ATL: ALBERTO - Post-Tropical

[cycloneye]

[stormhunter7]

great discussion by FORECASTER BRENNAN!

[cycloneye]

TROPICAL STORM ALBERTO DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012012
500 PM EDT SAT MAY 19 2012

SATELLITE...RADAR...AND SURFACE DATA INDICATE THAT THE SMALL SURFACE
LOW LOCATED OFF THE COAST OF SOUTH CAROLINA HAS ACQUIRED THE
CHARACTERISTICS OF A TROPICAL CYCLONE. ORGANIZED DEEP CONVECTION
HAS BEEN PERSISTENT OVER THE CENTER FOR MORE THAN 18 HOURS...AND
THE CIRCULATION CENTER HAS BEEN MOVING SOUTH AWAY FROM AN AIRMASS
BOUNDARY THAT EXTENDS ROUGHLY ALONG 33N. BASED ON AN ASCAT PASS
FROM AROUND 1530 UTC...THE INITIAL INTENSITY IS SET AT 40 KT.
ALBERTO IS SITUATED IN A MARGINAL THERMODYNAMIC ENVIRONMENT FOR
STRENGTHENING...WITH A MARKEDLY DRY CONTINENTAL AIRMASS TO ITS NORTH
AND WEST OVER THE EASTERN CAROLINAS. GIVEN THIS...ONLY MODEST
INTENSIFICATION IS EXPECTED DESPITE THE CYCLONE BEING OVER
THE RELATIVELY WARM GULF STREAM. ALBERTO IS EXPECTED TO BECOME
EXTRATROPICAL BY 96 HOURS...AND SHOULD DISSIPATE BY DAY 5. THE NHC
INTENSITY FORECAST IS A BLEND OF THE MORE AGGRESSIVE STATISTICAL
GUIDANCE AND THE WEAKER DYNAMICAL MODELS.

THE LOW-LEVEL CIRCULATION IS A BIT TO THE EAST OF THE COLDEST CLOUD
TOPS AND THE CIRCULATION CENTER SEEN ON RADAR...AND THE INITIAL
MOTION ESTIMATE IS 220/03. THE SYNOPTIC ENVIRONMENT IS COMPLEX...AS
ALBERTO IS IN A REGION OF WEAK STEERING FLOW WITHIN A BROAD
MID/UPPER-LEVEL TROUGH. THE NHC FORECAST SHOWS A SLOW SOUTHWESTWARD
MOTION OVER THE NEXT DAY OR SO DUE TO THE STRONG NORTHEASTERLY FLOW
BETWEEN A SURFACE RIDGE EAST OF THE APPALACHIANS AND A LARGER
EXTRATROPICAL LOW CENTERED NEAR 36N/72W. AS THAT LOW MOVES WESTWARD
AND WEAKENS BY SUNDAY NIGHT...ALBERTO IS EXPECTED TO TURN NORTHWARD
AND THEN ACCELERATE NORTHEASTWARD AFTER 48 HOURS AS A SHORTWAVE
TROUGH MOVES INTO THE EASTERN UNITED STATES AND THE STEERING FLOW
BECOMES SOUTHWESTERLY. GIVEN THE SMALL SIZE OF ALBERTO AND THE
COMPLEX STEERING PATTERN...IT IS NOT SURPRISING THAT THE TRACK
MODEL GUIDANCE SHOWS A LARGE AMOUNT OF SPREAD...BOTH IN TERMS OF
HOW FAR SOUTH AND WEST ALBERTO WILL MOVE...AND HOW SHARP THE TURN
TOWARD THE NORTHEAST WILL BE. THE NHC TRACK FORECAST IS GENERALLY
CLOSE TO THE TVCA MULTI-MODEL CONSENSUS...AND IS OF VERY LOW
CONFIDENCE.

A TROPICAL STORM WATCH COULD BE REQUIRED FOR A PORTION OF THE COAST
OF THE CAROLINAS THIS EVENING.

ALBERTO IS EARLIEST-FORMING TROPICAL STORM IN THE ATLANTIC BASIN
SINCE ANA IN 2003. THIS IS ALSO THE FIRST TIME THAT A TROPICAL
STORM HAS FORMED BEFORE THE OFFICIAL START OF THE HURRICANE SEASON
IN BOTH THE ATLANTIC AND EAST PACIFIC BASINS.


