ATL: KATE - Remnants - Discussion

[Teban54]

So, they named a naked swirl. I'll give them a pass after the week they have had

In Kate's defense, it looked great when the update was posted, with vigorous convection just on top of the LLC. It collapsed almost immediately after getting the name, though.

[cycloneye]

BULLETIN
Tropical Depression Ida Advisory Number 19
NWS National Hurricane Center Miami FL AL092021
400 PM CDT Mon Aug 30 2021

...IDA BECOMES A TROPICAL DEPRESSION OVER MISSISSIPPI...
...HEAVY RAINFALL AND FLASH FLOODING THREAT CONTINUES TO SPREAD
INLAND...


SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...32.6N 90.3W
ABOUT 20 MI...35 KM NNW OF JACKSON MISSISSIPPI
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNE OR 20 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

All Tropical Storm and Storm Surge Warnings have been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

There are no coastal watches and warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 400 PM CDT (2100 UTC), the center of Tropical Depression Ida was
located near latitude 32.6 North, longitude 90.3 West. The
depression is moving toward the north-northeast near 9 mph (15
km/h). A faster northeastward motion is expected tonight through
Wednesday. On the forecast track, the center of Ida will move
farther inland over central and northeastern Mississippi tonight.
Ida is then forecast to move across the Tennessee Valley on
Tuesday and near the central Appalachians on Wednesday.

Maximum sustained winds have decreased to near 35 mph (55 km/h)
with higher gusts. Additional weakening is forecast during the
next day or so.

The minimum central pressure estimated from surface observations is
999 mb (29.50 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Ida can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT4, WMO header WTNT44 KNHC,
and on the web at hurricanes.gov/graphics_at4.shtml?key_messages.

STORM SURGE: Water levels along the northern Gulf coast should
continue to subside through this evening.

RAINFALL: Through Tuesday morning across portions of southeast
Louisiana into far southern Mississippi, Ida will produce additional
rainfall totals of 2 to 4 inches with localized higher amounts
possible. Storm total rainfall accumulations of 10 to 18 inches with
isolated maximum amounts of 24 inches is expected. Heavy rain
combined with storm surge has resulted in catastrophic impacts along
the southeast coast of Louisiana with considerable flash flooding
and riverine flooding continuing farther inland.

Ida will continue to turn northeast this evening and is forecast to
track across the Middle Tennessee Valley, Ohio Valley and
Mid-Atlantic through Wednesday, producing the following rainfall
totals:

Coastal Alabama to the far western Florida panhandle: An additional
3 to 6 inches resulting in storm total accumulations of 6 to 12
inches with isolated maximum amounts of 15 inches, today through
Tuesday morning.

Central Mississippi into far western Alabama: 4 to 8 inches with
isolated maximum amounts of 12 inches, today through tonight.

Middle Tennessee Valley, Ohio Valley, Central/Southern Appalachians
into the Mid-Atlantic: 3 to 6 inches with isolated higher amounts,
Tuesday into Wednesday.

Southern New England: 2 to 4 inches with isolated higher amounts,
Wednesday into Thursday.

Considerable flash flooding is possible from the Lower Mississippi
Valley through the Middle Tennessee Valley, Ohio Valley,
Central/Southern Appalachians, and into the Mid-Atlantic. Widespread
minor to isolated major riverine flooding is occurring or forecast
from the Lower Mississippi Valley into far western Alabama. Rivers
will remain elevated into next week.

TORNADOES: A few tornadoes are possible through tonight, mainly
across far southeast Mississippi, the southern half of Alabama, and
the western Florida Panhandle. The threat for a few tornadoes will
shift east on Tuesday and become centered across eastern Alabama,
western Georgia, and the Florida Panhandle.

SURF: Swells will continue to affect portions of the northern Gulf
coast through this evening. These swells are likely to cause life-
threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
This is the last public advisory issued by the National Hurricane
Center on Ida. Future information on Ida can be found in Public
Advisories issued by the Weather Prediction Center beginning at 10
PM CDT, under AWIPS header TCPAT4, WMO header WTNT34 KWNH, and on
the web at http://www.wpc.ncep.noaa.gov.

$$
Forecaster Brown

[cycloneye]

Tropical Storm Kate Discussion Number 11
NWS National Hurricane Center Miami FL AL102021
500 PM AST Mon Aug 30 2021

The low-level center of Kate is exposed in visible satellite imagery
this afternoon. Its deep convection collapsed late this morning, and
the sheared tropical cyclone is now only producing a small area of
convection over 60 n mi east of its center. A partial 1321 UTC
ASCAT-B pass still showed numerous 30-kt wind vectors in the eastern
semicircle, even with little to no active convection. The initial
intensity is conservatively lowered to 35 kt for this advisory.

