EPAC: LOWELL - Post-Tropical

[ElectricStorm]

Please become a hurricane so we can have something else to track that isn't affecting land...

[Chris90]

NHC has it @ as a 70MPH TS for 36 hours is a bit odd. It will likely reach hurricane status.

I'm in agreement with you. It's probably a dangerous bet this year, so it's a good thing I don't have money on it, but I think Lowell can probably get to about 75kts.

[cycloneye]

Tropical Storm Lowell Discussion Number 8
NWS National Hurricane Center Miami FL EP172020
800 AM PDT Tue Sep 22 2020

Lowell's satellite appearance has improved slightly over the past
several hours, with the mass of deep convection becoming a little
more symmetrical. However, the center still appears to be near the
northeastern edge of this convection. A blend of the latest
satellite intensity estimates from both TAFB and SAB suggest that
the cyclone has strengthened, and the initial intensity has been
increased to 45 kt. The north-northeasterly shear is expected to
persist for the next few days, and the cyclone is only expected to
remain over waters warmer than 26 degrees C for the 24-36 h.
Therefore, only some slow strengthening is expected during the
next day or so. At around 72 h, Lowell is expected to begin moving
over waters of around 25 degrees C while entering a drier and more
stable airmass. These conditions should cause the cyclone to weaken.
Late in the forecast period, model guidance suggests that Lowell
will encounter strong westerly wind shear. There is a possibility
that the cyclone could lose its deep convection once that shear sets
in, and although the latest advisory does not indicate it, Lowell
could degenerate into a remnant low by the end of the 5-day
forecast period. The latest NHC intensity forecast is near the
corrected consensus HCCA.

The storm is estimated to be moving 290/11 kt, on the southern side
of a subtropical ridge. This motion should continue through
Wednesday, followed by a turn to the west as the ridge changes its
orientation slightly. The latest NHC track forecast is near the
previous one through 24 h and is only a little north of it
thereafter due to a shift in the track guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 22/1500Z 18.4N 116.6W 45 KT 50 MPH
12H 23/0000Z 19.0N 118.2W 45 KT 50 MPH
24H 23/1200Z 19.6N 120.0W 50 KT 60 MPH
36H 24/0000Z 20.1N 121.8W 55 KT 65 MPH
48H 24/1200Z 20.4N 123.4W 55 KT 65 MPH
60H 25/0000Z 20.5N 125.2W 55 KT 65 MPH
72H 25/1200Z 20.6N 127.0W 50 KT 60 MPH
96H 26/1200Z 20.6N 131.0W 40 KT 45 MPH
120H 27/1200Z 20.6N 135.5W 35 KT 40 MPH

$$
Forecaster Latto

[cycloneye]

Tropical Storm Lowell Discussion Number 9
NWS National Hurricane Center Miami FL EP172020
200 PM PDT Tue Sep 22 2020

Lowell has been undergoing a bursting pattern today, with the
original mass dissipating and a new one developing in its place.
This is typical of sheared tropical cyclones. Just in the past
couple of hours, visible satellite imagery has shown a low-level
swirl ejecting to the northwest from the deep convection. Based on
the center position from an ASCAT overpass around 1700 UTC, the
exposed swirl may indeed be the primary center of the cyclone. This
same ASCAT overpass showed peak winds of 37 kt, and based on the
evolution of the cyclone's structure in the past couple of hours,
the initial intensity is being lowered to 40 kt. The northeasterly
shear causing the developmental issues for Lowell may abate somewhat
in a day or so. This may provide the cyclone with an opportunity for
some strengthening before it reaches cooler waters in a couple of
days. After 72 h, Lowell is forecast to begin moving over waters of
24-25 degrees C, and enter an increasingly hostile environment with
strong westerly shear and mid-level relative humidity values around
30 percent by the end of the forecast period. These conditions
should cause the cyclone to weaken starting late this week. There is
a possibility that the cyclone could lose its deep convection late
in the forecast period, and although the latest advisory does not
indicate it, Lowell could degenerate into a remnant low by day 5.
The latest NHC intensity forecast is near the various intensity
consensus values.

The initial motion of the cyclone is 295/12 kt, but this is
uncertain due to the recent northwestern motion of the low-level
center. A general west-northwest motion is expected through
Wednesday as Lowell moves south of a subtropical ridge. A turn to
the west is expected Wednesday night as the ridge changes its
orientation slightly. The latest NHC track forecast is little
changed from the previous one and is near the tightly clustered
track guidance.


FORECAST POSITIONS AND MAX WINDS

INIT 22/2100Z 19.2N 117.9W 40 KT 45 MPH
12H 23/0600Z 19.7N 119.6W 40 KT 45 MPH
24H 23/1800Z 20.0N 121.2W 40 KT 45 MPH
36H 24/0600Z 20.4N 122.9W 45 KT 50 MPH
48H 24/1800Z 20.6N 124.6W 50 KT 60 MPH
60H 25/0600Z 20.7N 126.4W 50 KT 60 MPH
72H 25/1800Z 20.7N 128.2W 50 KT 60 MPH
96H 26/1800Z 20.7N 132.3W 40 KT 45 MPH
120H 27/1800Z 20.7N 136.2W 35 KT 40 MPH

$$
Forecaster Latto

[aspen]

Yet another EPac under-achiever. The NHC was right to not forecast a hurricane.

[Yellow Evan]

000
WTPZ42 KNHC 250839
TCDEP2

Tropical Storm Lowell Discussion Number 19
NWS National Hurricane Center Miami FL EP172020
1100 PM HST Thu Sep 24 2020

Only a small area of deep convection is lagging about 100 n mi east
of Lowell's center, but a recent scatterometer pass showed that
maximum winds are still around 35 kt. The areal coverage of
Lowell's convection and its distance from the center already put it
on the margins of what is considered organized deep convection.
Cold waters and increasing westerly to southwesterly shear
over the next 24 hours should finally do the convection in, causing
Lowell to lose tropical cyclone status on Friday. Even stronger
shear is forecast to cause the remnant low to gradually weaken
through the end of the 5-day forecast period.

Fixes based on infrared and microwave satellite imagery indicate
that Lowell has begun to lose some latitude, and the initial motion
is just south of due west (265/10 kt). The south-of-due-west
motion is forecast to continue for the next 2-3 days courtesy of
strong low- to mid-level ridging north of Lowell. The remnant low
should then gradually turn toward the west-northwest and slow down
by the end of the forecast period when it reaches a break in the
ridge ahead of a cold front north of the Hawaiian Islands. The new
NHC track forecast is similar to the previous prediction and
remains embedded within the tightly clustered guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 25/0900Z 21.6N 128.0W 35 KT 40 MPH
12H 25/1800Z 21.5N 129.8W 35 KT 40 MPH
24H 26/0600Z 21.4N 132.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 26/1800Z 21.3N 135.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
48H 27/0600Z 21.2N 137.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 27/1800Z 21.1N 140.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 28/0600Z 21.1N 142.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 29/0600Z 21.5N 146.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 30/0600Z 22.7N 149.5W 20 KT 25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg