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Somerset Squall

Tropical Storm Marty

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Invest 97E has now been classed as a tropical depression. Convection has been deep and persistant for 12hrs now over the LLC. The LLC is not all that well defined at the moment and appears to be elongated southwest/northeast. However, with low shear and warm waters for the next 24hrs, 16E has the potential to organise into a tropical storm. After this, waters cool significantly, which will cause rapid weakening and degeneration into a remant low, possibly within 3 days.

16E shouldn't effect land as it slides away to the southwest of Baja California.

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16E's convectional coverage has expanded over the last few hours, and the LLC, though still a little elongated, has consolidated further. Therefore, the depression has been upgraded to Tropical Storm Marty, with intensity now at 35kts.

Marty still has another 24hrs to strengthen, before waters cool and shear increases. NHC are predicting a peak of 45kts, which I agree with. There has been a fair few storms in this basin which have rapidly strengthened, but this appears unlikely in this case as the circulation is not tightly wound at present.

post-1820-12531142005856_thumb.jpg

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Marty still doesn't look all that impressive this evening, and intensity has modestly increased to 40kts. Moderate southeasterly shear is impinging on the system, and will become high beyond 24hrs. Thus, Marty doesn't have that long to intensify. It's possible Marty could well have already peaked if the current shear manages to disrupt the convection coverage over the LLC. Marty lacks convectional banding which suggests this isn't a storm that is going to strengthen much further.

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ep200916.gif

000

WTPZ31 KNHC 162037

TCPEP1

BULLETIN

TROPICAL STORM MARTY ADVISORY NUMBER 3

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP162009

200 PM PDT WED SEP 16 2009

...MARTY A LITTLE STRONGER...

AT 200 PM PDT...2100 UTC...THE CENTER OF TROPICAL STORM MARTY WAS

LOCATED NEAR LATITUDE 18.9 NORTH...LONGITUDE 112.6 WEST OR ABOUT 325

MILES...525 KM...SOUTH-SOUTHWEST OF THE SOUTHERN TIP OF BAJA

CALIFORNIA.

MARTY IS NEARLY STATIONARY. A SLOW NORTH-NORTHWESTWARD MOTION IS

EXPECTED TO BEGIN LATER TODAY....AND MARTY IS FORECAST TO MOVE

NORTH-NORTHWESTWARD THURSDAY AND THURSDAY NIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/HR...WITH HIGHER

GUSTS. SOME SLIGHT STRENGTHENING IS FORECAST DURING THE NEXT 24

HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 70 MILES...110 KM

FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB...29.56 INCHES.

...SUMMARY OF 200 PM PDT INFORMATION...

LOCATION...18.9N 112.6W

MAXIMUM SUSTAINED WINDS...45 MPH

PRESENT MOVEMENT...STATIONARY

MINIMUM CENTRAL PRESSURE...1001 MB

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT

800 PM PDT.

$$

FORECASTER BROWN

000

WTPZ41 KNHC 162040

TCDEP1

TROPICAL STORM MARTY DISCUSSION NUMBER 3

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP162009

200 PM PDT WED SEP 16 2009

VISIBLE SATELLITE IMAGERY INDICATES THAT MARTY HAS MOVED VERY LITTLE

SINCE THIS MORNING. THE CLOUD PATTERN IS THAT OF A VERY ASYMMETRIC

TROPICAL CYCLONE...WITH ALL OF THE DEEP CONVECTION OVER THE WESTERN

SEMICIRCLE OF THE STORM. DVORAK T-NUMBERS OF 2.5 AND 3.0 SUPPORT

INCREASING THE INITIAL INTENSITY TO 40 KT. A SHEAR ANALYSIS FROM

UW-CIMSS SHOWS ABOUT 15 KT OF SOUTHEASTERLY SHEAR OVER THE CYCLONE.

THE SHEAR IS FORECAST TO BECOME SOUTHERLY...THEN TURN SOUTHWESTERLY

IN ABOUT 24 HOURS. IT APPEARS THAT THERE IS SMALL WINDOW OF

OPPORTUNITY FOR MARTY TO STRENGTHEN DURING THE NEXT DAY...

THEREAFTER INCREASING SHEAR AND A LESS FAVORABLE THERMODYNAMIC

ENVIRONMENT SHOULD INDUCE A MORE RAPID RATE OF WEAKENING. THE

OFFICIAL INTENSITY FORECAST IS CLOSEST TO THE STATISTICAL GUIDANCE

FOR THE FIRST 24 HOURS...THEN IS IN GOOD AGREEMENT WITH THE

INTENSITY CONSENSUS THEREAFTER.

MARTY IS EXPECTED TO BEGIN MOVING SLOWLY NORTH-NORTHWESTWARD SOON

AS A WEAK RIDGE BUILDS TO THE EAST OF THE CYCLONE. THE NEW

FORECAST IS CLOSE TO THE PREVIOUS ADVISORY AND NEAR THE MIDDLE OF

THE GUIDANCE ENVELOPE DURING THE FIRST 48 HOURS. THEREAFTER...A

SIGNIFICANT WESTWARD SHIFT HAS BEEN MADE TO THE NHC TRACK...AS

NEARLY ALL OF THE DYNAMICAL MODELS TURN MARTY WESTWARD IN THE

LOW-LEVEL FLOW AS IT WEAKENS AND BECOME A SHALLOW SYSTEM.

FORECAST POSITIONS AND MAX WINDS

INITIAL 16/2100Z 18.9N 112.6W 40 KT

12HR VT 17/0600Z 19.2N 112.7W 45 KT

24HR VT 17/1800Z 19.7N 113.0W 50 KT

36HR VT 18/0600Z 20.4N 113.4W 45 KT

48HR VT 18/1800Z 21.2N 113.9W 35 KT

72HR VT 19/1800Z 22.6N 115.3W 30 KT...REMNANT LOW

96HR VT 20/1800Z 23.5N 117.0W 25 KT...REMNANT LOW

120HR VT 21/1800Z 23.5N 120.0W 20 KT...REMNANT LOW

$$

FORECASTER BROWN

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Marty did not strengthen beyond 40kts. Intensity has been reduced to 35kts, and Marty is taking on a lot of dry air now, which is surpressing persistant convection. Marty is now veering westwards as the shallower system is being steered by low level flow. This means Marty will not be a threat to land. Dry air and then increasing shear should dissipate Marty in a day or two.

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The LLC of Marty has been devoid of convection for a good 18 hours now, thus he is declared a remnant low. The combination of dry air, high shear and cool sea temps should prevent re-development. The remnant low will head westwards into open waters, steering by the low level flow. The circulation will spin down in a couple days.

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