FORECAST POSITIONS AND MAX WINDS

INIT 19/2100Z 32.2N 77.7W 40 KT 45 MPH
12H 20/0600Z 31.9N 78.1W 45 KT 50 MPH
24H 20/1800Z 31.7N 78.5W 45 KT 50 MPH
36H 21/0600Z 31.9N 78.9W 45 KT 50 MPH
48H 21/1800Z 32.7N 78.5W 45 KT 50 MPH
72H 22/1800Z 34.5N 75.5W 45 KT 50 MPH
96H 23/1800Z 37.5N 72.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 24/1800Z...DISSIPATED

$$
FORECASTER BRENNAN

[FutureEM]

Why is there a TS Watch for part of Long Island?

[thegreatdr]

Feel much better about this discussion now...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
203 PM EDT SUN MAY 13 2012

VALID 12Z WED MAY 16 2012 - 12Z SUN MAY 20 2012

...COASTAL LOW/NOR'EASTER POSSIBLE NEAR THE CAROLINAS NEXT
WEEKEND...

OUTSIDE THE 00Z CANADIAN GUIDANCE BEYOND FRIDAY MORNING...THE
AVAILABLE DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE IS IN VERY GOOD
AGREEMENT CONCERNING THE EXPECTED FLOW PATTERN. TROUGHING BECOMES
ESTABLISHED ACROSS THE INTERMOUNTAIN WEST WHILE RIDGING EXISTS
ACROSS THE PLAINS/MIDWEST AND A DEEP CYCLONE MOVES OFFSHORE THE
SOUTHEAST COAST. SINCE THERE WAS SUCH GOOD AGREEMENT...USED A
40/30/30 BLEND OF THE 00Z UKMET/00Z GFS/00Z ECMWF THROUGH FRIDAY
BEFORE SWITCHING TO A 50/50 BLEND/COMPROMISE OF THE 00Z GFS AND
00Z ECMWF SOLUTIONS. THIS PREFERENCE LED TO GOOD CONTINUITY.

THE DEEP CYCLONE/NOR'EASTER FORECAST OFFSHORE THE SOUTHEAST COAST
THIS WEEKEND HAS A CHANCE TO BECOME A HYBRID SYSTEM AS IT HOVERS
NEAR THE WARM GULF STREAM WATERS FROM FRIDAY INTO EARLY THE
FOLLOWING WEEK. EVEN IF IT REMAINS COLD CORE...THE SYSTEM SHOULD
LEAD TO LOWERED PRESSURES/DISTURBED WEATHER ACROSS THE WESTERN
CARIBBEAN LATE IN THE PERIOD NEAR THE BASE OF ITS UPPER
TROUGH/COLD FRONT...NORMALLY A PROBLEM WHEN A DEEP LAYERED CYCLONE
FORMS BETWEEN THE SOUTHEAST AND BERMUDA. HEAVY COMMA HEAD
RAINS/WINDY CONDITIONS ARE POSSIBLE NEAR THE
CAROLINA/GEORGIA/NORTHEAST FLORIDA COAST IF THE SYSTEM TAKES A
MORE COASTAL ROUTE AS SEEN IN THE 00Z ECMWF. IF IT DEVELOPS AND
STAYS FARTHER OFFSHORE...IT COULD EVOLVE INTO A WILDFIRE CONCERN
FOR SOUTH CAROLINA/GEORGIA/NORTHERN FLORIDA WHICH ARE WITHIN THEIR
ANNUAL SPRING DROUGHT...SIMILAR TO THE SITUATION SEEN DURING
SUBTROPICAL STORM ANDREAS DEVELOPMENT DURING EARLY MAY 2007. THE
POTENTIAL DEVELOPMENT AS SEEN BY ECMWF OVER THE PAST SEVERAL RUNS
IS DIFFERENT THAN THAT OF 2007 EVOLUTION OF ANDREAS...BUT THE
FINAL DEVELOPMENT OF ANDREAS INTO ITS SUBTROPICAL FORM IS SIMILAR
IN THE MID LEVEL H500 FLOW OF THIS EVENT.

