Hurricane Katia

[MJO812]

FWIW the experimental FIMY ENK at 156 hrs...Rest of the run still needs to come out....

For the fishes ( FIM )

[atownwxwatcher]

For the fishes

Anthony that is not the FIMY ENK ...

Only out thru 168 so far.....

[GaWx]

WEENIE ALERT! Not that I believe it or that it is an accurate model vs. the GFS/Euro, but FWIW (pure entertainment for the weenies) the 12Z JMA is about 300 miles west of yesterday's 12 run at hour 120 and is similar to the 12Z UKMET with it moving westward at ~ 10 mph into the SE Bahamas at 144 hours. However, even that has the look of something that would sharply recurve soon after that time and miss FL based on the upper air maps showing a persistent trough not too far west of there (see 2nd posted map). So, weenies, don't get too excited lol. Anyone with Accuwx could confirm that as it goes out to hour 192.

Fri 12Z JMA sfc at 144 hours:

Fri 12Z JMA 500 mb: note the deep trough in the E US

[TUweathermanDD]

Anthony that is not the FIMY ENK ...

Only out thru 168 so far.....

Thats because its the actual FIM, not the FIMYENK.

[LakeEffectKing]

Thats because its the actual FIM, not the FIMYENK.

It's a fish....by the length of a fish.... until it LF's in Nova Scotia

[phlwx]

New Euro turns it east quite far out. The Ukie's far south track is a super outlier, remember how wretchedly too far left it was with Irene. I still say this fishes out. Personally I am far more interested in Lee.

Lee will be the bigger story...Katia could be a nice surf event end of next week.

Am far more interested...and concerned with what Lee does in the Mid Atlantic.

[Shawn]

Does anyone know how well the JMA handles systems coming from the Tropics in general? It's pretty close to the UKMET and was wondering if it has the same sorta of "south & left" thing going on also historically? The JMA wasn't the worst model around the Winters of 2010/2011 for the Southeast on quite a few occasions.

[dan88]

Microwave looking somewhat decent, but struggling along the South and East sides.

[k***]

Does anyone know how well the JMA handles systems coming from the Tropics in general? It's pretty close to the UKMET and was wondering if it has the same sorta of "south & left" thing going on also historically? The JMA wasn't the worst model around the Winters of 2010/2011 for the Southeast on quite a few occasions.

It's pretty much useless...so much so that it isn't even scored vs the other models, included in any of the consensus tracks like the TVCN or TVCA, and rarely mentioned outside of random weenie posts here and there.

Microwave looking somewhat decent, but struggling along the South and East sides.

that's pretty good for a 65 kt storm.

[phil882]

that's pretty good for a 65 kt storm.

Yes. It looks like the shear moved through Katia a good 24-48 hours earlier than expected, which has thrown a giant monkey wrench in most people's forecasts including the NHC. The shear is already starting to subside around the storm and I think we should see conditions gradually improve over the next three days with slow development expected, perhaps a little bit faster in the short term in comparison to the NHC.

[LakeEffectKing]

You mean marla?

18z NoGaps shows either a LF or extremely close LF at Cape Hatteras, then threatens areas further north:

[k***]

question for the red taggers: how credible is the NOGAPS?

[Baroclinic Zone]

question for the red taggers: how credible is the NOGAPS?

I was reading that it runs on 4dvar data. assimilation. Not sure how that plays into it's model scores though.

[LakeEffectKing]

question for the red taggers: how credible is the NOGAPS?

Not sure what you mean by "credibility" but used as a tool, it has value....just like every other model....if you know how to use it (ie learn it's biases, tendencies)

[k***]

Not sure what you mean by "credibility" but used as a tool, it has value....just like every other model....if you know how to use it (ie learn it's biases, tendencies)

In a nutshell, what are its biases?

[TUweathermanDD]

In a nutshell, what are its biases?

To be honest, I've always been familiar with it as a progressive model with winter systems, does the same apply in tropical entities LEK?

[Scott747]

I believe that they dropped the NOGAPS from the TVCN and TCON for the 2011 season because the consensus models preformed much better when it was not used.

Still kept it for the EPAC as it apparently had a much better performance on that side.

[LakeEffectKing]

In a nutshell, what are its biases?

LOL! Since you've gained a reputation today as being a "met" killa....I'll pass...but thanks for the question....

[k***]

LOL! Since you've gained a reputation today as being a "met" killa....I'll pass...but thanks for the question....

Well maybe someone else can answer it, then. I'm just trying to figure out how to use it as guidance instead of just summarily dismissing it.

[Scott747]

Before the discussion deteriorates any further like earlier today, the specifics of models and such will be better served in a model thread for Katia if it were to indeed pose a real threat for the EC.

[SnowGoose69]

question for the red taggers: how credible is the NOGAPS?

It was damn good with Irene from 72-96 hours, I know that, it had the western track up into NYC with the initial landfall in NC right as well. It was not good though beyond that, as a matter of fact it was tending to be a bit too far south and west. The progressive bias from my experience generally does not apply with tropicals because you're dealing with system moving in the reverse direction.

[ORH_wxman]

It was damn good with Irene from 72-96 hours, I know that, it had the western track up into NYC with the initial landfall in NC right as well. It was not good though beyond that, as a matter of fact it was tending to be a bit too far south and west. The progressive bias from my experience generally does not apply with tropicals because you're dealing with system moving in the reverse direction.

It did do well with Irene. I will give it that. Overall though its degraded quite a bit in recent years though. I think back in the early 2000s, it actually scored pretty well with tropical systems in the Atlantic. But the model hasn't been improved much since then and other guidance has passed it.

[Amped]

000

WTNT42 KNHC 030254

TCDAT2

HURRICANE KATIA DISCUSSION NUMBER 20

NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011

1100 PM AST FRI SEP 02 2011

A SERIES OF MICROWAVE IMAGES DURING THE LATE AFTERNOON CLEARLY

SHOWED THE MID-LEVEL CENTER DISPLACED TO THE NORTH OF THE LOW-LEVEL

ONE. THIS MEANS THAT KATIA CONTINUES SUFFERING FROM SOUTHERLY SHEAR

AND HAS NOT INTENSIFIED. THE CLOUD PATTERN IS NOT VERY IMPRESSIVE

FOR A HURRICANE...BUT THE INITIAL INTENSITY IS CONSERVATIVELY KEPT

AT 65 KNOTS BASED ON T-NUMBERS FROM TAFB AND SAB. THERE IS A

SIGNIFICANT EXPANSION OF THE OUTFLOW IN THE WESTERN SEMICIRCLE

GIVING THE FALSE IMPRESSION THAT THE SHEAR IS WEAKENING. THIS IS

EXPECTED TO BE TRANSIENT SINCE WATER VAPOR IMAGES STILL SHOW THAT

THE UPPER-LEVEL TROUGH CAUSING THE SHEAR IS STILL THERE...AND

GLOBAL MODELS BASICALLY KEEP POSTPONING ITS WEAKENING. ACTUALLY...

THE SHIPS MODEL INDICATE THAT UPPER-LEVEL WIND ENVIRONMENT WILL

REMAIN HOSTILE FOR 24 TO 36 HOURS...WHILE THE ECMWF KEEPS IT

HOSTILE EVEN LONGER. ON THIS BASIS...THE OFFICIAL FORECAST CALLS

FOR NO CHANGE IN INTENSITY FOR ABOUT TWO DAYS AND FOR STRENGTHENING

THEREAFTER.

KATIA IS MOVING TOWARD THE NORTHWEST OR 305 DEGREES AT 10 KNOTS.

GLOBAL MODELS UNANIMOUSLY BUILD THE SUBTROPICAL RIDGE WESTWARD AND

WEAKEN THE TROUGH OVER THE WESTERN ATLANTIC. THIS FORECAST PATTERN

CALLS FOR A GENERAL NORTHWEST TO WEST-NORTHWEST TRACK WITH NO

SIGNIFICANT CHANGE IN SPEED THROUGH FIVE DAYS AS INDICATED IN THE

NHC FORECAST. WITH THE EXCEPTION OF THE UK MODEL WHICH BUILDS A

STRONGER SUBTROPICAL RIDGE THAN THE OTHER MODELS AND KEEPS KATIA ON

A MORE WESTWARD TRACK...THE REST OF THE TRACK MODELS ARE IN GOOD

AGREEMENT. THE OFFICIAL FORECAST IS IN THE MIDDLE OF THE GUIDANCE

ENVELOPE AND IS VERY CLOSE TO THE ECMWF AND THE GFS GLOBAL MODELS.

FORECAST POSITIONS AND MAX WINDS

INIT 03/0300Z 18.5N 54.3W 65 KT 75 MPH

12H 03/1200Z 19.5N 55.4W 65 KT 75 MPH

24H 04/0000Z 20.5N 57.0W 65 KT 75 MPH

36H 04/1200Z 21.5N 59.0W 65 KT 75 MPH

48H 05/0000Z 22.5N 60.5W 75 KT 85 MPH

72H 06/0000Z 24.5N 63.5W 85 KT 100 MPH

96H 07/0000Z 26.5N 66.5W 95 KT 110 MPH

120H 08/0000Z 28.0N 69.5W 95 KT 110 MPH

$$

FORECASTER AVILA

HAha

[phil882]

HAha

Always fun to watch the subjectivity on display between the different forecasters. You can always count on Stewart to be pretty bullish, while Avila is normally pretty conservative.

