ATL: KATE - Post-Tropical - Discussion

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#201 Postby cycloneye » Tue Nov 10, 2015 9:43 pm

TROPICAL STORM KATE DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122015
1100 PM AST TUE NOV 10 2015

The overall structure of Kate has not changed much since this
afternoon, however, the area of cloud tops has expanded and cooled
within the past few hours. NOAA reconnaissance aircraft data from
around 0000 UTC showed that the center remains embedded within the
central dense overcast, but there was significant tilt between the
700 mb and surface centers. Although flight-level winds and 0000
UTC Dvorak classifications support an intensity of 65 kt,
dropwindsonde and SFMR data indicate that the winds aloft are not
efficiently mixing down to the surface and the initial intensity
remains 60 kt.

There is only a short window of opportunity for Kate to reach
hurricane strength, before it moves over cooler waters and the
shear increases to more than 30 kt by Wednesday morning. Kate is
expected to remain a powerful cyclone as it becomes extratropical
in about 36 hours. Later in the period, Kate is forecast to
gradually weaken as it loses baroclinic forcing. The extratropical
low is forecast to be absorbed by a front over the north Atlantic in
4 to 5 days.

The initial motion estimate is 055/30 kt. Kate should continue
moving rapidly northeastward or east-northeastward during the next
24 hours, then temporarily slow down during the 36 to 48 hour time
period while it interacts with an upper-level trough. After that
time, the extratropical low should again accelerate northeastward
over the north-central Atlantic. The model guidance is in very good
agreement on this scenario, and the updated track forecast is
essentially an update of the previous advisory.

The extratropical portion of Kate's forecast was coordinated with
the NOAA Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 11/0300Z 33.9N 69.5W 60 KT 70 MPH
12H 11/1200Z 36.0N 64.0W 65 KT 75 MPH
24H 12/0000Z 38.9N 55.7W 65 KT 75 MPH
36H 12/1200Z 41.6N 50.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 13/0000Z 42.6N 49.4W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 14/0000Z 44.0N 41.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 15/0000Z 50.0N 28.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 16/0000Z...ABSORBED

$$
Forecaster Brown
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#202 Postby Hammy » Tue Nov 10, 2015 10:04 pm

Next advisory would likely be the last chance this has to strengthen any before it's overtaken by shear. The mid-level eye that was present earlier is no longer there so the structure is likely already on the decline.
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#203 Postby CrazyC83 » Tue Nov 10, 2015 10:22 pm

Baroclinic forcing could act to strengthen it as it becomes extratropical though.
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#204 Postby EquusStorm » Tue Nov 10, 2015 10:43 pm

So many storms in that part of the Atlantic this late in the year seem to require a lot of baroclinic influence to make that final push over the hurricane threshold. I just wonder if it will still be tropical enough to have official advisories at that point.
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...but still, though, a lot more interesting than the 2013 season.

Not a meteorologist, in fact more of an idiot than anything. You should probably check with the NHC or a local NWS office for official information.

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ATL: KATE - Tropical Storm - Discussion

#205 Postby WeatherEmperor » Wed Nov 11, 2015 12:53 am

I still find it amazing to get a named storm in November on probably the most powerful el nino on record. Simply amazing and it could reach hurricane intensity just wow.


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Re: ATL: KATE - Tropical Storm - Discussion

#206 Postby Hammy » Wed Nov 11, 2015 4:02 am

Kate is now the first hurricane to occur in November interestingly since the last El Nino in 2009.

And this makes three for three for the name.
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Re: ATL: KATE - Hurricane - Discussion

#207 Postby cycloneye » Wed Nov 11, 2015 9:42 am

HURRICANE KATE DISCUSSION NUMBER 11
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122015
1100 AM AST WED NOV 11 2015

An SSMIS microwave image from a few hours ago indicated that Kate is
well organized, with a large eye feature and a curved band that
almost completely surrounds it. During the past few hours, however,
the cloud tops have been warming, likely due to its passage over
decreasing SSTs. The initial wind speed remains 65 kt, based on
the latest Dvorak CI-numbers from TAFB and SAB.

The vertical wind shear is increasing over Kate, and it is expected
to be in excess of 40 kt later today. In addition, a strong
mid-latitude trough is approaching the cyclone. Based on these
expected conditions, it appears likely that Kate will transition to
an extratropical cyclone tonight or early Thursday. After the
transition, only a slow decay is predicted due to fairly strong
baroclinic forcing.

Kate is racing east-northeastward, and the latest initial motion
estimate is a speedy 065/39 kt. The hurricane is expected to slow
down later today and move erratically northeastward to east-
northeastward during the next couple of days when it interacts
with, and ultimately absorbs, an extratropical low to its west. A
faster northeastward motion is predicted by the weekend after the
merger of the weather systems. The new track forecast lies in the
middle of the tightly clustered guidance envelope.

