Weather TALK [forecasts, etc]

**chua_riwap** · October 31st, 2009 02:30 PM

Buti naman di nagtagal yanbg si Santi.

Sana naman last na ito. Bugbog na tayo sa kalamidad.......

**Jun aka Pekto** · October 31st, 2009 02:36 PM

It weakened as it crossed over land. There's no energy source over land. That quickened its pace. The center also crossed south of Manila. If it crossed north, there probably would be heavier rain because the southwesterly flow would've brought increased energy from the South China Sea. Look at all that enhanced stuff south of the crosshairs.

**Hanren** · November 1st, 2009 08:05 AM

It seems that another storm is fast developing over the pacific. It has a 'fair' potential to become the next storm
From JTWC:

B. TROPICAL DISTURBANCE SUMMARY:
(1) AN AREA OF CONVECTION HAS PERSISTED NEAR 14.6N 132.3E,
APPROXIMATELY 660 NM EAST OF MANILA, PHILIPPINES. ANIMATED INFRARED IMAGERY SHOWS CONVECTION HAS STARTED TO DEVELOP OVER A LOW LEVEL CIRCULATION CENTER (LLCC).

A 310919Z QUIKSCAT PASS HAD INDICATED A WELL ORGANIZED LLCC WITH UNFLAGGED WINDS BETWEEN 15 TO 20 KNOTS, CONFIRMED BY AN OBSERVATION, NEAR THE LLCC, SHOWING 18 KNOTS WITH A 1008.2 MB SURFACE PRESSURE. CONVECTION HAS ONLY BEEN PERSISTENT OVER THE PAST 12 HOURS, AND HAS BEEN PREDOMINANTLY DURING NIGHTTIME COOLING PHASES. UPPER LEVEL ANALYSIS INDICATES THAT THE LLCC IS SOUTH OF AN UPPER LEVEL SUBTROPICAL RIDGE AXIS, PROVIDING GOOD POLEWARD OUTFLOW, WITH ADDITIONAL ENHANCEMENT BY A MID-LATITUDE JET THAT IS CURRENTLY BEING DEPRESSED SOUTHWARD BY A MID-LATITUDE TROUGH TRACKING EASTWARD OVER NORTHERN CHINA. VERTICAL WIND SHEAR (VWS) IS CURRENTLY AT MODERATE VALUES OF 10 TO 20 KNOTS, WITH SEA SURFACE TEMPERATURES AROUND 28 TO 29 CELSIUS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 KNOTS.

MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. BASED ON INCREASING CONVECTION OVER A WELL DEFINED LLCC, BUT MODERATE LEVELS OF VWS, THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS FAIR.

Here's the latest sateliite imagery from JTWC

**Jun aka Pekto** · November 1st, 2009 09:24 AM

The computer models doesn't really develop that latest system into anything more than a tropical wave. There's no discernible closed circulation indicated at the mid levels over the week. There's too much shearing above.

It could enhance thunderstorm/shower activity along many parts of the eastern Philippines though. It's still prudent to keep an eye on it, seeing how off the computer models can be this far out.

**Jun aka Pekto** · November 1st, 2009 10:06 AM

Also.... Typically, enhancement by a mid-latitude jet is significant if we're talking about mid-latitude Lows such as those that move west to east over Japan. They develop from high up and filter down to the surface.

A tropical Low is the opposite. It develops from the surface up. It needs a bubble of nothing going on at all levels because that allows more heating of the ocean waters where a tropical Low gets its energy from. That calm allows a tropical Low to develop from the surface going up. Any activity above and not associated with that tropical system will "shear off" the top part of the developing system which will keep it weak.

I don't like forecasting for both tropical and mid-latitude systems at the same time because the dynamics for each type is different, waaaaay different. My brain becomes confused because I sometimes mix up the dynamics of each one.

**mazzipino** · November 1st, 2009 01:41 PM

OT: You know what, I have more satisfaction reading this thread than listening to what the PAGASA spokesman has to say in the news. Nice work! :D

**vito corleone** · November 1st, 2009 01:43 PM

Originally Posted by mazzipino

OT: You know what, I have more satisfaction reading this thread than listening to what the PAGASA spokesman has to say in the news. Nice work! :D

ot

i love your signature, bro

**Hanren** · November 1st, 2009 07:18 PM

Originally Posted by Jun aka Pekto

The computer models doesn't really develop that latest system into anything more than a tropical wave. There's no discernible closed circulation indicated at the mid levels over the week. There's too much shearing above.

