of an issue but I think given its size it may not be as large an issue as if we had a small system. Looks like we have banding and so winds may be upped to 40kts next advisory based on the higher sat.estimates.

You should be asking yourself the reverse . . . the NHC is looking at the models, which show both increasing shear and moderate strengthening for the storm. They've decided that, in looking at the shear forecasts, the models are underplaying the role of the shear, and have hence adjusted the intensities of the models downward.

Basically, don't take the models over the NHC . . . especially when your choice is are the models being insane or the NHC being insane. I know who I'd take . . .

[Lowpressure]

Interesitng that the NHC are forecasting the shear to be as high as they are forecasting, esp given the way the models are bringing it upto hurricane status, something probably doesn't add up if the shear is as strong as the NHC claim it is going to be.

Dry air looks to be a little bit of an issue but I think given its size it may not be as large an issue as if we had a small system. Looks like we have banding and so winds may be upped to 40kts next advisory based on the higher sat.estimates.

You should be asking yourself the reverse . . . the NHC is looking at the models, which show both increasing shear and moderate strengthening for the storm. They've decided that, in looking at the shear forecasts, the models are underplaying the role of the shear, and have hence adjusted the intensities of the models downward.

Basically, don't take the models over the NHC . . . especially when your choice is are the models being insane or the NHC being insane. I know who I'd take . . .

But aren't shear forecasts and predictions pretty unreliable? What has more credibility, a shear forecast or a model? I am asking, I do not know how good the shear forecasts are, I know about models.

[cpdaman]

for what it's worth TWC tropical update has been calling for development to be CAPPED at minimum hurricance intensity as well as recurve.

intresting that this may lay the foundation for more fishy's to follow it's wide tracks.

so looks like caribean develoment may be the last bullet we will need to dodge in OCT. assuming nothing comes from 97L

[CrazyC83]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 25 SEP 2007 Time : 161500 UTC
Lat : 10:52:24 N Lon : 38:59:12 W


CI# /Pressure/ Vmax
2.8 /1002.0mb/ 41.0kt


6hr-Avg T# 3hr-Avg T# Adj T# Raw T#
2.8 2.9 3.0 3.0

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -37.0C Cloud Region Temp : -39.7C

Scene Type : CURVED BAND with 0.54 ARC in MD GRAY
Maximum CURVED BAND with 0.80 ARC in MD GRAY
at Lat: 10:40:12 N Lon: 39:34:48 W

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

[WindRunner]

Interesitng that the NHC are forecasting the shear to be as high as they are forecasting, esp given the way the models are bringing it upto hurricane status, something probably doesn't add up if the shear is as strong as the NHC claim it is going to be.

Dry air looks to be a little bit of an issue but I think given its size it may not be as large an issue as if we had a small system. Looks like we have banding and so winds may be upped to 40kts next advisory based on the higher sat.estimates.

You should be asking yourself the reverse . . . the NHC is looking at the models, which show both increasing shear and moderate strengthening for the storm. They've decided that, in looking at the shear forecasts, the models are underplaying the role of the shear, and have hence adjusted the intensities of the models downward.

Basically, don't take the models over the NHC . . . especially when your choice is are the models being insane or the NHC being insane. I know who I'd take . . .

But aren't shear forecasts and predictions pretty unreliable? What has more credibility, a shear forecast or a model? I am asking, I do not know how good the shear forecasts are, I know about models.

The shear forecasts they refer to are coming from the very same models that you refer to. The more detailed bulletin of the SHIPS forecast includes shear strength, which is where they are getting the numbers from . . .

And yes, shear forecasts are less reliable than the models' track forecasts, but they are better than most of our intensity forecasting. Usually if anything is wrong with the shear forecasts, it'll be because of some relatively obvious error in the model's synoptics . . .

[cycloneye]

The Latest at 16:45 UTC

[Meso]

Noticed that the 12z run of the GFS has quite a strong ridge in place for a while

[Lowpressure]

Thanks for shear clarification WINDRUNNER.
Chuck

[Meso]

The 12z CMC looks further south than previous runs too.. Making it to the islands before turning north.

[dixiebreeze]

I don't think it's a given that Karen will be a fish -- not by a long shot.

[Gustywind]

I don't think it's a given that Karen will be a fish -- not by a long shot.

Yeah man... fish or not something to watch... !