The 34-kt and 50-kt wind radii have been expanded based on recent
scatterometer data. The extratropical portion of Kate's forecast
was coordinated with the NOAA Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 11/1500Z 36.8N 60.5W 65 KT 75 MPH
12H 12/0000Z 39.0N 55.1W 65 KT 75 MPH
24H 12/1200Z 41.1N 50.9W 65 KT 75 MPH...POST-TROP/EXTRATROP
36H 13/0000Z 41.8N 47.6W 60 KT 70 MPH...POST-TROP/EXTRATROP
48H 13/1200Z 42.4N 43.5W 55 KT 65 MPH...POST-TROP/EXTRATROP
72H 14/1200Z 48.5N 29.9W 50 KT 60 MPH...POST-TROP/EXTRATROP
96H 15/1200Z 56.1N 16.7W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 16/1200Z...DISSIPATED

$$
Forecaster Cangialosi
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Re: ATL: KATE - Hurricane - Discussion

#208 Postby Sanibel » Wed Nov 11, 2015 12:18 pm

Could be the Nino delayed the onset of the harsher jet that would have descended by now in a normal season.
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#209 Postby cycloneye » Wed Nov 11, 2015 3:36 pm

HURRICANE KATE DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122015
500 PM AST WED NOV 11 2015

Kate is not expected to be a tropical cyclone much longer. The
cloud pattern has become asymmetric, due to very strong westerly
shear, with the low-level center displaced to the west of the
associated deep convection. In addition, stable stratocumulus
clouds are wrapping around the south side of the circulation, and
there is some evidence of a developing warm front to the east of the
center. The initial intensity is held at 65 kt, based on the
Dvorak CI-numbers from TAFB and SAB. The combination of continued
strong shear and the interaction with an extratropical cyclone,
located just to the west of Kate, should cause the hurricane to lose
tropical characteristics tonight. After extratropical transition,
only a slow decay is predicted due to fairly strong baroclinic
forcing. The new intensity forecast is largely an update of the
previous one.

Kate continues to race east-northeastward, and the latest initial
motion estimate is about the same as before, 065/38 kt. A slowdown
is expected to begin soon, and an erratic northeastward to
east-northeastward motion is likely during the next couple of days
while Kate interacts with, and then absorbs, the extratropical low
to its west. After Kate and the extratropical low merge Thursday
night or early Friday, a faster northeastward motion is expected.
The new track forecast remains near the middle of the guidance
envelope.

This forecast was coordinated with the NOAA Ocean Prediction Center.

FORECAST POSITIONS AND MAX WINDS

INIT 11/2100Z 38.2N 56.4W 65 KT 75 MPH
12H 12/0600Z 40.1N 52.3W 65 KT 75 MPH...POST-TROP/EXTRATROP
24H 12/1800Z 41.5N 48.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
36H 13/0600Z 42.2N 45.1W 55 KT 65 MPH...POST-TROP/EXTRATROP
48H 13/1800Z 43.9N 40.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 14/1800Z 51.9N 25.3W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 15/1800Z 57.7N 13.4W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 16/1800Z...DISSIPATED

$$
Forecaster Cangialosi
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Re: ATL: KATE - Tropical Storm - Discussion

#210 Postby Ken Lucas » Wed Nov 11, 2015 6:02 pm

Hammy wrote:Recon is only showing 50kt surface winds on the first pass and there is only a small area of east winds on the northern side, so with this and shear increasing I'll wager this is going to be on the decrease during this mission. Radar presentation is also poor. I stand by my expectations that it won't become a hurricane, especially with this being the last mission.


Are you surprised it became a hurricane?
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Re: ATL: KATE - Tropical Storm - Discussion

#211 Postby Hammy » Wed Nov 11, 2015 6:08 pm

Ken Lucas wrote:
Hammy wrote:Recon is only showing 50kt surface winds on the first pass and there is only a small area of east winds on the northern side, so with this and shear increasing I'll wager this is going to be on the decrease during this mission. Radar presentation is also poor. I stand by my expectations that it won't become a hurricane, especially with this being the last mission.


Are you surprised it became a hurricane?


