Hurricane Katia Part 2, TS Watch for Bermuda

[k***]

Deep convection has now wrapped all of the way around the eye...still has a long way to go to get that nice symmetrical look typical of something upper-end

Has anyone ever seen this much agreement between Satcon, ADT, and CIMSS AMSU?

[phil882]

Here are the maximum surface pressure and intensity maps, assuming optimal conditions, which is very unlikely hmm?

Those maps are suppose to show the theoretical maximum potential intensity (MPI) for a tropical cyclone given atmospheric variables and Sea Surface Temperatures. Given how rarely all the variables are "just right" I think its pretty unlikely that Katia will reach its MPI, especially given the warm upper level temperatures are forecasted to be which will likely limit the convection at a somewhat lower brightness temperature (and thus lower altitude) than normal. Mid-level dry air is also nearby the system which makes it more susceptible to dry air intrusions, which could still disrupt the satellite presentation were the shear to increase.

I think the main problem here is that every time somebody shouts the word Annular, people automatically start thinking this will be another Isabel. What most people seem to forget is that Isabel is one of the very few documented cases of a Cat 5 annular storm, with most other annular storms peaking in the Cat 3-4 threshold. Pictured below is a chart documenting Annular storms from (1995-2006) with Isabel being the only annular storm to reach category 5 intensity. Given past history and the given atmospheric conditions expected, I think its quite unlikely Katia will peak beyond the Category 4 threshold.

However, I do think Katia could become an annular hurricane candidate as it moves into cooler Sea Surface Temperatures. Currently, the temperatures are likely still a touch too warm to support "pure" annular conditions, but that will likely change in the next 24 hours if SHIPS is right.

If you are still interested, here is another published paper by Knaff and DeMaria (2008) that piggy backs of the ideas first presented in Knaff and DeMaria (2003).

[OKpowdah]

Deep convection has now wrapped all of the way around the eye...still has a long way to go to get that nice symmetrical look typical of something upper-end

Has anyone ever seen this much agreement between Satcon, ADT, and CIMSS AMSU?

Notice the two mesovortices in the eye

[dan88]

12z GFS shows heavy rain from the outer part of the NW quad affecting SE Canada with a glancing blow, center staying a good ways offshore.

[weathercheck]

GFS coming out now. Closer to the MAINE coast?

[Amped]

Parts of Central PA and WV really get the PRE this run. Johnstown is right in the bullseye.

[k***]

Those maps are suppose to show the theoretical maximum potential intensity (MPI) for a tropical cyclone given atmospheric variables and Sea Surface Temperatures. Given how rarely all the variables are "just right" I think its pretty unlikely that Katia will reach its MPI, especially given the warm upper level temperatures are forecasted to be which will likely limit the convection at a somewhat lower brightness temperature (and thus lower altitude) than normal. Mid-level dry air is also nearby the system which makes it more susceptible to dry air intrusions, which could still disrupt the satellite presentation were the shear to increase.

I think the main problem here is that every time somebody shouts the word Annular, people automatically start thinking this will be another Isabel. What most people seem to forget is that Isabel is one of the very few documented cases of a Cat 5 annular storm, with most other annular storms peaking in the Cat 3-4 threshold. Pictured below is a chart documenting Annular storms from (1995-2006) with Isabel being the only annular storm to reach category 5 intensity. Given past history and the given atmospheric conditions expected, I think its quite unlikely Katia will peak beyond the Category 4 threshold.

If you are still interested, here is another published paper by Knaff and DeMaria (2008) that piggy backs of the ideas first presented in Knaff and DeMaria (2003).

Sick post.

Here's another question that's worth pondering: are we jumping the gun by even bringing up annular storms? Will this just sort of remain quasi-annular and never fully transition? I was sure it was on the fast track to axisymmetry when I woke up this morning but now I am a little more wary.

