South Atlantic Disturbance (Brazil: 18S 38W)

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An area of disturbed weather has formed off the coast of Brazil, near 18S 38W. This disturbance has the potential to develop into subtropical or tropical depression early next week. Satellite winds estimates from the WindSat instrument show an elongated area of converging winds, but no organized surface circulation. Satellite loops show little organization to the cloud pattern, and only limited heavy thunderstorm activity. Wind shear over the region is about 20 knots, which is rather high, and should keep any development slow. Sea surface temperatures are about 28°C, about 1°C above average, and plenty warm enough to support a tropical storm.

Several global models, such as the ECMWF, UKMET, and NOGAPS models have been developing this system in recent runs. Phase space diagrams form Florida State University confirm that this storm is expected to primarily be a warm-cored system, meaning it will probably be classifiable as a subtropical or tropical storm if it attains surface wind speeds of at least 39 mph. The system is capable of bringing heavy rains to the Brazilian coast while it is in its formative stages over the next few days, but I doubt that these rains would be heavy enough to cause flooding concerns. By Monday, the storm should be headed southwards or south-eastwards out to sea, and it appears unlikely that Brazil would see tropical storm-force winds of 39+ mph from this system. I give this storm a low (< 30% chance) of developing into a tropical or subtropical depression by Sunday.

Jeff Masters

http://www.wunderground.com/blog/JeffMasters/article.html?entrynum=1442

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ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/

BEGIN

NHC_ATCF

invest_sl802010.invest

FSTDA

R

U

040

010

0000

201003052133

NONE

NOTIFY=ATRP

END

TEST, SL, Q, , , , , 80, 2010, TD, O, 2010030518, 9999999999, , , , , , METWATCH, , SL802010

SL, 80, 2010030500, , BEST, 0, 181S, 253W, 20, 1007, TD, 0, , 0, 0, 0, 0,

SL, 80, 2010030506, , BEST, 0, 187S, 270W, 20, 1007, TD, 0, , 0, 0, 0, 0,

SL, 80, 2010030512, , BEST, 0, 194S, 284W, 20, 1007, TD, 0, , 0, 0, 0, 0,

SL, 80, 2010030518, , BEST, 0, 200S, 300W, 20, 1009, TD,

[Somerset Squall]

UK Met still keen on this one becoming a tropical storm, sea temps are certainly high enough at 28C:

MET OFFICE TROPICAL CYCLONE GUIDANCE FOR NORTH-EAST PACIFIC

AND ATLANTIC

GLOBAL MODEL DATA TIME 12UTC 07.03.2010

NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 12 HOURS

FORECAST POSITION AT T+ 12 : 24.2S 39.7W

VERIFYING TIME POSITION STRENGTH TENDENCY

-------------- -------- -------- --------

00UTC 08.03.2010 24.2S 39.7W WEAK

12UTC 08.03.2010 27.3S 42.5W WEAK INTENSIFYING SLIGHTLY

00UTC 09.03.2010 29.4S 45.2W WEAK WEAKENING SLIGHTLY

12UTC 09.03.2010 30.1S 47.6W WEAK INTENSIFYING SLIGHTLY

00UTC 10.03.2010 30.1S 47.7W MODERATE LITTLE CHANGE

12UTC 10.03.2010 30.6S 47.7W WEAK LITTLE CHANGE

00UTC 11.03.2010 31.4S 47.0W WEAK WEAKENING SLIGHTLY

12UTC 11.03.2010 32.1S 45.4W WEAK WEAKENING SLIGHTLY

00UTC 12.03.2010 33.5S 42.6W WEAK WEAKENING SLIGHTLY

12UTC 12.03.2010 35.4S 38.2W WEAK LITTLE CHANGE

00UTC 13.03.2010 BELOW TROPICAL STORM STRENGTH

THIS INFORMATION IS PROVIDED AS GUIDANCE FOR TROPICAL CYCLONE

RSMCS. IT REQUIRES INTERPRETATION BY TROPICAL CYCLONE SPECIALISTS

AND SHOULD NOT BE CONSIDERED AS A FINAL PRODUCT

MET OFFICE, EXETER, UK

[Cookie]

Its been eaten by shear though.

[Somerset Squall]

Indeed, and that's why the rare occuring tropical disturbances in the South Atlantic often don't become tropical cyclones.

[Somerset Squall]

This system is now a tropical cyclone.

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

847 AM EST WED MAR 10 2010

GFS DATA AT FTPPRD.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PROD/

SYNOPSIS (VALID FROM 00Z MAR 10). THE UPPER LEVEL ANALYSIS SHOWS

A CLOSED LOW NEAR 33S 45W EXTENDING A SHORT WAVE TROUGH TO THE

NORTHWEST INTO BRASIL ALONG 20S 50W. THIS FEATURE IS DECOUPLING

FROM A WARM CORE SURFACE LOW OFF THE COAST OF BRASIL...WITH

CLOSED CIRCULATION ESTIMATED NEAR 29.6S 48.2W. ALTHOUGH A

TIGHT/COMPACT STORM...IT IS NOW CLASSIFIED AS A TROPICAL CYCLONE

RATHER THAN SUBTROPICAL.