VELOCITY POTENTIAL ANOMALIES OF GFS/ECMWF/CMC CONTINUE TO INDICATE
A FAVORABLE ENVIRONMENT FOR TROPICAL DEVELOPMENT IN THE EASTERN
PACIFIC/WESTERN CARRIBEAN AND OFF THE U.S. SOUTHEASTERN SEABOARD.
THE EASTERN PACIFIC ALREADY HAS A SYSTEM READY TO GO AND WILL
LIKELY BE AT LEAST A TROPICAL DEPRESSION IN THE NEXT DAY OR SO.
SEE NHC DISCUSSIONS. THE ATLANTIC SIDE OFF THE SOUTHEASTERN
SEABOARD ALSO HAS FAVORABLE CONDITIONS AS MENTIONED ABOVE WITH A
LARGE NUMBER OF ECMWF ENSEMBLE MEMBERS SUPPORTING THE OPERATIONAL
RUN WITH THE SYSTEM LATE NEXT WEEK AND WEEKEND. BEYOND THIS TIME
FRAME LONGER TERM RUNS OF GFS HAVE BEEN PRODUCING TROPICAL SYSTEMS
IN THE WESTERN CARRIBEAN WITH AN EXIT NORTH AND NORTHEASTWARD.
THIS IS ANOTHER INDICATION THAT THE MODELS RECOGNIZE FUTURE
FAVORABLE DEVELOPMENT CONDITIONS OR CYCLOGENESIS.

UPDATED MORNING PRELIMS REMAIN SIMILAR TO THE OVERNIGHT PACKAGE
WITH AN ADJUSTMENT OF THE SOUTHEASTERN SEABOARD LOW SOUTHWARD OF
THE EARLY PRELIMS OFF THE SC COAST AS A BETTER FIT TO LAGGED
AVERAGE FORECASTS OF ECMWF AND GFS.

AFTN FINALS REMAIN THE SAME. ADDITIONAL SUPPORT FOR EARLIER PROGS
BY HIRES UKMET OVER CONUS AND ADJACENT WATERS. SOUTHEAST SEABOARD
LOW FORECAST SE OF CAPE FEAR IN GOOD AGREEMENT WITH 00Z ECMWF DAYS
6-7.

ROTH/ROSENSTEIN

[stormhunter7]

A LARGER EXTRATROPICAL LOW CENTERED NEAR 36N/72W.

[KatDaddy]

Welcome back everyone for the 2012 Hurricane Season. Where is the hurricane party going to be.....S2K chatroom???

[stormhunter7]

sent a msg to a friend.. the orange/yellow NYC warning accident on the forecast map should be gone real soon!

ALBERTO IS EARLIEST-FORMING TROPICAL STORM IN THE ATLANTIC BASIN
SINCE ANA IN 2003. THIS IS ALSO THE FIRST TIME THAT A TROPICAL
STORM HAS FORMED BEFORE THE OFFICIAL START OF THE HURRICANE SEASON
IN BOTH THE ATLANTIC AND EAST PACIFIC BASINS.

[JonathanBelles]

The NHC forecast graphics have been re-released with the TS watches removed.

[cycloneye]

The NHC forecast graphics have been re-released with the TS watches removed.

[StormGuy]

Why is there a TS Watch for part of Long Island?

That has to be a mistake.

[OuterBanker]

Did anyone guess May 19 for first named system?

[CrazyC83]

The closest to having both basins having pre-season activity was 1992 before now - a freak of nature Cat 3 in February and a tropical storm in March in the Pacific along with an April subtropical storm in the Atlantic, but that never gained full tropical characteristics.

[lester]

Welcome back everyone for the 2012 Hurricane Season. Where is the hurricane party going to be.....S2K chatroom???

yep as always

[Aric Dunn]

The Atlantic said sorry eastern pacific you going down this season !

[CrazyC83]

How small is this storm? Most of the coastal Carolinas are reporting a few clouds to partly cloudy right now. Hard to notice a tropical storm on their doorstep when it is quite pleasant out.

[KyleEverett]

Impressive midlevels to this system.

[cycloneye]

Did anyone guess May 19 for first named system?

On the poll about when the first named system would form,8 members nailed May and member Cyclenall was close to the date as he said May 15th at 5:00 PM EDT.

viewtopic.php?f=31&t=112525&start=0

[Aric Dunn]

How small is this storm? Most of the coastal Carolinas are reporting a few clouds to partly cloudy right now. Hard to notice a tropical storm on their doorstep when it is quite pleasant out.

marco in 2008 is the world record for smallest with TS extending out 11.5 nm from center vs. alberto with 45nm

http://en.wikipedia.org/wiki/Tropical_S ... %282008%29

[Aric Dunn]

on a side note. the Euro takes it south of thirty north pretty darn close the NE florida in 36 to 48 hours.

http://www.meteo.psu.edu/~gadomski/ECMW ... floop.html