Tropical Storm 18W

[Somerset Squall]

Tropical Depression 18W has formed out to sea in the eastern half of the West Pacific basin. Convection has persisted over a well defined LLC, but now has been sheared to the west. Intensity is 30kts, and moderate shear will cap any major intensity gains in the next 24hrs. Eventually, shear will ease which will promote more rapid development. 18W will move northwestwards along the southwestern periphery of a subtropical ridge anchored to the northeast. This motion will keep 18W over warm waters, thus, 18W is expected to intensify and perhaps become a typhoon in the next few days. It is unclear if 18W will affect land as the depression is currently a long way out to sea.

[Cookie]

Special Statement from NWS GUAM

000

WWMY80 PGUM 262301

SPSMY

SPECIAL WEATHER STATEMENT

NATIONAL WEATHER SERVICE TIYAN GU

901 AM CHST SUN SEP 27 2009

GUZ001>004-PMZ151>154-271100-

GUAM-ROTA-TINIAN-SAIPAN-MARIANAS COASTAL WATERS-

901 AM CHST SUN SEP 27 2009

...TROPICAL DISTURBANCE DEVELOPING NORTH OF POHNPEI...

A DEVELOPING TROPICAL DISTURBANCE IS CURRENTLY LOCATED NORTH OF

POHNPEI ABOUT 900 MILES EAST-SOUTHEAST OF GUAM AND SAIPAN. THIS

INTENSIFYING SYSTEM IS CURRENTLY THE SUBJECT OF A TROPICAL CYCLONE

FORMATION ALERT AND COULD BECOME A TROPICAL DEPRESSION DURING THE

NEXT 12 TO 24 HOURS.

THIS TROPICAL DISTURBANCE HAS BEEN MOVING WESTWARD AROUND 10 MPH

DURING THE PAST DAY OR SO. CONTINUED MOVEMENT AT THIS SPEED WOULD

BRING THIS SYSTEM TO THE VICINITY OF THE MARIANA ISLANDS ON

WEDNESDAY. HOWEVER...FOR SYSTEMS THIS FAR AWAY...CONSIDERABLE

UNCERTAINTY EXISTS CONCERNING THE EXACT TRACK OF THE SYSTEM...AS

SMALL CHANGES IN COURSE AND SPEED CAN ADD UP TO LARGE DEVIATIONS

OVER TIME. IN ANY EVENT...RESIDENTS OF THE MARIANAS ARE ADVISED TO

CLOSELY MONITOR THE PROGRESS AND EVOLUTION OF THIS DISTURBANCE

DURING THE NEXT COUPLE OF DAYS.

THE SCATTERED SHOWERS THAT ARE FORECAST TO AFFECT GUAM AND ROTA

TODAY (SUNDAY) ARE NOT ASSOCIATED WITH THIS DISTURBANCE...BUT ARE

BEING CAUSED BY A SEPARATE AND WEAKER SYSTEM LOCATED ABOUT 370 MILES

SOUTHEAST OF GUAM AND 385 MILES SOUTHEAST OF ROTA. THIS SYSTEM IS

EXPECTED TO MOVE WEST OF THE MARIANAS BY MONDAY EVENING.

THE NATIONAL WEATHER SERVICE WILL UPDATE THIS STATEMENT AS NEEDED.

$$

MCELROY/GUARD/CHAN

I hope this doesn't effect GAUM to badly

[Cookie]

battling shear

[Somerset Squall]

Indeed Cookie, though this shear has eased a touch and 18W has become a tropical storm overnight, with intensity now at 35kts. However, 18W is not expected to develop much further, and seperation distance from TS 19W (now TS Parma), is expected to decrease, with current forecasts expecting TS18W to be absorbed by Parma in a few days time. 18W is accelerating away from TD20W to the east, but this is bringing the storm closer to Parma, which is the stronger of the two storms. With the fujiwhara interaction and then absorbtion, 18W may not have that much time left to strengthen, and may not as shear could increase from the outflow of Parma.

[Cookie]

A strong chance of fujiwhara interaction then?

I love a good bit of fujiwhara interaction

[Cookie]

htt

[Somerset Squall]

LOL Cookie.

18W is clearly showing the negative effects of being sandwhiched in between two larger storms. Parma and Melor are really stopping 18W from intensifying. JTWC comment that the outflow and inflow of 18W is being severely hampred by the outflow from Parma and Melor. The storm consists of a rather shapeless area of convection over an increasing elongated LLC. The LLC of 18W is likely to become further distorted when it gets closer to Parma, before Parma absorbs 18W in a couple days time.

[Somerset Squall]

With the distinct lack of outflow and increased shear caused by Parma and Melor, 18W has dissipated. It's remnant energy will be absorbed into Parma in the next day or so with no effect to the typhoon.

Edited September 30, 2009 by Somerset Squall

[Cookie]

thanks for the updates on the vanished system.