[k***]

Notice the two mesovortices in the eye

Not trying to argue against it, but my eye can't distinguish mesovortex from debris on IR.

edit: I did loop the visible on the NASA site and the mesos are fairly defined.

[gkrangers]

Easy major hurricane at this hour, as symmetry is starting to improve.

Category 4 later should the trend continue.

[phil882]

Sick post.

Here's another question that's worth pondering: are we jumping the gun by even bringing up annular storms? Will this just sort of remain quasi-annular and never fully transition? I was sure it was on the fast track to axisymmetry when I woke up this morning but now I am a little more wary.

Here are the rules that I think SHIPS uses when attempting to define an Annular Hurricane (AH). This is taken from the same paper referenced above. It seems at this point we are still working on deltaT in the actual eye, and sea surface temperatures over the storm, but I expect the eye to continue to clear out somewhat today and sea surface temperatures are expected to decrease along the track. Its certainly not there yet, but as long as the shear remains low, this still has potential to become annular.

[gkrangers]

What does a mesovortex look like? I'm curious. If I were in the TIV 2, hunkered down, and I saw a mesovortex in front of me, would it be similar to a tornado? landspout?

http://wwwghcc.msfc.nasa.gov/GOES/goeseastconus.html

Just create a 20 image loop and click on the eye. You'll see.

[k***]

Here are the rules that I think SHIPS uses when attempting to define an Annular Hurricane (AH). This is taken from the same paper referenced above. It seems at this point we are still working on deltaT in the actual eye, and sea surface temperatures over the storm, but I expect the eye to continue to clear out somewhat today and sea surface temperatures are expected to decrease along the track. Its certainly not there yet, but as long as the shear remains low, this still has potential to become annular.

I always wondered what the prescreening criteria were. Looks like I need to read this 2008 paper.

[#NoPoles]

i don't want to clutter this thread with talk of annular characteristics, and how/why a hurricane becomes annular...so feel free to move this to ask a pro met thread...but i see this is where Phil is hanging out, i was wondering why a hurricane has a greater chance of developing an annular structure over lower SST's?

[phlwx]

Parts of Central PA and WV really get the PRE this run. Johnstown is right in the bullseye.

Katia may be throwing some additional moisture into the mix that's getting squeezed over the Apps but it's not a "classic" PRE as Lee's moisture and 500 low is already in the mix and already contributing to that.

If there were just an old trough there and no remnant tropical system it would be more characteristic of a PRE.

[k***]

http://rammb.cira.colostate.edu/products/tc_realtime/loop.asp?product=1kmsrvis&storm_identifier=AL122011&starting_image=2011AL12_1KMSRVIS_201109042045.GIF

[OKpowdah]

What does a mesovortex look like? I'm curious. If I were in the TIV 2, hunkered down, and I saw a mesovortex in front of me, would it be similar to a tornado? landspout?

They're identifiable on satellite and radar ... usually lower (warm) clouds along the eyewall that show distinct curvature and rotation. They're on a much larger scale than you're thinking.

[weathercheck]

Latest few frames really show this storm improving.

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

[OKpowdah]

The trend toward symmetry has faltered a bit...

[k***]

The trend toward symmetry has faltered a bit...

the spiral band to the north and west of it also seems to becoming more robust.

regardless, this thing is going to look awesome in 6 hours.

[k***]

there definitely might be something to the old LEK graphic showing the difference between the coiled look (think irene, alex etc) and katia's look where all the incoming vectors are coming inward relatively uninterrupted

[phil882]

i don't want to clutter this thread with talk of annular characteristics, and how/why a hurricane becomes annular...so feel free to move this to ask a pro met thread...but i see this is where Phil is hanging out, i was wondering why a hurricane has a greater chance of developing an annular structure over lower SST's?

