Major Hurricane Katia

[Iceberg]

Recon have finished the first pass sw to ne the ne quad contains a ver large swabs of 100kt ft winds peaking at 114kt which would make her 95 100kts cat 3 these winds were quite away from the low pressure readings. In all I would say that without stronger winds nearer the centre there probably isn't an inner eye wall

Further passes should confirm this also the vortex will be intemresting

Sorry done on my phone and no additional info

[Paranoid]

The latest visible image seems to show an eye re-emerging. Nothing on IR images though so the eye probably only exists at upper and mid levels.

[Iceberg]

Recon have made 2 passes but cannot find any kind of eye structure, due to this she seems to be losing pressure approx 960mb but winds are still pretty high.

She might a chance to get herself together......

A. 06/18:39:40ZB. 27 deg 27 min N 066 deg 21 min WC. 700 mb 2759 mD. 81 ktE. 303 deg 44 nmF. 053 deg 91 ktG. 304 deg 53 nmH. 962 mbI. 9 C / 3044 mJ. 16 C / 3050 mK. NA / NAL. NAM. NAN. 12345 / 7O. 0.02 / 1 nmP. AF304 0112A KATIA OB 09MAX FL WIND 114 KT NE QUAD 17:11:00ZMAX OUTBOUND FL WIND 97 KT SE QUAD 18:54:30ZMAX FL TEMP 17 C 297 / 16 NM FROM FL CNTR

[picog]

The latest NHC discussion confirms the eyewall replacement and subsequent expansion of wind radii (this in turn making gradual changes in intensity more likely):

BY DAYS 4 AND 5...BAROCLINIC FORCING SHOULD PREVENT KATIA

FROM WEAKENING TOO MUCH...EVEN OVER COLDER WATERS...AND THE CYCLONE

IS FORECAST TO BE A POWERFUL EXTRATROPICAL STORM OVER THE NORTH

ATLANTIC. THE INTENSITY GUIDANCE IS IN FAIRLY GOOD AGREEMENT...AND

THE OFFICIAL FORECAST IS MAINLY JUST AN UPDATE OF THE PREVIOUS

FORECAST."

http://www.nhc.noaa....l/061445.shtml?

That sounds like she could be headed towards the UK, still with high winds and lots of rain?

[Liam J]

She has the UK in her sights!! As mentioned she is not expected to weaken much on her journey over the cooler waters of the N Atlantic....

Edited September 6, 2011 by james12

[Polar Bear]

She has the UK in her sights!! As mentioned she is not expected to weaken much on her journey over the cooler waters of the N Atlantic....

Hmm another october 87 maybe but sept 2011....?

Nar she will be long gone by then..

[Paul]

Nick F will be keeping tabs on Katia and her potential track toward the UK in a daily article over the coming days, read the first one here:

http://www.netweather.tv/index.cgi?action=news;storyid=790;sess=

[Liam J]

GFS 12z has her very close to the British Isles at 144hrs, Violent winds round the centre.

Of course the track will chop and change in the model runs over the coming days.

Edited September 6, 2011 by james12

[Alpine glow]

It looks interesting next Sunday! I have watched Katia since she was born, here and on Accuweather US.

She is a beauty to watch

http://www.stormpulse.com/atlantic

[Nick F]

NHC now have Katia as a cat 2 status hurricane with sustained winds of 105mph with higher gusts.

Classic GFS dartboard low moving NE toward Iceland early next week - the ex-tropical Katia.

[Coast]

Nick F will be keeping tabs on Katia and her potential track toward the UK in a daily article over the coming days

What effect do we think the jet stream will have on her? It looks like it's pushing everything right over the UK at the moment, could she hit the NW of England rather than Iceland as shown in my crude diagram yesterday?

Still packing 80mph on her way over:

But will she head North of us?

[Iceberg]

Katia is certaintly suffering from considerable shear atm.

[Coast]

Hmmm, I know this is a wide path, but.......

Would the wind-speeds still be circa 80mph as it closes in then?

[Liam J]

Hmmm, I know this is a wide path, but.......

Would the wind-speeds still be circa 80mph as it closes in then?

The winds would certainly still be hurricane strength with sustained 80mph, but I don't think it can be classed as a hurricane once it's this far west and north?

[Coast]

The winds would certainly still be hurricane strength with sustained 80mph, but I don't think it can be classed as a hurricane once it's this far west and north?

Will this not be an Extratropical storm/cyclone or an Ex-tropical storm??

