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Hurricane Katia


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Interestingly enough all 6 of them have a slight bend back to WNW too at the end of the model run. Of course it's one run so take it for what its worth which is not a whole lot.

FWIW The 12z runs of them had an even more pronounced bend especially the CMCI

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I was talking about location only....Larry broke it down further to current heading, which obviously would suggest a further increase in recurve, but looking into the very short term, there is a good chance that we have will have a heading close to 270, and a recalculation based on historical data would most likely lead to a pretty good increase in LF chances with the new samples (maybe back to 20% or so....just guessing)

Just to clarify, my analysis is based strictly on the average heading from 25W to 30W for each storm. The current heading, once outside of 25-30W, is not being considered by this particular analysis. So, for this "tool", 293 deg. will always be used for Katia. Due to the apparently rather sig. negative correlation of the # of heading deg.'s in 25-30W and the chance for a CONUS hit, the idea is that knowing this heading would seemingly add some value over just using overall climo stats and it can be used in conjunction with global models in trying to assess the probability of a TC later making it to the CONUS while it is still in the E ATL. At the very least, I would think it could be used to try to assess whether it appears that the chance is larger than, close to, or smaller than overall climo, which is 23% in this case, while it is still in the E ATL. For Katia, it is suggesting much lower than the 23% overall climo chance. That, along with the models is why I'm going with only 10%. As a particular TC makes it closer to the W ATL and the models get a better grasp on things and other data/kinds of analogs become useful, the 25-30W heading becomes less and less useful although it can still be kept in mind.

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Katia gained hurricane status right about where historic climatology had suggested would likely be the case (between 39.5W-44.5W longitude). A combination of that development, the current guidance, and relatively low shear environment/warm SSTs suggests that Katia should grow into a major hurricane. A look at some of the major hurricanes that formed in the region in which Katia developed suggests that Katia should attain major hurricane status within 18-36 hours (sometime between 9/1 5 pm and 9/2 11 am), between 48.0W-53.0W longitude. There is a chance that Katia could attain major hurricane status during a rapid intensification cycle. Katia will likely peak as a Category 4 or perhaps Category 5 storm.

Right now, odds still favor Katia's recurving away from the U.S. Mainland. Both the 12z ECMWF ensembles and GFS 18z ensembles illustrate that recurvature. Both sets of ensembles bring Irene closer to the U.S. than some of the other guidance. In an extreme solution, the experiment FIM takes Katia on a track similar to Hurricane #4 in 1893, with the turn being wider. Hence, the storm makes landfall on the Delmarva Peninsula according to that model. More than likely, I suspect a track closer to Luis (1995) and possibly between Luis and Earl (2010). Nonetheless, the outcome is not yet certain and U.S. landfall cannot be ruled out.

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http://philstropical...gulf-of-mexico/

Here is my updated forecast on Hurricane Katia... I was too aggressive with intensification in the past 24 hours, but I still think a burst of rapid intensification is possible as alluded to in my forecast. However, beyond 24 hours I am against the NHC's forecast as the ECWMF forecasts the upper level flow to become southwesterly in front and over the storm and this should halt the intensification process and perhaps cause some modest weakening. Thus I'm forecasting a faster peak intensity for Katia and then some weakening in the 48-96 hour period as this southwesterly flow interrupts the intensification process. Beyond I still see the upper level trough lifting out and as the storm slows the anticyclone should build back in allowing intensification by the end of the forecast period.

mvn5o5.jpg

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cant really throw anything out since its so early...also your pic doesnt show up axesmiley.png

Its likely better it doesn't ;)

Not sure what to make of Katia tonight... there might be another dry air intrusion starting, but its difficult to confirm without microwave. It seems like the inner core was becoming established earlier and there is still a nice ball of convection near the center, so perhaps it may also be developing a tiny inner core. My forecast above is banking on the latter and not the former tongue.gif

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I can't really tell with the crap graphics, but looks as though UK is quite south and west:

I guess I should have noted that the on the model position error plot the EGRR, EGRI and EGR2 are the UKMET model, UKMET model Interpolated 06 hours and UKMET model Interpolated 12 hours respectively. The UKMET's are the best performing so far as of 0z ahead of the Canadians-CMC's

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Shear looks to be the real culprit per latest images.

I agree. Using the CIMSS wind analysis tool, it appears that overnight an area of 20 knot shear unexpectedly expanded and impacted the storm. Shear can be somewhat unpredictable at times and that is just one element that makes intensity forecasting so challenging. Certainly, both historic climatology (with aggressive strengthening of past storms in the region through which Katia is passing) and NHC suggested low shear for the time being.

In its 11 pm discussion, the NHC stated:

THE HURRICANE IS EXPECTED TO REMAIN IN A LOW SHEAR ENVIRONMENT AND OVER WARM WATER DURING THE NEXT DAY OR SO...WHICH SHOULD FAVOR ADDITIONAL STRENGTHENING.

In its 5 am discussion, the NHC noted:

AN AMSR-E OVERPASS AT 0451 UTC RATHER UNEXPECTEDLY SHOWED A PARTLY EXPOSED LOW-LEVEL CENTER WITH ONLY A FRAGMENT OF AN EYEWALL TO THE NORTH AND NORTHEAST.

There has been some relaxation of the shear in recent hours. At this point in time, it appears that Katia might be just under hurricane strength. It will be interesting to see whether it recovers by the 11 am advisory. If it's borderline, NHC might hold it at 75 mph and I don't think a continuity call under such circumstances would be a bad idea.

On a different front, the overnight modeling has moved into closer agreement with recurvature (with Katia probably coming as far west as 65W-70W). Of course, the experimental FIM ignored the growing model consensus. But with the ECMWF and GFS ensembles moving into better alignment with recurvature in the area outlined, the solution on the experimental FIM is likely a very low probability outcome.

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Hmm, maybe a little premature on the dry air comment. Shear looks to be the real culprit per latest images.

It's worth mentioning that the microwave image was taken when the shear vector was southerly at 10 knots which would enhance northerly inflow. I think without the dry air intrusion you wouldn't see this relatively light shear have such a great impact on the storm.

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GFS out to 192 is a major shift west. The 500MB set up on it also would suggest future runs it may come even more west. just 1 run but a major change for the model. lets see what the rest of the global models say before going crazy over this.

It would be hard-pressed to come that far west because of the ridge over the Midwest. Nonetheless, That is a very shallow trough on the GFS and the sudden and sharp recurve is evidence of a very zonal pattern. Things might be different if it can stay south of 25N.

12zgfs500mbHGHTPMSLtropical180.gif

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GFS out to 192 is a major shift west. The 500MB set up on it also would suggest future runs it may come even more west. just 1 run but a major change for the model. lets see what the rest of the global models say before going crazy over this.

maybe a bit west...but the general theme of ridge out west, trough in the east....still the same...and until that changes...no east coast landfall

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maybe a bit west...but the general theme of ridge out west, trough in the east....still the same...and until that changes...no east coast landfall

The question's been does it brush Bermuda or split the uprights between Bermuda and Hatteras. Unless this system shears out quite a bit over the next 48 hours and weakens to low end TS it's pretty much a go for a recurve at some point.

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One thing I just noticed is the only really comparable analog to the upcoming situation I know of (in recent times) involves Hurricanes Ivan & Jeanne. Ivan re-emerged over the Gulf for its second landfall as a very weak storm, and took a direction similar to what this storm may take, while Jeanne and Katia are going to be in similar (relative) locations as well.

Does anyone have the heights anomaly comparison between now and mid-September 2004?

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