EPAC: ANDRES - Post-Tropical

[Subtrop]

WTPZ41 KNHC 091454
TCDEP1

Tropical Storm Andres Discussion Number 2
NWS National Hurricane Center Miami FL EP012021
900 AM MDT Sun May 09 2021

Although the system lacks well-defined convective banding features,
Dvorak intensity estimates from both TAFB and SAB are 35 kt.
This is consistent with a data T-number based on a shear pattern
with the low-level center displaced within 3/4 degrees to the west
of the edge of the main area of deep convection, as suggested by
recent microwave imagery. Since earlier scatterometer data
indicated that the system was close to tropical storm strength,
and given the latest Dvorak analyses, the cyclone is being named.
Andres is the earliest tropical storm on record in the eastern
North Pacific basin, just beating out Adrian of 2017.
Increasing southwesterly to westerly shear and drier air to the
west of the cyclone should prevent any significant additional
strengthening. The official forecast generally follows the
numerical guidance and shows the system degenerating into a remnant
low in 48 hours, as in the previous advisory.

The initial motion is slowly northwestward, or 325/5. Andres
should move along the southwestern side of a low- to mid-level
ridge for the next couple of days and turn westward in the
low-level flow as an increasingly shallow circulation. The
official track forecast is on the southern side of the model
guidance suite. This also close to the latest latest corrected
consensus, or HCCA, track.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 14.1N 107.9W 35 KT 40 MPH
12H 10/0000Z 14.8N 108.4W 35 KT 40 MPH
24H 10/1200Z 15.4N 108.9W 35 KT 40 MPH
36H 11/0000Z 15.9N 109.5W 30 KT 35 MPH
48H 11/1200Z 16.2N 110.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 12/0000Z 16.5N 111.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 12/1200Z 16.4N 112.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 13/1200Z 16.3N 115.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
120H 14/1200Z...DISSIPATED

$$
Forecaster Pasch

[DorkyMcDorkface]

EPAC made me eat my words this weekend, lol. Had sincere doubts this would develop with an approaching suppressed CCKW but it still managed to do it, and evolved further into a TS in the process. Obviously not the nicest looking system but it's still a neat development regardless.

[aspen]

Oh look, a weak record-breaking pre-season TC in the EPac in a year with a neutral to cool ENSO being likely for ASO.

I’m guessing Andres is a sign we’re in for another lackluster EPac and at least a normally above-average Atlantic.

[Iceresistance]

The map above is showing "No Active Storms' for some reason,maybe because of how early Andres really is!

[Sciencerocks]

Strong shear forcing the convection northeast of the exposed center.

[Yellow Evan]

Oh look, a weak record-breaking pre-season TC in the EPac in a year with a neutral to cool ENSO being likely for ASO.

I’m guessing Andres is a sign we’re in for another lackluster EPac and at least a normally above-average Atlantic.

Considering how relatively rare storms this early are at least untill recently, I’m not convinced it’s correlated with Atlantic activity and Eastern Pacific inactivity. It’s possible the wet Sahel and the cold Nino 1+2 are contributing factors to some of the fast starts we’ve seen recently but that’s the furthest I’m willing to actually go.

[AnnularCane]

Oh look, a weak record-breaking pre-season TC in the EPac in a year with a neutral to cool ENSO being likely for ASO.

I’m guessing Andres is a sign we’re in for another lackluster EPac and at least a normally above-average Atlantic.

Maybe, but probably not much of a sign since the season hasn't started yet.

[MarioProtVI]

Strong shear forcing the convection northeast of the exposed center.

https://imagizer.imageshack.com/img922/8286/hMnkdG.gif

I’m not even sure if it’s completely closed now looking at a loop of it, but it’s very poorly defined and will probably die even sooner then NHC thinks it will.

[NotSparta]

Oh look, a weak record-breaking pre-season TC in the EPac in a year with a neutral to cool ENSO being likely for ASO.

I’m guessing Andres is a sign we’re in for another lackluster EPac and at least a normally above-average Atlantic.

Considering how relatively rare storms this early are at least untill recently, I’m not convinced it’s correlated with Atlantic activity and Eastern Pacific inactivity. It’s possible the wet Sahel and the cold Nino 1+2 are contributing factors to some of the fast starts we’ve seen recently but that’s the furthest I’m willing to actually go.

Early/pre season EPAC activity like this tends to be correlated to a mode poleward ITCZ, which is itself correlated with -ENSO, I believe

[Kingarabian]

Think it's pretty hard to correlate May EPAC activity (or even early season systems) with future state of ENSO. We've seen May systems in +ENSO and -ENSO years. Also seen a Cat.5 Celia hurricane in June 2010, a strong La Nina year. The EPAC is very sensitive to intraseasonal variability, and systems early on are usually a product of such.

[cycloneye]

Think it's pretty hard to correlate May EPAC activity (or even early season systems) with future state of ENSO. We've seen May systems in +ENSO and -ENSO years. Also seen a Cat.5 Celia hurricane in June 2010, a strong La Nina year. The EPAC is very sensitive to intraseasonal variability, and systems early on are usually a product of such.