[Amped]

Always fun to watch the subjectivity on display between the different forecasters. You can always count on Stewart to be pretty bullish, while Avila is normally pretty conservative.

You can tell they were either reading this thread or arguing about the topic themselves earlier. Their net forecasts aren't much different though.

[SnowGoose69]

It did do well with Irene. I will give it that. Overall though its degraded quite a bit in recent years though. I think back in the early 2000s, it actually scored pretty well with tropical systems in the Atlantic. But the model hasn't been improved much since then and other guidance has passed it.

I'm not sure this effects it during tropical season but last winter I thought of the possibility since its a progressive model it performs poorly during La Ninas because its bias is enhanced. Tony from Mt. Holly then said ironically the 97-98 winter was probably the best performance the NOGAPS had during a strong El Nino where its normal bias would be canceled out somewhat.. I do think it performed well on Isabel but like you said I've noticed it misses more tropicals than it gets right.

Speaking of using typical model biases and getting a sense when they may be right vs. the other models....notice the 00z hurricane models show the BAMM set being on the western edge of the guidance....given the BAMM typically performs the worst that should tip most of us off that right now the recurvature is the way to go.

[donsutherland1]

At 11 pm, Katia was centered at 18.5°N 54.3°W. Its 6-hour motion was 276°. Its 12-hour motion was 294°. In response to a track that is somewhat to the south of most of the guidance, the NHC has made modest adjustments to the left in recent forecasts. Examples for NHC forecasts at 20°N and 25°N follow for the 9/2 11 am, 5 pm, and 11 pm forecasts:

20°N: 55.7°W, 55.9°W, 56.2°W

25°N: 62.5°W, 63.5°W, 64.5°W

Given Katia's current track and the reasonable stability in the global guidance (preferences for a blend of the ECMWF, ECMWF ensembles, GFS, and GFS ensembles), I believe my first guess concerning Katia's track remains reasonably on course. If anything, the early part of the course might wind up being somewhat to the east of Katia's track, as a trajectory of 297° would be needed to get to my estimated position at 20N and 300° for my estimated position at 25N.

17.5N 52.8W; Actual: 17.5N 52.4; Error: 26 miles--1.5 hours in advance

20.0N 56.8W

25.0N 63.9W

30.0N 72.0W

35.0N 69.6W

40.0N 63.5W

Given the 12z ECMWF/ECMWF ensembles and the 18z GFS/GFS ensembles, I still expect that Katia will get as far west as 72W-74W. However, the longer it takes a more westerly course, the greater the prospect will be that Katia might not be able to turn sharply enough to avoid U.S. landfall. For now, I suspect such landfall is about a 1-in-3 prospect, with recurvature away from the East Coast remaining the most likely outcome. Nevertheless, some of Katia's rains could impact eastern North Carolina and possibly Nantucket and Cape Cod, especially if the storm passes closer than what I have outlined above.

Finally, although Katia remains a Category 1 hurricane after having briefly lost hurricane status, I still believe prospects are good for Katia's eventually attaining major hurricane status. One of my two favored analog storms (Gladys in 1975), reached hurricane status at 44.0W (vs. Katia's 44.4W). Its pressure then rose from 990 mb to 1000 mb at 58.2W, even as its windspeed remained 75 mph. Afterward slow intensification commenced. Gladys became a Category 3 storm at 31N 73W and then peaked as a Category 4 hurricane at 35.3N 69.8W. Interestingly enough, the 9/2 12z run of the ECMWF forecasts Katia to have a central pressure of 936 mb at 192 hours in a position just south of where Gladys peaked. A 936 mb hurricane would imply a storm at the upper bound of Category 3 or even Category 4.

Intensity forecasting remains challenging and model errors at 3-5 days out can be large. Given historic climatology with storms that formed in the region in which Katia developed and took tracks reasonably similar to Katia's generally becoming very powerful, though sometimes after slow or erratic development, I remain confident that Katia will eventually become a major hurricane and probably peak at Category 4 strength.

[Cheeznado]

Euro is not good for landfall wishers so far, farther NE at 96 hours, trough associated with Lee faster. A fish for sure it looks like, will post later times in a bit.

UPDATE: Euro closer to Bermuda than the US.

[k***]

odd microwave shot, even for a sheared system

[wxmx]

mid and low levels are not vertically aligned

odd microwave shot, even for a sheared system