Typhoon Mirinae Forecast Track Points to Luzon, Philippines Landfall at end of week October 29, 2009

Typhoon Mirinae Appears Certain to Strike the Philippines

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Typhoon Mirinae Forecast Track click for most recent map

The Typhoon Mirinae Forecast Track remains generally unchanged as does the intensity.  It continues to move west at a pretty good clip and that may end up being a good thing for the Philippines.   The JTWC forecast track has been nudged a tad farther south than previous runs which would send the typhoon across the island closer to Manila.  While Luzon really can’t handle a lot of rain, it’s going to get it as well as winds along the coast perhaps as high as 105 to 110 mph or 95 kts with higher gusts.  With the forward momentum of Mirinae, I suspect that whatever the maximum storm surge in that area with this type of storm will be likely.  The biggest difference between the NOGAPS and GFS models is the timing.  Over 117,000 Filipinos remain in shelters as a result of Typhoon Parma and Tropical Storm Ketsana.  So, the government of the Philippines is warning the potential for  landslides and flooding.  The government is particularly concerned because All Saints Day, November 1, is traditionally a day when Filipinos visit cemeteries to remember ancestors.

Typhoon Mirinae Satellite Loop Click for most recent loop

The NOGAPS advertises a typhoon moving at a pretty good pace with a landfall outlined just prior to 12Z on Friday October 30.  It also favors a landfalling tropical cyclone with a central pressure a shade less than 996 mb.  The GFS on the other hand doesn’t come up with as robust a system as the NOGAPS.  The central pressure at landfall is something between 996 mb and 100 mb.  If that is verified, I find it hard to determine how a storm with that level of pressure could support the JTWC contention that a 95 kt typhoon will strike the Philippines.  My experience tells me that pressures that high generally does not support winds of 95 kts unless it was a major tropical cyclone that was winding down and even that is not evidence of support.  Falling winds mean that the pressure cannot support that wind level.    Other than that, the GFS is much slower than the NOGAPS with a landfall with a landfall not coming until just after 00Z on Saturday Oct 31.  That is a big difference because if Mirinae moves that slowly then it would be dropping heavy rain on the Philippines for many hours longer than the NOGAPS solution. 

Typhoon Mirinae Water Vapor Loop click for most recent loop

The typhoon has been moving at a steady speed and so unless something shows up to slow its forward speed then it seems reasonable that the JTWC forecast of having the core of the storm over Luzon for less than 24 hours is very plausible.  On the other hand, that also means that the fine folks of Manila and other parts of the Philippines will probably experience pretty decent winds….maybe even typhoon force…for the duration of the storm because Mirinae just wouldn’t have time to fall apart…but it will weaken.  This storm got stronger than anticipated due to a trof to the north that was enhancing the outflow to the north.  Interestingly, that trof was actually created from the remnant of Typhoon Lupit which moved northeast offshore of Japan, turned extratropical and created a front trailing off from it.  With that feature moving out,  there isn’t any real mechanism that would help enhance the intensity substantially.  The only thing that will help it get stronger is an increasing outflow aloft, but that will be offset somewhat by a little bit of vertical shear.  The JTWC notes that the shear has already messed up the visibility of the eye. 

Watch 72hr loop of Total Precipitable Water Showing development of Typhoon Mirinae

If one assumes a rapid movement across the Philippines, then one might assume that the storm will not deteriorate that much over land and will emerge in the South China Sea in good shape.  So good that it may redevelop.  But, sea surface temperatures in the central South China Sea have dropped off a bit due to a recent shot of unseasonably cold air in the area.  So, the JTWC forecast reflects that situation by reducing the intensity of the storm as it approaches Vietnam.  Mirinae may fall to tropical storm status before landfall.  However, Vietnam also suffered from Typhoon Ketsana and Typhoon Parma, though Parma was closer to Hanoi.  In any event, the ground in Vietnam is pretty saturated so if they get a tropical storm instead of a typhoon, it is really immaterial as the forward motion will be the key for Vietnam.  Vietnam suffered over 3/4 of a billion US dollars just from Ketsana.   If the storm slows down once it’s inland over SE Asia, then excessive rainfall can be anticipated.  The thing that everyone wants is for the storm to keep moving. 

