Hurricane KATIA

maquiladora

...KATIA SPARRING WITH STRONG UPPER-LEVEL WINDS...KNOCKED DOWN TO A TROPICAL STORM FOR THE SECOND TIME...

5:00 PM AST Sat Sep 3
Location: 19.9°N 56.8°W
Max sustained: 70 mph
Moving: WNW at 10 mph
Min pressure: 993 mb

DVORAK INTENSITY ESTIMATES HAVE FALLEN THROUGH THE DAY AND ARE NOW
T3.0/4.0 FROM TAFB AND T3.5/3.5 FROM SAB. BASED ON THE STRUCTURE
NOTED IN EARLIER MICROWAVE DATA...IT APPEARS THAT KATIA HAS
WEAKENED SOME AND AGAIN IS A TROPICAL STORM. FLUCTUATIONS IN
INTENSITY BY 5 TO 10 KT ARE POSSIBLE OVER THE NEXT DAY OR SO...BUT
THIS FACT WILL ONLY BE MORE APPARENT THAN USUAL SINCE THE INTENSITY
WOULD BE OSCILLATING AROUND THE 65-KT HURRICANE THRESHOLD.

IT CANNOT BE STRESSED ENOUGH THAT THERE IS CONSIDERABLE UNCERTAINTY
IN THE TRACK FORECAST...WHICH IS EXTREMELY SENSITIVE TO THE
EVOLUTION OF TROPICAL STORM LEE AND ITS INTERACTION WITH A MID-
TO UPPER-LEVEL LOW OVER THE EASTERN UNITED STATES. THE MODEL
GUIDANCE IS IN PRETTY GOOD AGREEMENT DURING THE FIRST 36 HOURS OR
SO...BUT THE DIVERGENCE ONLY GROWS FROM THERE. COMPARED TO THE
PREVIOUS FORECAST CYCLE...THE UKMET HAS SHIFTED TO THE NORTH AND
THE GFS HAS SLOWED DOWN...WHICH NORMALLY WOULD HAVE INCREASED
CONFIDENCE IN THE FORECAST. FURTHERMORE...THE ECMWF...WHICH IS
NORMALLY RELIABLE...SWUNG FROM THE NORTH AND EAST SIDE OF THE
GUIDANCE TO THE SOUTH AND WEST SIDE...SHOWING A MORE WESTWARD
MOTION BY DAY 5. THE OFFICIAL TRACK FORECAST HAS BEEN NUDGED A BIT
TO THE WEST TOWARDS THE VARIOUS CONSENSUS MODELS...BUT WE WOULD
RATHER SEE SOME STABILITY IN THE MODELS BEFORE MAKING A LARGER
SHIFT.

NEEDLESS TO SAY...THE INTENSITY FORECAST IS ALSO COMPLEX. KATIA HAS
NOT BEEN STRENGTHENING AS ANTICIPATED...AND UPPER-LEVEL WINDS DO
NOT APPEAR AS THOUGH THEY WILL BE CONDUCIVE FOR SIGNIFICANT
INTENSIFICATION FOR THE NEXT 24 TO 48 HOURS. THE UPPER-LEVEL
ENVIRONMENT AROUND KATIA BECOMES MORE UNCERTAIN AFTER
THAT TIME DEPENDING ON THE POSITIONING OF THE EASTERN U.S.
MID-/UPPER-LEVEL LOW. THE STATISTICAL SHIPS AND LGEM MODELS DO NOT
STRENGTHEN KATIA BEYOND CATEGORY 1 STATUS WHEREAS THE GFDL AND HWRF
STILL SHOW THE STORM REACHING MAJOR HURRICANE STRENGTH. THE
OFFICIAL INTENSITY FORECAST IS STILL NEAR OR JUST ABOVE THE
INTENSITY CONSENSUS...ESPECIALLY AT DAYS 4 AND 5.

FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 19.9N 56.8W 60 KT 70 MPH
12H 04/0600Z 20.7N 58.1W 65 KT 75 MPH
24H 04/1800Z 21.8N 59.8W 65 KT 75 MPH
36H 05/0600Z 23.1N 61.5W 70 KT 80 MPH
48H 05/1800Z 24.3N 63.2W 75 KT 85 MPH
72H 06/1800Z 27.0N 66.0W 85 KT 100 MPH
96H 07/1800Z 29.5N 69.0W 90 KT 105 MPH
120H 08/1800Z 31.5N 70.5W 85 KT 100 MPH

maquiladora

THERE HAS BEEN A SIGNIFICANT WESTWARD SHIFT IN
THE GUIDANCE THIS CYCLE...ALONG WITH A NOTABLE INCREASE IN THE
SPREAD. THE OFFICIAL TRACK AT THIS LONGER RANGE IS OF SOMEWHAT
LOWER CONFIDENCE...GIVEN THE SPREAD...AND IS ADJUSTED TO THE
LEFT...BUT NOT AS FAR LEFT AS THE LATEST MULTI-MODEL CONSENSUS.

0Z ECM :


0Z NOGAPS :


And Joe Bastardi tweeted this madness from the JMA. :rolleyes: Look at the pressure.

gbee

maquiladora wrote: »

0Z ECM : And Joe Bastardi tweeted this madness from the JMA. :rolleyes: Look at the pressure.

A typo surely?

Su Campu

Amazing disparity between the ECMWF and NOGAPS there. Going on the formula Max wind = 6.3xSquare Root(1013 - Po), the difference in max winds between both is 23 m/s, or around 45 knots - around 3 Saffir-Simpson categories! Nogaps is barely Cat 1, ECMWF is Cat 3/4! As for the JMA....... :rolleyes:

maquiladora

gbee wrote: »

A typo surely?

Well, the JMA is a model not known for being used to forecast tropical cyclones in the Atlantic. I think he justed tweeted it for laughs.

TheMilkyPirate

892, LOL!

maquiladora

Back to hurricane status again. Katia is a bit stronger than the NHC thought. They weren't forecasting her to reach 75mph for another 12 hours but based on a close pass to a buoy they have upgraded her to 75mph already.

AT 6 AM AST...1000 UTC...NOAA BUOY 41044 LOCATED TO THE NORTHEAST OF
THE NORTHERN LEEWARD ISLANDS REPORTED A 1-MINUTE SUSTAINED WIND OF
69 MPH...111 KM/H...AND A GUST TO 83 MPH...133 KM/H...JUST TO THE
NORTHWEST OF THE CENTER OF KATIA. BASED ON THIS INFORMATION...
KATIA IS UPGRADED AGAIN TO A HURRICANE.

Su Campu

That buoy is 16 nautical miles from the centre and is reporting 72 knots (80 mph) sustained winds at 1200.

http://www.ndbc.noaa.gov/station_page.php?station=41044

ninebeanrows

She is developing rapidly this afternoon.

She has developed a visible eye in the last few hours.

http://www.ssd.noaa.gov/goes/east/carb/flash-vis.html

200motels

Interesting developments these past few hours, I think this hurricane could reach cat5 late next week.

maquiladora

12Z models have shifted away from the US east coast. Recurve between Bermuda and the US looking more and more likely.

The models were run before Katia started rapidly intensifying (could well be Cat 3 on the next advisory), and a stronger storm usually moves even more poleward.

dsmythy

If Katia were to take Lee under her wing would this be cause for intensification or would it weaken her?

200motels

This from Accuweather.com
Tropical Storm Lee Spreading Heavy Rain Inland; Hurricane Katia Strengthening Rapidly
Hurricane Katia has quickly strengthened to a Category 2 hurricane with sustained winds of 100 mph as of late Sunday morning. Current satellite imagery shows that an eye is beginning to form, certainly a sign that Katia will continue to deepen this afternoon and tonight. The shear that was hindering the development of Katia seems to have weakened enough to allow thunderstorms to blossom and wrap themselves about the center of circulation. Katia should deepen to a major hurricane (a major hurricane is a storm that is Category 3 or higher) by late Monday or Monday night. Katia should continue on its northwesterly track this afternoon and tomorrow, although it may slow its forward speed over the next few days as well. Eventually, Katia should make a more northward turn later in the week between Cape Hatteras and Bermuda as an upper-level trough moving across the eastern United States should pick up Katia and steer it northward. Computer forecast models continue to trend westward with the path of Katia, so the storm seems likely to pass closer to Cape Hatteras than Bermuda. In fact, it is possible that by late in the week, the center of Katia may come as close as 200 to 250 miles from Cape Hatteras. But, this distance would still be great enough for Katia to pass safely east of the United States. However, all interests along the East Coast, especially the Outer Banks of North Carolina, should continue to pay careful attention to Katia over the next few days. Although Katia will have no direct impact on land over the next few days, the storm will continue to send swells and rough surf to north- and east-facing shores of the Lesser and Greater Antilles today and tomorrow. The rough surf and higher swells will then impact Bermuda starting tomorrow. Eventually, the rough surf and swells will reach the East Coast of the United States by the middle of the week.