In other words, an early system does not indicate anything about how the season will be in terms of activity.

[Michele B]

I hope this not a sign of things to come.

[cycloneye]

Tropical Storm Andres Discussion Number 3
NWS National Hurricane Center Miami FL EP012021
300 PM MDT Sun May 09 2021

The convective cloud pattern of Andres is rather ragged-looking at
this time, and the system continues to show little evidence of
banding features. However the cyclone is producing some very cold
cloud tops over the eastern portion of the circulation. A partial
scatterometer pass did not show tropical-storm-force winds, but it
is believed that these could be occuring in the strong convection
to the east of the center. The current intensity estimate remains
at 35 kt in agreement with the latest Dvorak estimates from TAFB
and SAB. The environment ahead of Andres looks very hostile, with
increasing west-southwesterly shear and dry air in the mid- to
lower-troposphere. Therefore, a weakening trend should begin
tomorrow and the system is likely to degenerate into a remnant low
in about 48 hours which is also indicated by the global model
guidance.

The scatterometer observations showed that the center was somewhat
elongated zonally, but it appears to be a little south of the
previously estimated track. Andres should move along the
southwestern periphery of a mid-level ridge for the next day or
so, and then turn westward in 48-60 hours, following the low-level
steering flow. The official track forecast is south of much of the
model guidance on account of the more southward center location.
This is not far from the latest GFS model solution.


FORECAST POSITIONS AND MAX WINDS

INIT 09/2100Z 14.0N 108.5W 35 KT 40 MPH
12H 10/0600Z 14.7N 109.1W 35 KT 40 MPH
24H 10/1800Z 15.2N 109.7W 30 KT 35 MPH
36H 11/0600Z 15.6N 110.2W 30 KT 35 MPH
48H 11/1800Z 15.8N 111.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 12/0600Z 15.9N 112.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 12/1800Z 15.9N 113.5W 20 KT 25 MPH...POST-TROP/REMNT LOW
96H 13/1800Z...DISSIPATED

$$
Forecaster Pasch

[ClarCari]

On a side note, many people in the meteorlogical world have been butchering pronouncing this name about as bad as Isaias lmao. The NHC pronunciation makes it sound like “On-drase” like Drake. But I heard plenty of people pronounce it like “And-dress” like salad dressing lol, “And-dreeese”, or worse “AndrEAS” like San Andreas.
Of course with my hispanic background, we pronounced it similar to the NHC pronunciation, but with an accented “É” and a trilled R.

[USTropics]

Here is some data on May formation of tropical systems in the East Pacific (going back 50 years), and how this correlates to the rest of the season in the East Pacific (and relationship to Atlantic activity for same year). Included are NAO indexes for May and ONI values for April - June. For a system that reaches tropical storm strength in the first 3 weeks of May, there isn't much correlation. However, if an East Pacific system reaches hurricane strength in the month of May, there is more of a correlation of an active EPAC versus inactive Atlantic season.

All systems that formed in East Pacific during the month of May:


Data table for values:

[Yellow Evan]

Blanca 2015 didn't become a TS or hurricane in May so they technically shouldn't count.

[Yellow Evan]

000
WTPZ41 KNHC 100236
TCDEP1

Tropical Storm Andres Discussion Number 4
NWS National Hurricane Center Miami FL EP012021
900 PM MDT Sun May 09 2021

Andres remains a ragged-looking tropical cyclone this evening. The
majority of the deep convection is displaced well to the east of
the low-level center and there is little evidence of banding
features. Dvorak intensity estimates from both SAB and TAFB still
support an intensity of 35 kt, and that value is used as the initial
wind speed for this advisory, although that may be generous given
the recent satellite presentation. Overnight scatterometer data
should provide a better assessment of the cyclone's intensity.

Increasing southwesterly vertical wind shear and dry mid-level air
should cause Andres to begin to weaken overnight or on Monday, if
that weakening trend has not already begun. Andres is forecast to
move into an area of even higher shear by Monday night or early
Tuesday, and this should cause the cyclone to become a remnant low
in about 36 hours. Thereafter, the cyclone is forecast to gradually
spin down and dissipate by day 3 as indicated by the global models.

Andres has moved a little more westerly over the past 12-24 hours
than anticipated, but a longer term motion is northwestward or
305/5 kt. The track guidance insists that the cyclone will gain
more latitude during the next day or so, before it weakens and
becomes vertically shallow. Once that occurs Andres should turn
westward within the low-level flow. The latest NHC track forecast
has been adjusted south and west of the previous track during the
first 12-24 hours, due to the more westward initial position.
Thereafter, it is similar to the previous NHC advisory, and is in
best agreement with the GFS and GFS-ensemble mean models.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0300Z 14.3N 109.0W 35 KT 40 MPH
12H 10/1200Z 14.8N 109.4W 30 KT 35 MPH
24H 11/0000Z 15.4N 109.9W 30 KT 35 MPH
36H 11/1200Z 15.8N 110.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 12/0000Z 15.9N 111.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 12/1200Z 15.9N 112.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 13/0000Z...DISSIPATED

$$
Forecaster Brown

[FireRat]

On a side note, many people in the meteorlogical world have been butchering pronouncing this name about as bad as Isaias lmao. The NHC pronunciation makes it sound like “On-drase” like Drake. But I heard plenty of people pronounce it like “And-dress” like salad dressing lol, “And-dreeese”, or worse “AndrEAS” like San Andreas.
Of course with my hispanic background, we pronounced it similar to the NHC pronunciation, but with an accented “É” and a trilled R.

