ATL: KATIA - Post Tropical - Discussion

[bahamaswx]

After Ike I'll never trust a fish to stay a fish.

[geomindspin]

Sorry to be the noob, I have been reading and checking these forums for a year or two now, but rarely post. I never understood what 12z or 18z, etc represent in reference to model runs. I'm still learning this. Can someone help? Thanks!

[Aric Dunn]

Eyewall on its way... is likely a hurricane ..

[DESTRUCTION5]

Sorry to be the noob, I have been reading and checking these forums for a year or two now, but rarely post. I never understood what 12z or 18z, etc represent in reference to model runs. I'm still learning this. Can someone help? Thanks!

Since your in Ft Lauderdale 00Z is midnight/06Z 6am/12Z noon/18z 6pm or approx of the time them model runs come out..

[gtalum]

12z, 18z, etc represent the time the model is initialized. z stands for zulu, the same as Greenwich Mean Time (GMT). Subtract 4 hours for EDT.

[KWT]

I'd go with 60kts myself Aric, but its steadily getting there now from the looks of things...

[boiker]

I'd go with 60kts myself Aric, but its steadily getting there now from the looks of things...

Agreed. It looks like Katia has finally gotten herself well-organized. She's ready to deepen now.

[Jevo]

Current Steering



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[Blown Away]

BigJoeBastardi Joe Bastardi
Still not convinced Katia stays out a sea-a. Slew of models like my idea of further west (ensembles, plus Canadian)

From Joe Bastardi's twitter, I still think it's funny following weather on twitter.

[WeatherLovingDoc]

^^^ Regarding the wind map WxGuy posted above:

"Here's the 250 mb map (which is about 30,000 feet above sea level) valid at the end of next week. Katia, in this run, is located on the far right part of the image. This trough is forecast to move eastward into the western Atlantic, causing Katia to move NNW and eventually lose tropical characteristics:"

Is the "trough" the blue/pink wind area east of the US coast line? Is it a low pressure area? I am really struggling with visiably seeing what is a trough and ridge (as I posted elsewhere). Thanks.

[DESTRUCTION5]

BigJoeBastardi Joe Bastardi
Still not convinced Katia stays out a sea-a. Slew of models like my idea of further west (ensembles, plus Canadian)

From Joe Bastardi's twitter, I still think it's funny following weather on twitter.

He still left the door open there though.....Confidence dont sound like it did 3 days ago with the telconnection tweets...

[cycloneye]

TROPICAL STORM KATIA DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
500 PM AST WED AUG 31 2011

KATIA IS NEAR THE THRESHOLD OF HURRICANE STATUS. THE SYSTEM
CONTINUES TO EXHIBIT PROMINENT CURVED CONVECTIVE BANDS AND DEEP
CONVECTION IS BECOMING STRONGER OVER THE CENTER. THE STORM ALSO
HAS A FAIRLY SYMMETRIC AND WELL-ESTABLISHED UPPER-LEVEL OUTFLOW
PATTERN. DVORAK INTENSITY ESTIMATES FROM BOTH AGENCIES REMAIN AT
55 KT...BUT AMSU INTENSITY ESTIMATES FROM THE UNIVERSITY OF
WISCONSIN CIMSS ARE A LITTLE HIGHER. THE INTENSITY IS SET AT 60 KT
FOR THIS ADVISORY. WEAK VERTICAL SHEAR AND MODESTLY WARM WATERS
ARE LIKELY TO PREVAIL OVER THE NEXT FEW DAYS...SO CONTINUED
INTENSIFICATION IS FORECAST. A LARGE UPPER-LEVEL LOW TO THE
NORTHWEST OF KATIA COULD CAUSE AN INCREASE IN SHEAR...AND INHIBIT
INTENSIFICATION...LATE IN THE FORECAST PERIOD. HOWEVER SOME OF THE
GLOBAL MODELS...SUCH AS THE GFS...SUGGEST THAT THE OUTFLOW
ANTICYCLONE OF KATIA WILL DOMINATE THE UPPER-LEVEL WIND PATTERN AND
DISPLACE THE SHEARING FLOW ASSOCIATED WITH THE LOW. IF THAT
OCCURS...KATIA WOULD LIKELY BECOME A MAJOR HURRICANE BY DAY 4 OR 5.
THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE AND
SLIGHTLY HIGHER THAN THE STATISTICAL-DYNAMICAL GUIDANCE.

THE STORM CONTINUES TO MOVE WEST-NORTHWESTWARD ON THE SOUTH SIDE OF
A SUBTROPICAL ANTICYCLONE. THE TRACK FORECAST AND REASONING ARE
ESSENTIALLY UNCHANGED. AS KATIA NEARS THE SOUTHWEST SIDE OF THE
ANTICYCLONE...A GRADUAL TURN TOWARD THE NORTHWEST WITH DECREASING
FORWARD SPEED IS LIKELY. THE CURRENT OFFICIAL TRACK FORECAST IS AN
UPDATE OF THE PREVIOUS ONE AND ABOUT IN THE MIDDLE OF THE GUIDANCE
ENVELOPE. IT IS ALSO A LITTLE TO THE WEST OF THE GFS AND ECMWF
SOLUTIONS.

FORECAST POSITIONS AND MAX WINDS

INIT 31/2100Z 14.6N 42.6W 60 KT 70 MPH
12H 01/0600Z 15.1N 44.9W 65 KT 75 MPH
24H 01/1800Z 15.8N 47.7W 75 KT 85 MPH
36H 02/0600Z 16.6N 50.0W 85 KT 100 MPH
48H 02/1800Z 17.7N 52.0W 90 KT 105 MPH
72H 03/1800Z 20.0N 55.5W 95 KT 110 MPH
96H 04/1800Z 22.0N 58.5W 100 KT 115 MPH
120H 05/1800Z 23.5N 61.0W 105 KT 120 MPH

$$
FORECASTER PASCH

[gatorcane]

looks like about a 280 movement to me, not really gaining a whole lot of lattitude and racing westwards.

You have to think the NHC will mention something about the models on this discussion, how some are trending west and building a ridge to the north, especially when the ECMWF makes a big west shift on its thinking.

[WeatherLovingDoc]

Current Steering

[img]http://40.imageshack.us/img40/3403/wg8dlm2.gif[/

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Jevo, can you explain what a newbie might need to recognize on the current stearing and Katia? Thank you very much.

[cycloneye]

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...14.6N 42.6W
ABOUT 1285 MI...2070 KM E OF THE LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 20 MPH...32 KM/H
MINIMUM CENTRAL PRESSURE...990 MB...29.23 INCHES



Saved image.

[Aric Dunn]

yeah they are not going to mention the models shifting because most of them are past their 5 day forecast.. in the models continue to trend west than then come tomorrow the turn will be within the 5 days.

[gatorcane]

yeah they are not going to mention the models shifting because most of them are past their 5 day forecast.. in the models continue to trend west than then come tomorrow the turn will be within the 5 days.

Yeah good point....

[Blown Away]

yeah they are not going to mention the models shifting because most of them are past their 5 day forecast.. in the models continue to trend west than then come tomorrow the turn will be within the 5 days.

Yeah good point....

Also, the 11am & 5pm 5 day position is the same point, so that tells me there is some uncertainty and will wait for a few more W trending models runs and then maybe make a W shift in the 4-5 day track.

[HenkL]

If you are looking for ridges and troughs that can steer a hurricane, forget the maps with SLP.
Some forecast maps of today are very good examples of situations that can easily mislead us: showing a 'mighty' high pressure area at sea level, while at the same time there is no ridge at all at higher levels.

You have to look further up in the atmosphere: maps at 500 hPa and 250 hPa. Those maps don't show isobars (it's all 500 mb or 250 mb), but isoheights, lines with the same height of the pressure level (in dam, decameter = 10 meter). Higher numbers mean a thicker atmosphere (upper level high, ridge), lower numbers a thinner atmosphere (upper level low, trough).

(the colors in the WxGuy1 map are windspeeds)

[Wthrman13]

Sorry to be the noob, I have been reading and checking these forums for a year or two now, but rarely post. I never understood what 12z or 18z, etc represent in reference to model runs. I'm still learning this. Can someone help? Thanks!

Those are the times that the model is *initialized* (not necessarily run). That is, it's the valid time of the initial analysis of the atmosphere that goes into the model. So, a 12Z model run would have its initial conditions be a "snapshot" of what the atmosphere looked like at 12Z (or UTC), which is 8 a.m. EDT. Then, the model takes this snapshot and runs forward in time, producing forecasts out to several days. It takes time for the model to run on the computer and to produce all the output which is translated into webpage graphics and other derived products, so you don't normally see the 12Z run output until late in the morning or early afternoon, depending on the model.