ninebeanrows

Looks like Katia will turn into an extremely intense extra-tropical storm by Day 7, still unlikely to threaten Ireland according to latest model plots.

munsterlegend

i presume judging by that chart that it will head north of us? is the east coast of america still unlikely to be hit due to its recurve?

maquiladora

munsterlegend wrote: »

i presume judging by that chart that it will head north of us? is the east coast of america still unlikely to be hit due to its recurve?

Yes, it's highly likley that Katia will recurve without hitting the US east coast, there is good model consensus on this now.

At the moment it looks like ex-Katia would pass to our north.

ninebeanrows

Katia still expected to be an extreme storm to our WNW in 7 days.

Some nice surf for the west coast.

ninebeanrows

Katia is a real quality looking hurricane right now.

Definately back to Major status atm.

http://www.ssd.noaa.gov/goes/east/carb/flash-vis.html

Hurricane hunters have decreased frequency of recon missions as it is not expected to threaten land.

M.T. Cranium

The plot thickens with regard to Katia's possible encounter with Ireland about a week from today (which by the way is full moon, making any strong winds that much more serious due to storm surge issues).

The GFS model has been consistently showing a very fast forward speed that allows Katia to gain latitude rapidly and swerve away from Ireland towards Iceland on Sunday, thus having a very indirect effect on the weather in Ireland. But up to last night, the ECM was showing a somewhat closer approach on a slower timetable. Now this morning (my time) the 12z GEM has Katia a full day slower on the same track out to day six, and heading into an Atlantic flow that does not look very capable of rebounding, in other words, it would almost certainly bring Katia much closer to Ireland, albeit a day later around Monday night perhaps (12-13 Sept).

So all eyes on ECM and UK models for their take on Katia's track ... results should be in between 9 and 10 p.m.

The GFS has in the past had issues with over-deepening this type of storm and over the past few years I've found it handy to assume the GFS is a day too fast with 6-8 day storm development, so I'm really hesitant to buy into the GFS solution at this point.

M.T. Cranium

And here's our answer -- the 12z ECM brings Katia directly across Ireland on Monday 12th, albeit in rapidly weakening form. The day 6 position was a little ahead of the GEM (which ends with day 6) so one might extrapolate the GEM to show an even more potent track for Ireland (something just past Mayo and Donegal would be the windiest outcome, this ECM solution would actually be more windy for the southwest part of England and wetter for Ireland).

The UK model was an epic fail as its day 6 panel has only the slightest hint of extratropical Katia but closer to the ECM than GEM.

Wow ... we have a hurricane remnant in the mix on day seven. :eek:

Maybe someone could post the link to the ECM as I am heading out here. Just to avoid any false reports or panic, the map interpretation would not give damaging wind gusts or storm surge potential in Ireland (winds of 30-50 mph, more like 50-70 mph well south and into the U.K.) but could give a heavy rainfall potential of 20-30 mms. So we're not actually seeing anything epic on any model yet, the worst case scenario for wind and storm surge would be a deep remnant low a bit further north than this ECM map shows.

Kippure

Here it comes



Uploaded with ImageShack.us

Right over us



Uploaded with ImageShack.us

M.T. Cranium

Back in again, the 144h NOGAPS has a more southerly track to the end of its run (still leaving the storm in the west-central Atlantic at that point on Sunday 11th) so, the normal forecasting procedure weighting these five models would say ... track across Atlantic northwest of Ireland, potential for a strong wind and moderate storm surge event on Monday or possibly Tuesday. No model shows this yet but that's the weighted consensus of all models.

My hunch is that the eventual solution will be like that, both the GFS and ECM have about equal tendencies to be off in the directions they are currently "off" from that consensus, and the GEM is trending towards this outcome ... since this forecast problem involves a lot of Canadian data input to set up the pattern, I would weight the GEM at least equal to GFS which is not always the case (different patterns receive different weighting considerations). If you want to get the inside scoop on that, when we have better data in a day or two, the weight you might want to assign would be like this:

ECM 5
GEM,GFS 4
UK, NOGAPS 3
JMA, GME 2

At this distance out I tend to factor in my research model in terms of timing lines and positions too, but the ECM is almost a direct match of that research model for position (adjust to north and west 3 deg for exact match).