WDPN32 PGTW 290300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (MIRINAE) WARNING NR 13//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TYPHOON (TY) 23W (MIRINAE) HAS INTENSIFIED TO 90 KNOTS AND
MAINTAINED A WESTWARD TRACK UNDER THE INFLUENCE OF THE SUBTROPICAL
STEERING RIDGE OVER THE PAST 12 HOURS. RECENT ANIMATED MULTISPECTRAL
IMAGERY SHOWS EVIDENCE OF EASTERLY VERTICAL WIND SHEAR THAT HAS
CAUSED MIRINAE TO LOSE ITS EYE-LIKE FEATURE OVER THE LAST 12 HOURS.
HOWEVER, THE SYSTEM STILL HAS GOOD POLEWARD OUTFLOW INTO THE MID-
LATITUDE WESTERLIES AS WELL AS ACCESS TO POLEWARD OUTFLOW INTO THE
TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) LOCATED APPROXIMATELY 15
TO 20 DEGREES EAST OF THE SYSTEM. THE CURRENT POSITION IS BASED WITH
HIGH CONDIFENCE ON POSITION FIXES BY RJTD AND PGTW AND IS SUPPORTED
BY A 282127Z SSMI MICROWAVE IMAGE. THE CURRENT INTENSITY IS BASED ON
DVORAK ESTIMATES OF 90 KNOTS FROM PGTW AND RJTD.
3. FORECAST REASONING.
    A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
    B. THE TYPHOON WILL CONTINUE TO TRACK WESTWARD THROUGH THE
FORECAST PERIOD AND WILL RETAIN RADIAL OUTFLOW, ENABLING EXHAUST
INTO THE MID-LATITUDES, AS IT TRACKS SOUTH OF A NARROW SUBTROPICAL
RIDGE. FURTHER INTENSIFICATION IS EXPECTED TO BE LIMITED, MAINLY DUE
TO THE LACK OF A STRONG (POLEWARD) OUTFLOW CHANNEL AS THE SYSTEM
TRACKS FURTHER AWAY FROM THE TUTT MENTIONED IN PARA 2.A. MIRINAE IS
EXPECTED TO MAKE LANDFALL IN THE PHILIPPINES AND WEAKEN JUST BEFORE
TAU 48.
C. BEFORE TAU 72 THE SYSTEM WILL EXIT LUZON INTO THE SOUTH CHINA SEA
AS A MUCH-WEAKENED TYPHOON. A COOLER POOL OF SEA SURFACE TEMP-
ERATURES IN THE CENTRAL SOUTH CHINA SEA, MINIMAL OCEAN HEAT CONTENT
VALUES AND DIMINISHED POLEWARD EXHAUST WILL PROMOTE STEADY
WEAKENING. AN EARLY SEASON COLD SURGE WILL ALSO AID IN WEAKENING THE
SYSTEM CLOSER TO TAU 96. THE MODEL GUIDANCE IS IN STRONG AGREEMENT
WITH THIS FORECAST SCENARIO. THEY ALSO SHOW A GROWING TREND TOWARDS
A MORE SOUTHWESTERN TRACK IN THE EXTENDED TAUS.//

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Typhoon Mirinae Forecast Track Toward Flood Plagued, Disease Infested Portion of Philippines October 28, 2009

Typhoon Mirinae IR Color Satellite-Click image for most recent loop

Get most recent update on Typhoon Mirinae forecast track and latest on potential for volcano eruption as Mirinae strikes the Philippines, CLICK HERE

Watch 72hr loop of Total Precipitable Water Showing development of Typhoon Mirinae

Typhoon Mirinae was born from the developing Tropical Storm 23W, as expected.  The storm has been moving along at a pretty good clip. So far it has tended to move faster than the general forecast.  I suspect that is why the Joint Typhoon Warning Center has gone along with the early forecast landing in the Philippines at around 12Z October 30 that is brought out by the NOGAPS model.  The GFS is remarkably similar to the NOGAPS in the track and intensity with both advertising a tropical cyclone with a central pressure somewhere between 992 and 1000 mb near the same location in the Luzon province that Typhoon Parma struck.  But, the GFS wants to take the storm into the Philippines somewhere between 12z and 18z October 31.  Given the persistent forward speed and little evidence that there is much out there to slow this guy down, the early forecast landfall is probably a fair bet. 

Typhoon Mirinae Forecast Track Updates Regularly-Click on Image

Tropical Storm 23W not only has been moving faster than forecast, it also has developed faster than forecast.  It was not anticipated by the JTWC to become Typhoon Mirinae until 12Z October 28 but had done so by 18Z October 27.  That is not overly significant except that it is obviously in a upswing mode.   The risk here is that with the storm’s forward speed and the fact that its in an intensication process, odds are pretty high that the Philippines will be struck by a tropical cyclone that is intensifying, not weakening.  One thing that has been right on the money is the forecast track.  Typhoon Mirinae moved northwest south of Saipan near Andersen Air Force base  while it was still Tropical Storm 23W.  As anticipated,  the storm went a few hundred more miles on that course and now has taken a more westerly track.  The good news is that the forward speed that it is showing and that is forecast will mean that it would cross the Philippines in less than 24 hours.  That would tend to cut down on excessive rain, though very heavy rain in a short period of time can be expected. 

Typhoon Mirinae Vis Sat w/low level wind barbs 23:13Z 10.27.09

The  bad news is that Luzon cannot handle much in the way of heavy rain.  The storm flow will be slamming into the same mountainous regions that experienced mudslides from Typhoon Parma and Tropical Storm Ketsana and those mountains will do nothing but enhance the rainfall rates.  If the forecast holds and verifies, then Typhoon Mirinae will hit in almost the exact same spot at Typhoon Parma and will track due west near Manila, similar to Tropical Storm Ketsana.  Also, the forward momentum and expected maximum winds of 100 kts would create a pretty good storm surge to the right of the center of the landfall, which is something that did not occur with either Typhoon Parma or Tropical Storm Ketsana.  The flood ravaged Philippines is no where close to recovering from Parma and Ketsana as disease has now broken out in Luzon.  The World Health Organization is helping to try and control an outbreak of  leptospirosis and if Mirinae does as expected, the situation will do nothing but get worse.