I'd also be interested to know if the models will put in 'the Katia effect' i.e. is this including the potential?

[Liam J]

Will this not be an Extratropical storm/cyclone or an Ex-tropical storm??

I'd also be interested to know if the models will put in 'the Katia effect'?

Extratropical storm is the correct term I think, calling her 'EX' does not do her justice while she is packing winds of 80mph (cat 1 hurricane) across the Atlantic!!

[chionomaniac]

What effect do we think the jet stream will have on her? It looks like it's pushing everything right over the UK at the moment, could she hit the NW of England rather than Iceland as shown in my crude diagram yesterday?

This is the question that I have been wondering and to determine how Katia will be affected and the path she takes I have been looking at the upper ST jet stream forecasts for the period coming up.

The first thing to note is as Katia crosses the sub tropical jet and becomes extra tropical she will be weakened somewhat by the upper winds trying to decapitate her. However, when she reaches the northern aspect of the STJ then this is where the fun can begin.

At present Katia is forecast to cross the STJ at around T+96. The 200hPa jet stream charts show Katia's interaction with the STJ as a reverse V shape notch on the southern side of the Jet stream out in the Atlantic. Katia is strong enough to affect the jetstream.

The following 24 hours from this point will be critical in determining Katia's strength and position and in my opinion the most difficult to forecast.

If, as the GFS suggests, Katia crosses the STJ and coincides with a jet steak ( as highlighted ) this will have the affect of re-intensifying the storm system and NW Scotland could be in for an interesting time.

c

[Coast]

If, as the GFS suggests, Katia crosses the STJ and coincides with a jet steak ( as highlighted ) this will have the affect of re-intensifying the storm system and NW Scotland could be in for an interesting time.

Thank you Chiono, going to be one to follow!

[Robbie Garrett]

Shame there isn't a strong high pressure at Greenland at the moment, as then UK could get a direct hit from Katia. Otherwise it's going to go right over the top of Iceland, and then disintegrate.

[Methuselah]

Shame there isn't a strong high pressure at Greenland at the moment, as then UK could get a direct hit from Katia. Otherwise it's going to go right over the top of Iceland, and then disintegrate.

And that's worth a sigh of relief!

[Radiating Dendrite]

And that's worth a sigh of relief!

Agree.

I am quite attached to my Roof!

[knocker]

The 120 hour forecast puts it pretty near bang over the old weather ship station India. Oh they were heady days.

WTNT42 KNHC 070849

TCDAT2

HURRICANE KATIA DISCUSSION NUMBER 37

NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011

500 AM AST WED SEP 07 2011

THE CLOUD PATTERN OF KATIA HAS BECOME A LITTLE LESS ORGANIZED

OVERNIGHT. CLOUD TOP TEMPERATURES HAVE GENERALLY BEEN WARMING AND

DRY AIR APPEARS TO WRAPPING AROUND THE WESTERN SEMICIRCLE OF THE

CIRCULATION...THE LATTER GIVING THE CYCLONE A SOMEWHAT HOLLOW

APPEARANCE. IN ADDITION...THERE APPEARS TO BE NORTHWESTERLY SHEAR

OVER THE HURRICANE...AS EVIDENCED BY CIRRUS CLOUD MOTIONS AND

CONFIRMED BY UW-CIMSS ANALYSES. DVORAK T- AND CI-NUMBERS FROM TAFB

AND SAB ARE LOWER...AND A REASONABLE BLEND OF THESE DATA GIVES AN

INTENSITY ESTIMATE OF 80 KT. AN EYEWALL REPLACEMENT CYCLE THAT

BEGAN 24-36 HOURS APPEARS TO HAVE BEEN INTERRUPTED...WITH EARLIER

MICROWAVE IMAGERY SHOWING AN OUTER EYEWALL AT LARGE RADIUS THAT WAS

NOT CONTRACTING MUCH. THIS STRUCTURE...ALONG WITH THE MODERATE

SHEAR...SUGGESTS NOT MUCH CHANGE IN STRENGTH...FOLLOWED BY ONLY A

SLOW WEAKENING DURING THE NEXT FEW DAYS AS KATIA REMAINS OVER

RELATIVELY WARM WATERS. AFTER 72 HOURS...KATIA WILL QUICKLY MOVE

ALONG A STRONG GRADIENT OF SSTS AND ENCOUNTER AN INCREASINGLY

BAROCLINIC ENVIRONMENT...BOTH OF WHICH SHOULD RESULT IN A RAPID

TRANSITION TO AN INTENSE EXTRATROPICAL CYCLONE. POST-TROPICAL

CYCLONE KATIA IS EXPECTED TO BE A SIGNIFICANT WEATHER SYSTEM OVER

THE FAR NORTH ATLANTIC FOR AT LEAST A COUPLE OF DAYS. THE OFFICIAL

NHC WIND SPEED FORECAST IS LOWERED IN ACCORDANCE WITH THE LATEST

INTENSITY GUIDANCE AND IS IN BEST AGREEMENT WITH THE MODEL

CONSENSUS.

THE INITIAL MOTION IS A FAIRLY SLOW 315/08. GLOBAL MODELS SHOW KATIA

GRADUALLY TURNING FROM NORTHWESTWARD TO NORTHWARD INTO A WEAKNESS

IN THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC DURING THE NEXT

24-36 HOURS. AFTER THAT...THE HURRICANE IS EXPECTED TO GRADUALLY

RECURVE INTO THE WESTERLIES AND ACCELERATE NORTHEASTWARD ON THE

SOUTH SIDE OF A BROAD TROUGH COVERING THE FAR NORTH ATLANTIC. THE

TRACK GUIDANCE HAS CONSISTENTLY BEEN HANDLING THE STEERING FLOW

AROUND THE STORM WELL FOR SEVERAL FORECAST CYCLES AND IS TIGHTLY

CLUSTERED...GIVING HIGH CONFIDENCE TO THE FORECAST. ONLY MINOR

CHANGES WERE MADE TO THE PREVIOUS FORECAST TRACK...WITH THE CURRENT

NHC TRACK AGAIN CLOSE TO THE MULTI-MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 07/0900Z 28.7N 67.9W 80 KT 90 MPH

12H 07/1800Z 29.8N 69.0W 80 KT 90 MPH

24H 08/0600Z 31.7N 69.6W 75 KT 85 MPH

36H 08/1800Z 34.0N 69.5W 75 KT 85 MPH

48H 09/0600Z 36.4N 67.9W 70 KT 80 MPH

72H 10/0600Z 40.9N 58.2W 65 KT 75 MPH

96H 11/0600Z 47.0N 38.0W 65 KT 75 MPH...POST-TROP/EXTRATROP

120H 12/0600Z 59.0N 17.5W 65 KT 75 MPH...POST-TROP/EXTRATROP

$$

FORECASTER KIMBERLAIN/PASCH

[Coast]

Thank you Chiono, going to be one to follow!

Dedicated thread now open here for the effects (if any) of Katia on the UK:

http://forum.netweat...-to-hit-the-uk/

[lorenzo]

If, as the GFS suggests, Katia crosses the STJ and coincides with a jet steak ( as highlighted ) this will have the affect of re-intensifying the storm system and NW Scotland could be in for an interesting time.

c

Good post Chiono - I had a look at the JS pattern last night when catching up with the 8 or so pages here.

Proir to this time stamp it could have been drawn on with a ruler with its flat horizontal profile, both gun barrels pointed at the UK.

Have never watched this aspect of the models before, what will create the upgrade?Is it purely the kick from the jet streak?

Pretty amazing already that the storm system will remain potent all the way to our shores less the 6 degrees of sea temps it needs to feed from. Fascinating model watching.

My gut is telling me that similar to many storm systems of this nature that this will tilt North of Uk and flash the Shetland Isles, but Katia it seems has a determined look about her.

Edited September 7, 2011 by lorenzo

[chionomaniac]

Good post Chiono - I had a look at the JS pattern last night when catching up with the 8 or so pages here. Proir to this time stamp it could have been drawn on with a ruler with its flat horizontal profile, both gun barrels pointed at the UK. Have never watched this aspect of the models before, what will create the upgrade?Is it purely the kick from the jet streak? Pretty amazing already that the storm system will remain potent all the way to our shores less the 6 degrees of sea temps it needs to feed from. Fascinating model watching. My gut is telling me that similar to many storm systems of this nature that this will tilt North of Uk and flash the Shetland Isles, but Katia it seems has a determined look about her.

The critical thing that keeps Katia alive when she moves further north is the positioning of the jet stream. If Katia is positioned at the left exit of a jet streak then she will maintain or even increase wind speed. The left exit is the area where upper air of the jet stream is diverging. This in turn creates the imbalance that air from lower in the atmosphere will rush in to replace it. The lower air is left imbalanced then creating a convergence zone that will reinforce the baroclinic depression that Katia will have become.