EPAC: ALVIN - Remnants

[Tailspin]

Indeed it was a short life as a cane. Weakening fast.

[zeehag]

it seems the ocean off cabo corrientes area has provided the right conditions for intensification.
they all strengthen in that area.
thankfully the beautiful lil darling is open ocean cane.
somehow these are overlooked..that is fine until they make landfall, see willa, 2018, patricia 2015..both small lil icepicks that make pain on land but are fun to watch develop in open ocean.

[Kingarabian]

I guess it didn't have 12 hours lett of favorable conditions when it becsme a hurricane. Made it just in time. Let's see how long it survives the shear and dry air.

[cycloneye]

Tropical Storm Alvin Discussion Number 13
NWS National Hurricane Center Miami FL EP012019
200 PM PDT Fri Jun 28 2019

Alvin is rapidly weakening due to motion over sea surface
temperatures of 23-24C and increasing southwesterly vertical wind
shear, with the low-level center now partly exposed at the southern
edge of the weakening convective mass. The initial intensity is
reduced to 45 kt based on a blend of recent ASCAT data and
subjective satellite intensity estimates. Continued rapid
weakening is expected, and Alvin is forecast to become a remnant low
in about 24 h and dissipate completely after 36 h.

The initial motion is 310/13. The cyclone should continue
generally northwestward for the next 12-18 h due to flow around a
mid-level ridge to the north. After that time, the weakening and
increasingly shallow system should turn west-northwestward as the
low-level winds become the predominant steering mechanism.

FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 19.7N 118.6W 45 KT 50 MPH
12H 29/0600Z 20.7N 120.0W 35 KT 40 MPH
24H 29/1800Z 21.5N 121.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 30/0600Z 22.0N 123.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 30/1800Z...DISSIPATED

$$
Forecaster Beven

[NotSparta]

ASCAT pass from around 2 hrs ago shows that the circulation is getting less organized

[cycloneye]

Tropical Storm Alvin Discussion Number 14
NWS National Hurricane Center Miami FL EP012019
800 PM PDT Fri Jun 28 2019

Alvin has very little, if any, remaining deep convection, as strong
shear and a cooler ocean have been taking their toll. The
current intensity estimate is a somewhat uncertain 35 kt, which
assumes a steady weakening since the last scatterometer-based
estimate. Since the environment should remain hostile, Alvin is
likely to degenerate into a remnant low on Saturday.

The motion continues northwestward at a slower forward speed, or
310/11 kt. A mid-level ridge to the north and northeast of the
cyclone should steer the system northwestward during the early part
of the forecast period. Afterwards, the weakening and increasingly
shallow cyclone is expected to turn westward following the
low-level flow. The official track forecast is similar to the
dynamical model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 29/0300Z 20.1N 119.3W 35 KT 40 MPH
12H 29/1200Z 20.8N 120.4W 30 KT 35 MPH
24H 30/0000Z 21.1N 121.7W 25 KT 30 MPH...POST-TROP/REMNT LOW
36H 30/1200Z 21.3N 123.1W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 01/0000Z...DISSIPATED

$$
Forecaster Pasch

[TorSkk]

Tropical Depression Alvin Discussion Number 15
NWS National Hurricane Center Miami FL EP012019
200 AM PDT Sat Jun 29 2019

Alvin has become a swirl of low and mid-level clouds as strong
shear and cooler waters have caused a rapid demise of the tropical
cyclone. The initial intensity has been lowered to 25 kt, and is
based on the latest Dvorak T-numbers. The hostile environmental
conditions should continue to cause the cyclone to weaken today,
and the system should degenerate into a remnant low later this
morning.

As expected, Alvin has slowed down and turned west-northwestward,
with an initial motion estimate of 290/7 kt. Now that Alvin has
become a vertically shallow system, a slow westward to west-
northwestward motion within the low-level trade wind flow is
forecast until dissipation occurs. The NHC forecast track lies
along the southern edge of the guidance envelope and is in best
agreement with the latest ECMWF.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 20.3N 119.9W 25 KT 30 MPH
12H 29/1800Z 20.6N 121.0W 20 KT 25 MPH...POST-TROP/REMNT LOW
24H 30/0600Z...DISSIPATED

$$
Forecaster Brown

[cycloneye]

...ALVIN DECAYS INTO A REMNANT LOW...


SUMMARY OF 800 AM PDT...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...20.7N 120.5W
ABOUT 695 MI...1120 KM W OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...NW OR 306 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

[1900hurricane]

The developing core looks pretty good, but such small systems are notoriously fragile at times. The small size may help shield it against dry air, but any shear (especially mid-level) could take it down in a hurry.

Totally ignorant and out of sync again but...Why exactly would a smaller storm be less vulnerable to dry air? Does the dry air tend to flow around it as opposed to into it?

Somewhat. A tropical cyclone is really just a heat engine. Bigger ones require more air to run and therefore more inflow over a larger footprint. A very small system like Alvin doesn't need nearly as much air, meaning it's less likely to pull from somewhere in the surroundings that would have dry air unless it was forcibly injected by shear. Sometimes you'll see huge storms ingest dry air from over 10º away despite a very moist surrounding environment but a small storm seemingly bathing in it be totally fine.

[storm_in_a_teacup]

The developing core looks pretty good, but such small systems are notoriously fragile at times. The small size may help shield it against dry air, but any shear (especially mid-level) could take it down in a hurry.

Totally ignorant and out of sync again but...Why exactly would a smaller storm be less vulnerable to dry air? Does the dry air tend to flow around it as opposed to into it?

Somewhat. A tropical cyclone is really just a heat engine. Bigger ones require more air to run and therefore more inflow over a larger footprint. A very small system like Alvin doesn't need nearly as much air, meaning it's less likely to pull from somewhere in the surroundings that would have dry air unless it was forcibly injected by shear. Sometimes you'll see huge storms ingest dry air from over 10º away despite a very moist surrounding environment but a small storm seemingly bathing in it be totally fine.

That's really cool to know. Thanks.