I honestly am. Given the wind profile I was seeing at the time it appeared it may be absorbed within a short time of that, especially given the speed, but the wind field seemed to reconsolidate over night and expand northwestward.
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Re: ATL: KATE - Hurricane - Discussion

#212 Postby cycloneye » Wed Nov 11, 2015 9:42 pm

TROPICAL STORM KATE DISCUSSION NUMBER 13
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122015
1100 PM AST WED NOV 11 2015

Kate continues to undergo extratropical transition. Satellite
imagery show that Kate's cloud pattern has become increasingly
elongated and asymmetric since the last advisory due to strong
westerly shear. The cloud pattern has also taken on a comma-shape
appearance, typically a precursor to frontogenesis and a completion
of extratropical transition. The initial intensity is lowered to 60
kt, based on a blend of Dvorak CI-numbers from TAFB and SAB. A mid-
to upper-level trough is forecast to merge with Kate in about 12
hours or so, which should result in Kate's becoming post-tropical.
After this occurs, baroclinic forcing from the trough should allow
the post-tropical cyclone to maintain its intensity or perhaps even
re-strengthen as indicated in the global models through about 24
hours. Beyond this time, a slow decay is forecast, with the post-
tropical cyclone predicted to lose its identity in about 3 days
when a new baroclinic development over the far north Atlantic
becomes more dominant. The new intensity forecast represents an
update of the previous one, with dissipation now shown a day sooner.

Kate continues to move rapidly east-northeastward but appears to
have slowed down some, and the initial motion estimate is 065/36.
As a post-tropical cyclone, Kate's motion is forecast to decrease
further during the next during 24 hours while it merges with the
extratropical system to the west. A new and potent shortwave
trough reaching Atlantic Canada in 2 to 3 days should then cause
Kate to accelerate east-northeastward to northeastward until
dissipation. The new track forecast is generally slower relative
to the previous one, consistent with the multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 40.1N 52.3W 60 KT 70 MPH
12H 12/1200Z 41.2N 50.0W 60 KT 70 MPH...POST-TROP/EXTRATROP
24H 13/0000Z 42.2N 46.8W 55 KT 65 MPH...POST-TROP/EXTRATROP
36H 13/1200Z 43.1N 43.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 14/0000Z 45.3N 37.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 15/0000Z 53.8N 22.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 16/0000Z...DISSIPATED

$$
Forecaster Kimberlain
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#213 Postby Dean_175 » Wed Nov 11, 2015 9:43 pm

I am guessing that this is going to end up being declared post-tropical before 8am EST tomorrow (at the latest). Satellite shows that it is starting to transition, and both the 18Z GFS and the 00Z NAM show signs of frontal structure developing later tonight/early morning tomorrow- with 850-1000mb thickness gradient through the center and a broadening of the isobars.
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Re: ATL: KATE - Tropical Storm - Discussion

#214 Postby tatertawt24 » Wed Nov 11, 2015 10:50 pm

Wow, she moved really fast!
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#215 Postby cycloneye » Thu Nov 12, 2015 4:51 am

Bye Kate.

POST-TROPICAL CYCLONE KATE DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122015
500 AM AST THU NOV 12 2015

Satellite imagery indicates that Kate has merged with a baroclinic
zone over the north Atlantic and is now an extratropical cyclone.
The advisory intensity is set at 60 kt based on earlier ASCAT-A data
and continuity from the previous advisory. The post-tropical
cyclone should gradually weaken during the next 2-3 days as it
merges with a low pressure area currently located to its west.
After that time, the global models show an intensifying baroclinic
low over the northeastern Atlantic, but it is unclear whether this
low is the re-intensification of the former Kate or a new low that
absorbs the remnants of Kate. The official forecast follows the
previous forecast in using the latter scenario.

The initial motion is 060/23. The post-tropical cyclone should
slow its forward motion during the next 24 hours or so during the
merger with the low to the west, and some erratic motion is
possible. Subsequently, the post-tropical cyclone should accelerate
toward the east-northeast and northeast. The new forecast track is
again slower than the previous forecast and is in best agreement
with the consensus models.

This is the last advisory on this system issued by the National
Hurricane Center. Additional information on this system can be
found in High Seas Forecasts issued by the National Weather Service,
under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and available
on the Web at http://www.opc.ncep.noaa.gov/shtml/NFDHSFAT1.shtml.


FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 40.7N 50.8W 60 KT 70 MPH...POST-TROP/EXTRATROP
12H 12/1800Z 41.8N 48.3W 55 KT 65 MPH...POST-TROP/EXTRATROP
24H 13/0600Z 42.2N 45.6W 45 KT 50 MPH...POST-TROP/EXTRATROP
36H 13/1800Z 43.3N 41.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
48H 14/0600Z 46.3N 35.2W 45 KT 50 MPH...POST-TROP/EXTRATROP
72H 15/0600Z 55.0N 19.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 16/0600Z...ABSORBED BY EXTRATROPICAL LOW

$$
Forecaster Beven
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