Now I just want to caution that this scenario could fall apart at any stage, with hurricanes, you can never be too sure until recurvature has taken place, but with remnants of Lee pushing into the eastern U.S., recurvature has always looked just about "locked in" for Katia. There's always that southward dive solution that the NOGAPS seems to be searching for.

maquiladora

...KATIA BECOMES A MAJOR HURRICANE...BIGGEST THREAT CONTINUES TO BE DANGEROUS RIP CURRENTS ALONG THE U.S. EAST COAST AND BERMUDA...

5:00 PM AST Mon Sep 5
Location: 25.2°N 63.9°W
Max sustained: 115 mph
Moving: NW at 12 mph
Min pressure: 959 mb

000
WTNT42 KNHC 052039
TCDAT2

HURRICANE KATIA DISCUSSION NUMBER 31
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011
500 PM AST MON SEP 05 2011

VISIBLE SATELLITE IMAGERY SHOWS THAT KATIA HAS BECOME MORE ORGANIZED
THROUGH THE DAY WITH A WELL-DEFINED EYE AND EXCELLENT UPPER-LEVEL
OUTFLOW...ESPECIALLY OVER THE SOUTHERN SEMICIRCLE. HOWEVER...THE
INFRARED PRESENTATION IS LAGGING A BIT AND SHOWS A THINNING OF THE
DEEP CONVECTION OVER THE NORTHEASTERN QUADRANT. DVORAK ESTIMATES
FROM TAFB AND SAB ARE T5.5...AND THE INITIAL INTENSITY IS THEREFORE
RAISED TO 100 KT. OBJECTIVE DVORAK NUMBERS HAVE BEEN RUNNING
HIGHER...BUT WITH THE CONVECTION LACKING SYMMETRY AND A COOLING EYE
IN THE LAST FEW IMAGES...I WOULD RATHER WAIT TO RAISE THE INTENSITY
ANY HIGHER.

THE 12-HOUR SMOOTHED MOTION IS ABOUT 310/10 KT...AND KATIA IS
EXPECTED TO CONTINUE ON ITS NEARLY STRAIGHT TRACK FOR THE NEXT 48
HOURS AS IT MOVES AROUND A CENTRAL ATLANTIC MID-LEVEL ANTICYCLONE.
FAIRLY SHARP RE-CURVATURE IS SHOWN BY MOST OF THE MODELS AROUND DAY
3...AND THEY ARE TIGHTLY CLUSTERED WITH A TRACK THAT TAKES THE
CENTER ALMOST MIDWAY BETWEEN BERMUDA AND THE U.S. EAST COAST. AS
WAS THE CASE EARLIER TODAY...THERE IS STILL GREATER-THAN-NORMAL
SPREAD IN THE GUIDANCE AT 96 AND 120 HOURS DUE TO A LACK OF
AGREEMENT ON WHEN KATIA WILL BE SCOOPED UP BY STRONG MID-LATITUDE
WESTERLIES TO THE NORTH. HOWEVER...THE ECMWF AND UKMET HAVE SPED
UP A BIT AND THE GFS HAS SLOWED DOWN...SO THE UNCERTAINTY HAS
DECREASED SOMEWHAT. THE MOST SIGNIFICANT CHANGE TO THE NEW
FORECAST IS A SLIGHT NORTHWESTWARD SHIFT OF THE 96-HOUR POINT TOWARD
THE MULTI-MODEL CONSENSUS.

THE OFFICIAL FORECAST IS LARGELY UNCHANGED AND STILL LIES NEAR THE
UPPER END OF THE GUIDANCE. ONLY MODEST ADDITIONAL STRENGTHENING IS
FORECAST WITH KATIA EXPECTED TO MOVE OVER INCREASINGLY LESS
FAVORABLE OCEANIC CONDITIONS OVER THE NEXT SEVERAL DAYS. IN
ADDITION...THE SHIPS GUIDANCE IS INDICATING THAT VERTICAL SHEAR
COULD BE A LITTLE HIGHER BETWEEN 24 AND 72 HOURS THAN WAS
PREVIOUSLY SHOWN...AND THIS COULD ALSO LIMIT STRENGTHENING.
WEAKENING IS EXPECTED DURING THE LATTER PART OF THE FORECAST
PERIOD. THE GFS IS SHOWING KATIA BECOMING EXTRATROPICAL BY DAY
5...BUT SINCE IT IS THE FASTEST OF THE MODELS IT IS PROBABLY
SHOWING THIS A LITTLE TOO SOON.

