No Mirinae Miracle. Typhoon Mirinae is coming to the Philippines

For the latest info on Typhoon Mirinae (Satni), see Manilla may be spared the worst despite a direct impact from category two Typhoon Mirinae.

Yesterday, a commentor, Jon, posted his thoughts that the Philippine government and media seem to be downplaying the significance of Mirinae.  After all, just last week we were looking at a somewhat miraculous turn by Typhoon Lupit at the last second.

Make no mistake: there will be no last-second turn of Mirinae.

Typhoon Mirinae is caught in the flow of a ridge to the north.  That ridge is expected to remain in place over the next five days.  There is nothing on the maps that will break that ridge down within the next 36 hours.

Quick Hits:

• maximum sustained winds are 90kts (104mph or 167kph), gusts to 110kts (127mph or 204kph), moving west-southwest (260°) at 16kts (18mph or 30kph);
• Mirinae has turned west-southwest in response to the ridge strengthening slightly.  However, this should only continue the next 24 hours before Mirinae resumes a westward track;
• the Joint Typhoon Warning Center forecasts Mirinae to come ashore late Friday night, UTC; maximum sustained winds at that time are forecast at 85kts (98mph or 157kph);
• Mirinae is an elongated cyclone oriented east to west with the center of the system to the far east of the convection; much of the CDO is as cold as to (according to 29/0957Z infrared image from NRL);
• Mirinae still has an established outflow channel to the north per 29/0957Z water vapor imagery; this is due to a tropical upper-tropospheric trough located well east of Mirinae.  However, this connection is likely to get severed soon as the two separate even further;
• Mirinae will continue to exhibit well-established outflow as it is located on the western edge of an upper-level anticyclone; wind shear is rather moderate at 20kts (23mph or 37kph) which will also help to keep the storm from strengthening further;
• based on the 29/0957Z SSMI/S rainfall rate data, Mirinae has three areas of intensive rainfall rates in excess of 1.4 inches/hour.  Based on the 24-hour rainfall forecast totals from eTrap, 29/0600Z, it is possible a slim stretch of the Philippines cutting right through Manilla will see as much as 12 inches of rain.

There are several things that I look at and give significant relevancy to when trying to figure out if a storm will strengthen or not, a few of which are:

1. upper-level divergence -  divergence is, essentially, the splitting of winds which allows updrafts in tropical cyclones.  Mirinae is located beneath an area of great divergence which all other things being equal, would help intensification;
2. oceanic heat potential – oceanic heat potential or OHC is the amount of energy available in the waters.  Currently, Mirinae is over high OHC values of 100-plus kJ cm-2.  As with divergence, all other things being equal, intensification would be most likely;
3. wind shear - there most always will be shear over a cyclone.  The question is: how much?  In Mirinae’s case, we’re looking at 20kts (23mph or 37kph).  This can be a significant neutralizing factor to other favorable conditions.  In  young storms (as we’ve seen in the Atlantic basin), it can be deadly for tropical cyclogenesis – the development of a tropical cyclone in the upper atmosphere.

I won’t lie; I’m actually quite surprised that Mirinae is elongated east/west as it is with the deepest convection to the west.  This is typically the result of easterly wind shear – but I’m not seeing it on the maps.  Maybe I’m just too tired to recognize something.

Nonetheless, the wind shear is seriously negating other favorable aspects of intensification.  So, Filipinos should be very thankful for such.

Am I saying Mirinae won’t strengthen at all?  Of course, not.  I am saying I like the JTWC’s forecast for slight weakening before landfall.

The obvious major area of concern is rainfall.  As mentioned in the last Quick Hit, it’s forecast that, based on Mirinae’s current forward speed and satellite-estimated rainfall rates, some areas can expect as much as 12 inches of rain.

The good news about this is that Mirinae is expected to continue the same forward speed throughout the Philippines.  That will help reduce total rainfall rates.  The bad news is that mountainous regions will create updrafts which will induce higher rainfall rates over certain areas.

Tomorrow, we’ll look in detail at the forecasted rainfall rates and what certain areas of the Philippines can expect to see.

In the meantime, if you live in the Philippines or know of someone who does, please do not take the situation lightly.  While I wouldn’t say that Mirinae will drop as much rain as that of Typhoon Ketsana in September, I will say that the flooding could be very similar.  Grounds are already saturated.  And it won’t take much to create flash-flooding conditions.