The subtropical jet stream across the central Atlantic will continue
to impart strong west-northwesterly vertical wind shear on Kate
during the next day or so. If the struggling tropical cyclone can
survive these hostile conditions, some modest strengthening could
occur later this week over warm SSTs of 28 deg C or so. However, the
lack of mid-level moisture in the surrounding environment may limit
convective development even under these more favorable conditions,
and there is no guarantee that Kate will survive that long. In fact,
simulated satellite imagery from the GFS and ECMWF suggest that Kate
may continue to only produce sporadic bursts of convection over the
next couple of days, which jeopardizes its chances of surviving
through the week. The official NHC intensity forecast has been
adjusted downward based on the latest guidance trends and the
uncertainties discussed above. Minor fluctuations in intensity could
occur over the next 24-36 h as convective pulsing causes the
cyclone's intensity to hover around tropical-storm-force strength.

Kate is moving a little faster toward the north, or 355/9 kt, within
a weakness in the subtropical ridge. A northward motion is expected
to continue through early Tuesday. The subtropical ridge is expected
to become reestablished over the central Atlantic Tuesday night into
Wednesday, which should turn Kate toward the northwest through
midweek. Thereafter, Kate is forecast to accelerate northward or
north-northeastward ahead of an approaching deep-layer trough that
will move across the western Atlantic late this week. Assuming Kate
is still around by day 5, the cyclone is forecast to become absorbed
by a larger extratropical low near Atlantic Canada.


FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 22.7N 50.9W 35 KT 40 MPH
12H 31/0600Z 23.7N 50.7W 30 KT 35 MPH
24H 31/1800Z 24.7N 50.7W 30 KT 35 MPH
36H 01/0600Z 25.8N 51.1W 35 KT 40 MPH
48H 01/1800Z 27.0N 52.1W 35 KT 40 MPH
60H 02/0600Z 28.4N 53.5W 40 KT 45 MPH
72H 02/1800Z 30.1N 54.7W 40 KT 45 MPH
96H 03/1800Z 34.5N 55.0W 40 KT 45 MPH
120H 04/1800Z...DISSIPATED

$$
Forecaster Reinhart

[Sciencerocks]

[aspen]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

[AlphaToOmega]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

I do not believe the NHC has ever downgraded a storm to a depression.

[zhukm29]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

The ASCAT pass this morning was enough justification for this being named, and it met the criteria regardless of whether it goes poof in the next few days. However, it would be nice for Kate to make it past the shear, not only to generate more ACE for the basin, but also to potentially enhance the weakness to pull future Larry out to sea.

[storminabox]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

I do not believe the NHC has ever downgraded a storm to a depression.

What do you mean? They've done that MANY times...

[AlphaToOmega]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

I do not believe the NHC has ever downgraded a storm to a depression.

What do you mean? They've done that MANY times...

I meant at peak intensity

[Hammy]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

ASCAT showed 40kt so no justification not to name, though in all likelihood it should be applied to the 6-12z portions of the track given when the pass was.

[cycloneye]

Tropical Storm Kate Discussion Number 12
NWS National Hurricane Center Miami FL AL102021
1100 PM AST Mon Aug 30 2021

Kate is a strongly sheared and poorly organized tropical cyclone.
Satellite images show an exposed low-level center with a few patches
of deep convection on the system's east side. The latest Dvorak
classifications range from 25-35 kt, and the initial intensity is
held at a possibly generous 35 kt for this advisory. Unfortunately,
ASCAT missed the circulation this evening.

Strong west-northwesterly shear of about 30 kt is expected to
persist into early Tuesday, and that could cause some weakening in
the short term. Although the shear is expected to lessen after
that, Kate will be moving into a drier and more stable airmass. None
of the intensity models show much strengthening, and the global
models suggest that Kate could dissipate sometime within the next
couple of days. The official forecast is again nudged downward and
generally shows little change in strength during the next 4 days.
Kate, or its remnants, are likely to merge with an extratropical low
and associated front in 4 to 5 days.

The tropical storm has moved little during the past few hours, but a
12-hour motion yields an estimate of 360/5 kt. The storm is moving
toward a weakness in the ridge caused by a deep-layer low over the
North Atlantic, and that motion should continue into Tuesday. By
Wednesday, mid-level ridging building to the northeast of the system
should cause it to turn northwestward. However, another trough
moving eastward over the western Atlantic is expected to cause Kate
to turn northward again toward the end of the week. The NHC track
forecast follows the various consensus aids and is similar to the
previous one.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 22.7N 50.9W 35 KT 40 MPH
12H 31/1200Z 23.6N 50.7W 30 KT 35 MPH
24H 01/0000Z 24.8N 50.9W 30 KT 35 MPH
36H 01/1200Z 26.1N 51.8W 35 KT 40 MPH
48H 02/0000Z 27.6N 52.9W 35 KT 40 MPH
60H 02/1200Z 29.1N 54.0W 35 KT 40 MPH
72H 03/0000Z 30.4N 54.8W 35 KT 40 MPH
96H 04/0000Z 33.9N 54.6W 35 KT 40 MPH
120H 05/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[Sciencerocks]

[MarioProtVI]

The NHC is probably praying this doesn’t poof so there’s actual justification for having it be named. I’m hoping it amounts to something once the shear lets up late tomorrow or Wednesday.

ASCAT showed 40kt so no justification not to name, though in all likelihood it should be applied to the 6-12z portions of the track given when the pass was.

It was applied it seems.

[cycloneye]

[Div][Tropical Storm Kate Discussion Number 13
NWS National Hurricane Center Miami FL AL102021
500 AM AST Tue Aug 31 2021

Kate remains a strongly sheared tropical storm with the associated
deep convection occurring in intermittent bursts in the eastern
semicircle of the cyclone, owing to 850-200-mb west-northwesterly
vertical wind shear of at least 30 kt. The most recent Dvorak
satellite current intensity (CI) estimates remain at 35 kt, and
that is the initial intensity set for this advisory. This intensity
is consistent with an earlier SSMI-S passive microwave satellite
overpass that showed wind speeds of 30-35 kt on the west side of
Kate where no convection/rain was present.

The initial motion estimate is 360/04 kt. Kate's forward motion has
slowed to as low 2 kt during the psst 6 hours, likely due to the
hindering effects of the west-northwesterly shear direction and weak
steering currents since Kate has recently moved into a weakness in
the low- mid-level subtropical ridge. However, the latest NHC track
guidance is in good agreement that the cyclone will begin moving
northward at a slightly faster forward speed as Kate moves through
a break in the ridge. In about 24 hours, a mid-level ridge to the
northeast and east of Kate is forecast to build westward, forcing
the cyclone on a more northwestward trajectory that should continue
through Thursday. By Friday, a mid- to upper-level trough moving
eastward over the western Atlantic is forecast to gradually lift out
Kate toward the north, and accelerate the cyclone toward the
northeast on Saturday. The new NHC forecast track is similar to but
slightly east or right of the previous advisory track, and lies near
the left edge of the tightly packed simple- and corrected-consensus
track-model envelope.

The intensity forecast is not as straightforward as the track
forecast. The aforementioned hostile shear conditions are predicted
by the regional and global models, especially the ECMWF model, to
gradually abate over the next 18-24 hours, with the magnitude of the
shear to decrease to less than 10 kt by 24-36 hours when Kate will
be moving over 28.5 deg C water temperatures. If Kate can survive
the next 18 hours or so, which is possible since the 850-300-mb
shear is much less at only 10-15 kt, then some restrengthening could
occur, especially in the 24-48-hour period when the cyclone will be
located underneath a small upper-level anticyclone. Countering that,
however, is the somewhat dry air (near-50-percent humidity) in the
mid-levels of the atmosphere that could limit the formation of
inner-core convection. Thus for now, the new official intensity
forecast remains similar to the previous advisory, which shows Kate
remaining as a low-end tropical storm through the 96-hour period.
This scenario is consistent with the IVCN and HCCA intensity
consensus models. On day 5, Kate is forecast to dissipate when the
cyclone or its remnants are expected to merge with an extratropical
low and associated frontal system.

FORECAST POSITIONS AND MAX WINDS

INIT 31/0900Z 23.0N 50.9W 35 KT 40 MPH
12H 31/1800Z 23.9N 50.9W 35 KT 40 MPH
24H 01/0600Z 25.2N 51.5W 35 KT 40 MPH
36H 01/1800Z 26.6N 52.4W 35 KT 40 MPH
48H 02/0600Z 28.3N 53.4W 35 KT 40 MPH
60H 02/1800Z 29.9N 54.2W 35 KT 40 MPH
72H 03/0600Z 31.5N 54.8W 35 KT 40 MPH
96H 04/0600Z 35.1N 53.6W 35 KT 40 MPH
120H 05/0600Z...DISSIPATED

$$
Forecaster Stewart
/Div]

[aspen]

Down to a TD. What a pathetic storm, especially for a name that has had multiple instances of being a major.

[AlphaToOmega]

Down to a TD. What a pathetic storm, especially for a name that has had multiple instances of being a major.

It was impressive for a storm battling 30 knots of wind shear.

[Blown Away]

Kate on life support... Look at that shear blast across the LLC, cool.

[SecondBreakfast]

I deeply appreciate this my namesake storm, as I too, am highly disorganized in the mid-Atlantic region.

[xironman]

It just shot out an outflow boundary that seems to about have killed the spin.

[Sciencerocks]