It's pretty funny because this name is actually the Spanish version of 'Andrew'. So much easier to pronounce in English lol

[cycloneye]

Tropical Storm Andres Discussion Number 5
NWS National Hurricane Center Miami FL EP012021
300 AM MDT Mon May 10 2021

Andres remains a sheared tropical storm with a small ball of deep
convection displaced just east of the partially exposed low-level
center. All three scatterometer passes missed Andres. The initial
intensity remains 35 kt based on consensus subjective Dvorak
satellite intensity estimates of T2.5/35 kt from TAFB and SAB, and
objective intensity estimates of 37 kt and 35 kt from UW-CIMSS ADT
and SATCON, respectively.

The initial motion estimate is 325/04 kt. There are no significant
changes to the previous track forecast of reasoning. The latest NHC
track model guidance continues to show Andres moving slowly
northwestward around the western edge of a deep-layer subtropical
ridge while gradually weakening and becoming more vertically
shallow. The ridge to the north of the cyclone is forecast to
strengthen and build westward over the next few days, which is
expected to gradually nudge Andres west-northwestward on Tuesday and
westward on Wednesday. The new official track forecast is similar to
the previous advisory track, and remains along the southern edge of
the guidance envelope between the GFS and GFS-ensemble mean models,
and the HCCA and GFEX consensus track models.

Despite the ragged looking cloud pattern depicted in infrared
satellite imagery, night-viz and passive microwave satellite data
indicate that the low-level circulation has actually improved a
little since the previous advisory. However, the combination of
increasing southwesterly vertical wind shear and entrainment of
drier and more stable low- to mid-level air from the west and
northwest is expected to induce gradual weakening later today.
Additional weakening is forecast on Tuesday and Wednesday as Andres
moves over cooler sea-surface temperatures, with the cyclone
expected to degenerate into a remnant low on Tuesday and dissipate
by Thursday. The latest NHC intensity forecast is essentially just
and update of the previous advisory, and closely follows a blend of
the IVCN and HCCA intensity consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT 10/0900Z 14.7N 109.1W 35 KT 40 MPH
12H 10/1800Z 15.2N 109.7W 30 KT 35 MPH
24H 11/0600Z 15.6N 110.3W 30 KT 35 MPH
36H 11/1800Z 15.9N 111.1W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 12/0600Z 16.0N 112.2W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 12/1800Z 16.0N 113.3W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 13/0600Z...DISSIPATED

$$
Forecaster Stewart

[Sciencerocks]

000
WTPZ41 KNHC 101448
TCDEP1

Tropical Storm Andres Discussion Number 6
NWS National Hurricane Center Miami FL EP012021
900 AM MDT Mon May 10 2021

Andres continues to battle vertical wind shear this morning. Early
visible satellite imagery indicates the broadened circulation of the
cyclone is exposed and displaced to the southwest of a recent burst
of deep convection. Overall, the convective coverage has noticeably
decreased during the past several hours, with warming infrared cloud
top temperatures noted where a convective band wrapped around the
eastern semicircle overnight. A blend of the objective ADT and
SATCON estimates with subjective Dvorak classifications from SAB and
TAFB supports holding the initial intensity at 35 kt. Hopefully,
scatterometer data will become available this afternoon to better
assess the intensity of Andres.

The center of the cyclone was adjusted a bit northward this morning
based on recent visible imagery, and its estimated motion is now
330/05 kt. A general northwestward motion is expected today as
Andres moves around the western edge of a deep-layer subtropical
ridge. As the cyclone spins down and becomes more vertically
shallow, it should turn more west-northwestward and then westward
under the influence of a building low-level ridge to its north. The
forecast track has been nudged to the right of the previous forecast
to account for the center adjustment, and the new track lies closer
to the reliable consensus aids including HCCA.

Increasing southwesterly vertical wind shear, along with drier and
more stable low- to mid-level air approaching from the west, suggest
a weakening trend is imminent. Andres is expected to become a
tropical depression later today and then continue weakening through
midweek as environmental conditions become increasingly hostile. GFS
and ECMWF simulated satellite imagery suggest the cyclone will
become devoid of convection by tonight, and so this forecast shows
Andres becoming a remnant low by Tuesday morning.


FORECAST POSITIONS AND MAX WINDS

INIT 10/1500Z 15.4N 109.4W 35 KT 40 MPH
12H 11/0000Z 15.8N 109.7W 30 KT 35 MPH
24H 11/1200Z 16.1N 110.2W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 12/0000Z 16.4N 111.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 12/1200Z 16.3N 112.4W 20 KT 25 MPH...POST-TROP/REMNT LOW
60H 13/0000Z 16.2N 113.9W 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 13/1200Z...DISSIPATED

$$
Forecaster Reinhart/Pasch