FORECAST POSITIONS AND MAX WINDS

INIT 05/2100Z 25.2N 63.9W 100 KT 115 MPH
12H 06/0600Z 26.1N 64.9W 105 KT 120 MPH
24H 06/1800Z 27.3N 66.3W 105 KT 120 MPH
36H 07/0600Z 28.5N 67.8W 100 KT 115 MPH
48H 07/1800Z 29.7N 69.1W 100 KT 115 MPH
72H 08/1800Z 33.5N 70.5W 90 KT 105 MPH
96H 09/1800Z 38.5N 66.5W 75 KT 85 MPH
120H 10/1800Z 42.0N 54.0W 65 KT 75 MPH

$$
FORECASTER BERG

mike2084

M.T. Cranium wrote: »

Back in again, the 144h NOGAPS has a more southerly track to the end of its run (still leaving the storm in the west-central Atlantic at that point on Sunday 11th) so, the normal forecasting procedure weighting these five models would say ... track across Atlantic northwest of Ireland, potential for a strong wind and moderate storm surge event on Monday or possibly Tuesday. No model shows this yet but that's the weighted consensus of all models.

My hunch is that the eventual solution will be like that, both the GFS and ECM have about equal tendencies to be off in the directions they are currently "off" from that consensus, and the GEM is trending towards this outcome ... since this forecast problem involves a lot of Canadian data input to set up the pattern, I would weight the GEM at least equal to GFS which is not always the case (different patterns receive different weighting considerations). If you want to get the inside scoop on that, when we have better data in a day or two, the weight you might want to assign would be like this:

ECM 5
GEM,GFS 4
UK, NOGAPS 3
JMA, GME 2

At this distance out I tend to factor in my research model in terms of timing lines and positions too, but the ECM is almost a direct match of that research model for position (adjust to north and west 3 deg for exact match).

Now I just want to caution that this scenario could fall apart at any stage, with hurricanes, you can never be too sure until recurvature has taken place, but with remnants of Lee pushing into the eastern U.S., recurvature has always looked just about "locked in" for Katia. There's always that southward dive solution that the NOGAPS seems to be searching for.

This is worrying me for Listowel Races! Keep us informed and thanks for the great info as always

maquiladora

12Z ECM track could indeed bring stormy conditions if it hadnt weakened so rapidly between 144 and 168.

GFS 12Z ensembles.

Redsunset

200motels

This from Accuweather.com
Katia Now a Category 4; Lee Drops Heavy Rain
Katia has strengthened into a powerful a Category 4 hurricane, with sustained winds now up to 135 mph. Katia has been well organized over the past day or so as the hurricane traveled over very warm water. This dangerous storm is expected to avoid land this week, moving between Bermuda and the East Coast. A ridge of high pressure to the north of Katia is helping the storm to keep a western component to its movement. However, this ridge of high pressure will break down as the week progresses, allowing Katia to take a more northerly turn by the middle and latter part of the week. Nonetheless, we cannot rule out a farther west path that may have Katia brush southeast New England to Nova Scotia and Newfoundland. There is a low chance of this path, but it is something to monitor. The most likely track will keep Katia away from land before eventually losing tropical characteristics. Despite Katia staying away from land, big swells and rough surf will pound the East Coast this week. This is especially from the Outer Banks to New England Wednesday to Friday. Dangerous rip currents will increase in frequency this week; those heading into the surf should be on guard for dangerous conditions. Bermuda will not escape the dangerous increase in tides and rip currents this week either.

maquiladora

...KATIA BECOMES A CATEGORY FOUR HURRICANE...DANGEROUS RIP CURRENTS ARE THE MAIN HAZARD ALONG U.S. EAST COAST AND BERMUDA...

11:00 PM AST Mon Sep 5
Location: 25.8°N 64.4°W
Max sustained: 135 mph
Moving: NW at 10 mph
Min pressure: 946 mb

maquiladora

0Z GFS, showing ex-Katia to our west with max 70-74 knot sustained winds. The kind of sustained winds you'd expect in a mid-range Cat 1 hurricane. After this the GFS weakens it and it tracks to our northwest.

Sponge Bob

personally I think the GFS overcooks storms 7 days out. If it hits Ireland it will be a soggy event more than a windy one.