Typhoon Mirinae Water Vapor Loop-click image for most recent loop

There is one more bit of bad news that could prove to be the biggest factor in the saga of the Philippines.  When I looked beyond the landfall time of Typhoon Mirinae, I noticed that the typhoon moves across the South China Sea into Vietnam, which means the exact same areas that got hit by Ketsana in both the Philippines and Vietnam will get nailed again and some of the areas affected in Vietnam by Parma will also get heavy rains and wind from Mirinae.  But, maybe more importantly I noticed another tropical cyclone right on the heels of Typhoon Mirinae.  It is not that well developed at only about 1008 mb.  But, both the NOGAPS and the GFS show this feature and it is forecast to track right into Luzon.  Often, a weak tropical cyclone can bring extremely heavy rains.  Since they are not well developed, they don’t necessarily follow typical steering trends and often times will slow down and fall apart over one area, dropping a lot of rain.  This scenario is many days away if it were to occur, but it is showing up on at least two models. So, its’ worth noting.

WDPN32 PGTW 280300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 23W (MIRINAE) WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. TYPHOON (TY) 23W (MIRINAE) IS TRACKING WESTWARD OVER THE PAST
12 HOURS AND HAS RAPIDLY INTENSIFIED TO 75 KNOTS. DVORAK ESTIMATES
FROM PGTW, KNES AND RJTD CURRENTLY SUPPORT INTENSITIES FROM 75 TO 90
KNOTS. THIS FORECAST IS PRIMARILY BASED ON THE PGTW AND RJTD
ESTIMATES. MICROWAVE IMAGERY OVER THE PAST 12 HOURS HAS SHOWN A WELL
DEFINED EYE HAS DEVELOPED, AND IS BEGINNING TO BE APPARENT IN
MULTISPECTRAL IMAGERY AS WELL. THE POLEWARD OUTFLOW CHANNEL HAS
REMAINED WELL ESTABLISHED OVER THE PAST 12 HOURS WITH THE MID-
LATITUDE TROUGH NORTH OF TY 23W THAT HAS STARTED TO LIFT OUT TO THE
NORTHEAST. STRONG ZONAL FLOW ACROSS SOUTHERN JAPAN IN THE UPPER
LEVEL HAS STARTED TO REPLACE THE TROUGH AS THE PRIMARY MECHANISM FOR
POLEWARD OUTFLOW. THE COMBINATION OF THE TROUGH AND DEVELOPING ZONAL
FLOW HAS SUPPORTED THE RECENT INTENSITY CHANGE OBSERVED. RADIAL
OUTFLOW, ASSOCIATED WITH AN UPPER LEVEL POINT SOURCE ANTI-CYCLONE
LOCATED TO THE EAST OF TY 23W, HAS MAINTAINED AN EQUATORWARD OUTFLOW
CHANNEL OVER THE PAST 12 HOURS.
3. FORECAST REASONING
    A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
    B. TY 23W WILL MAINTAIN A GENERAL WESTWARD TRACK TOWARDS LUZON
THROUGH TAU 72 UNDER THE INFLUENCE OF A WELL ESTABLISHED MID-LEVEL
SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH OF MIRINAE. OUTFLOW
FROM THE MID-LATITUDE TROUGH AND ZONAL FLOW WILL DIMINISH SLIGHTLY
OVER THE NEXT 24 HOURS, BUT CONTINUED RADIAL OUTFLOW WILL ALLOW FOR
STEADY INTENSIFICATION THROUGH TAU 72. THE INTENSIFICATION WILL BE
SUPPORTED BY LOW VERTICAL WIND SHEAR CONDITIONS PERSISTING THROUGH
THE ENTIRE FORECAST, ALONG WITH FAVORABLE SEA SURFACE TEMPERATURES
AND OCEAN HEAT CONTENT.
    C. BEYOND TAU 72 MIRINAE IS EXPECTED TO MAKE LANDFALL WITH
LUZON, WEAKEN AND SLOW SLIGHTLY DUE TO THE LAND INTERACTION, THEN
CROSS INTO THE SOUTH CHINA SEA AROUND TAU 96. AS THE SYSTEM RE-
CONSOLIDATES THE INTENSITY IS EXPECTED TO REMAIN STEADY THROUGH TAU
120. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH THE FOLLOWING
FORECAST, EXCEPT WITH THE SPEED OF ADVANCE OVER LUZON. MODELS
SUGGEST LITTLE TO NO SLOW-DOWN AS TY 23W CROSSES OVER LUZON. THE
FORECAST INCORPORATES A DECREASE IN TRACK SPEED FROM TAU 72 THROUGH
120 BASED ON LAND INTERACTION WITH THE LOW LEVEL CIRCULATION.//
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