It could enhance thunderstorm/shower activity along many parts of the eastern Philippines though. It's still prudent to keep an eye on it, seeing how off the computer models can be this far out.

Convection (rain clouds) is still weak. The upper level environment remains favorable though with low to moderate vertical wind shear. It still has a fair (not yet good though) chance of ever developing into a significant
storm.

Let's just hope it dissipates right away.

**Jun aka Pekto** · November 1st, 2009 10:17 PM

Originally Posted by Hanren

Convection (rain clouds) is still weak. The upper level environment remains favorable though with low to moderate vertical wind shear. It still has a fair (not yet good though) chance of ever developing into a significant
storm.

Let's just hope it dissipates right away.

There's also a moderate to strong low-level northeasterly flow expected over the waters near Taiwan induced by high pressure over the mainland. That's going to help moderate low-level temperatures, another factor not favoring development. I'm not sure how good the GFS models are. The PAGASA forecasters know what model(s) work best for them. But, the near term trend is to weaken the system which is what I'm going with.

There's still enough activity to bring enhanced shower and thunderstorm activity over the eastern Philippines and northern Luzon might feel a tad bit cooler with that northeasterly flow. PAGASA got it covered pretty well.

**Hanren** · November 2nd, 2009 08:50 AM

It seems that JTWC has upgraded the status of the low to 'good'. This TCFA (Tropical Cyclone Formation Alert) might still be cancelled or upgraded within the next 24 hours.

WTPN21 PGTW 012200
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
155 NM EITHER SIDE OF A LINE FROM 17.3N 127.2E TO 19.0N 122.0E
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS
IN THE AREA ARE ESTIMATED TO BE 20 TO 25 KNOTS. METSAT IMAGERY AT
012030Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 17.8N
126.3E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 16 KNOTS.

2. REMARKS: AN AREA OF CONVECTION NEAR 17.8N 126.3E, APPROXIMATELY
360 NM EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS PERSISTED OVER THE
PAST 12 HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS DEEP CONVEC-
TION BUILDING OVER AN ORGANIZING LOW LEVEL CIRCULATION CENTER (LLCC).
MODERATE VERTICAL WIND SHEAR (VWS) TO THE NORTH OF THE LLCC HAS BEEN
FUELING THE RECENT INCREASE IN POLEWARD OUTFLOW. A 011215Z ASCAT PASS
SHOWED WINDS ALONG THE NORTHERN PORTION OF THE LLCC WERE BEING
ENHANCED BY NORTHEASTERLY FLOW OUT OF THE EAST CHINA SEA (ECS) AND
WERE BETWEEN 20 AND 25 KNOTS. SEA SURFACE TEMPERATURES ARE CURRENTLY
FAVORABLE FOR DEVELOPMENT BUT ARE DECREASING AS THE LLCC TRACKS TO
THE WEST-NORTHWEST AND WILL LIKELY DROP BELOW 28 CELSIUS WITHIN THE
NEXT 12 TO 24 HOURS.

INCREASING NORTHEASTERLY FLOW WILL LIKELY HELP
TO SPIN THE SYSTEM UP WITHIN THE NEXT 12 TO 24 HOURS AS THE LLCC
MOVES TOWARDS NORTHERN LUZON. THE INTERACTION WITH THE NORTHEASTERLY
COLD SURGE OCCURRING OVER THE ECS WILL MAKE DEVELOPMENT POTENTIAL
QUESTIONABLE IN THE LONG TERM, HOWEVER IN THE SHORT TERM DEVELOPMENT
IS FAVORABLE. BASED ON INCREASING LLCC ORGANIZATION, FAVORABLE UPPER
LEVEL OUTFLOW AND MARGINALLY FAVORABLE SST VALUES, THE POTENTIAL FOR
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE IN THE NEXT 24 HOURS
IS GOOD