Honestly, I'm not sure why... although my hunch is that it has something to do with the instability that higher SSTs might have towards generating rain-bands away from the center that would prevent true annular characteristics. There were cases I believe that Knaff and DeMaria (2003) mentioned where storms had the IR presentation of an annular storm in places with higher SSTs (Mitch, Floyd, Georges ect.) but did not fit the constraints in regards to having a stable eyewall or outer rain-bands.

[Srain]

then I demand a reason because my post was on topic to the actual topic here so enlighten me Mod!

Your previous post was hidden by one of the Red Tag Mods. Perhaps he will choose to discuss this matter at a later time via pm.

[Amped]

Weenies, the 12z GGEM only about 75 miles east of NC. Gets the outer banks below 996mb

http://www.meteo.psu.edu/~gadomski/CMC_12z/cmcloop.html

It's probably wrong,

This would be a good setup with the ULL in the TN Valley, however all models and me still agree the NRN stream will knock down the ridging over New England and ruin it.

[salbers]

Seems the CMC is allowing Katia to approach closer since it is retrogressing the Lee remnant cutoff a bit further westward into Missouri. This looks like an omega blocking pattern forming over the western US. Perhaps the CMC is having a slower motion of Katia to the NW and this allows the Lee cutoff time to migrate farther west, so it doesn't push it off the east coast as much.

[dan88]

Should have a major this afternoon, the 18z SHIPS was initialized at 100kt

[donsutherland1]

FWIW, 18z satellite data suggest that Katia has become a major hurricane (Dvorak scores somewhere in the T5.5 to T6.0 range).

[HoarfrostHubb]

No Katia images thread?

[dan88]

And we have a major.

HURRICANE KATIA FORECAST/ADVISORY NUMBER 31

NWS NATIONAL HURRICANE CENTER MIAMI FL AL122011

2100 UTC MON SEP 05 2011

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

INTEREST IN BERMUDA SHOULD MONITOR THE PROGRESS OF KATIA.

HURRICANE CENTER LOCATED NEAR 25.2N 63.9W AT 05/2100Z

POSITION ACCURATE WITHIN 10 NM

PRESENT MOVEMENT TOWARD THE NORTHWEST OR 310 DEGREES AT 10 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 959 MB

EYE DIAMETER 25 NM

MAX SUSTAINED WINDS 100 KT WITH GUSTS TO 120 KT.

[donsutherland1]

This afternoon, Katia became the 2011 season’s second major hurricane. At 5 pm, it was positioned at 25.2°N 63.9°W with maximum sustained winds of 115 mph. It has generally been tracking to the west-northwest over the past 24 hours, but may be in the early stages of turning to the northwest. A turn to the northwest is likely tonight, though another bend more to the west could develop afterward.

Trajectory for the 12-hour period ending:

9/4 11 pm: 308° NW

9/5 5 am: 298° WNW

9/5 11 am: 293° WNW

9/5 5 pm: 301° WNW

6-hour Motion: 315° NW

24-hour Motion: 300° WNW

With Hurricane #4 (1927) and Gladys (1975) remaining the leading analogs, I believe the GFS idea of a slower turn to the east than the ECMWF is probably the more likely outcome. Hence, Katia will likely cross 40°N latitude several degrees to the west of 60°W longitude.

At this time, my initial track remains in reasonably good shape. Despite the models oscillating from east of the estimated track to its west and then back to its east, there is little reason to adjust it at this time.

Estimated Track:

17.5N 52.8W; Actual: 17.5N 52.4; Error: 26 miles—1. 5 hours in advance

20.0N 56.8W; Actual: 20.0N 57.0W; Error: 13 miles—33.0 hours in advance

25.0N 63.9W; Actual: 25.0N 63.7W; Error: 13 miles—77.5 hours in advance

30.0N 72.0W

35.0N 69.6W

40.0N 63.5W

Finally, in terms of Katia’s intensity, it remains plausible that the storm will peak at Category 4 strength. Katia should be traversing waters with SSTs of 29°C or above over the next 36-48 hours.

[calamity]