Tropical Storm Oscar

[Somerset Squall]

The fifteenth tropical depression of the season has formed midway between the Cape Verdes and the Lesser Antilles. The depression is not all well organised, with multiple circulations and the majority of the convection located in a loose band. Shear and dry air are affecting 15L, preventing strengthening. 15L has a small chance of becoming a tropical storm prior to dissipation in the next 48hrs. 15L is moving northwestwards but will accelerate northeastwards over the next day ahead of a large extatropical low to the west which will ultimately bring 15L to an early death.

[JonMillar]

Now Tropical Storm Oscar

000

WTNT45 KNHC 040257

TCDAT5

TROPICAL STORM OSCAR DISCUSSION NUMBER 3

NWS NATIONAL HURRICANE CENTER MIAMI FL AL152012

1100 PM AST WED OCT 03 2012

THE CLOUD PATTERN OF THE CYCLONE HAS MORPHED INTO A LARGE CLUSTER OF

COLD-TOPPED CONVECTION THAT HAS BEEN INCREASING IN INTENSITY AND

COVERAGE DURING THE PAST SEVERAL HOURS. HOWEVER...THE LOW-LEVEL

CENTER REMAINS EXPOSED ABOUT 60 N MI WEST OF THE NEAREST DEEP

CONVECTION AS A CONSEQUENCE OF MODERATE SOUTHWESTERLY SHEAR. AT

0000 UTC...DVORAK T-NUMBERS WERE 2.0 AND 2.5 FROM SAB AND TAFB...

RESPECTIVELY...AND A 0030 UTC ASCAT PASS INDICATED SEVERAL

UNCONTAMINATED 35 KT WIND BARBS ABOUT 100 N MI EAST OF THE CENTER.

BASED PRIMARILY ON THE ASCAT PASS...THE SYSTEM HAS BEEN UPGRADED TO

TROPICAL STORM OSCAR WITH A CONSERVATIVE INTENSITY ESTIMATE OF 35

KT. OSCAR IS ON THE CUSP OF ENTERING AN EVEN HIGHER SHEAR

ENVIRONMENT IN THE NEXT 12-24 HOURS...WHICH SHOULD PRECLUDE

SIGNIFICANT INTENSIFICATION. THE GLOBAL MODELS DEPICT OSCAR OPENING

UP INTO A TROUGH AND THEN LOSING ITS IDENTITY AHEAD OF A COLD FRONT

IN 36-48 HOURS. THE OFFICIAL FORECAST IS SLIGHTLY HIGHER THAN THE

PREVIOUS ONE...BUT STILL SHOWS DISSIPATION IN 48 HOURS.

THE FORWARD SPEED OF OSCAR HAS SLOWED SOME IN RECENT HOURS...AND THE

INITIAL MOTION ESTIMATE IS NOW 335/10. STEERED BY THE FLOW IN

BETWEEN A MID-LEVEL RIDGE NORTH OF THE CAPE VERDE ISLANDS AND A

MID-/UPPER-LEVEL TROUGH NORTHEAST OF THE LESSER ANTILLES...OSCAR

SHOULD GRADUALLY TURN NORTHWARD DURING THE NEXT 12 HOURS OR SO AS

IT DECELERATES FURTHER. AFTER THAT...THE CYCLONE SHOULD BECOME

EMBEDDED IN A STRONG AND DEEP-LAYER WESTERLY FLOW SOUTH OF A

LARGE MID-/UPPER-LEVEL CYCLONE OVER THE NORTHEAST ATLANTIC...WHICH

IS EXPECTED TO RESULT IN A SHARP RECURVATURE AND A NORTHEASTWARD

ACCELERATION. ONLY SMALL ADJUSTMENTS WERE MADE TO THE PREVIOUS

FORECAST THROUGH 24 HOURS...WITH THE TRACK SHIFTED A BIT TOWARD THE

RIGHT PRIOR TO DISSIPATION...WHICH IS IN AGREEMENT WITH THE

DYNAMICAL MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 19.3N 42.2W 35 KT 40 MPH

12H 04/1200Z 20.5N 42.5W 40 KT 45 MPH

24H 05/0000Z 22.0N 41.4W 40 KT 45 MPH

36H 05/1200Z 23.8N 39.4W 40 KT 45 MPH

48H 06/0000Z...DISSIPATED

$$

FORECASTER KIMBERLAIN

[Somerset Squall]

Oscar has strengthened a little today but is a sheared storm. Sustained winds have reached 40kts, and Oscar has likely peaked. Even stronger shear lies ahead, and the large extatropical low will very soon swallow Oscar whole.

[Chris W]

Looks from the forecast track like extratropical Oscar will come for us from the south west, potentially bringing more tropical precipitation with him - as if we need any more (after Nadine's offspring)! A few days off at least however, so it could change.

[Somerset Squall]

Oscar has become a little stronger; sustained winds are now 45kts. Despite this, Oscar hasn't long left, as it is forecst to be absorbed by the large extratropical low within the next 24hrs. Oscar coninues to be sheared, with the majority of the convection residing west of the centre.

[Somerset Squall]

Oscar no longer has a closed circulation so advisories have ceased as Oscar ceases to be a tropical cyclone. The remnant energy will be absorbed by a front tonight.