CIMSS TPARC Support Blog

Textbook example of an anticyclone over TCS025. I’ve posted both a large and storm scale image. The storm scale image has divergence plotted over the AMVS. AMVs and images valid 16Z 29 August, 2008

TCS025 is strenghthening. 18Z is 4am local in Guam, early in the morning. As cloud tops radiate to space, they cool, lowering temperatures aloft more than at the surface. This increases convection. In the IR animation below you can see the convection pick up once again. TCS025 is still fairly elongated, and expected to move off quickly to the northwest, but for now it’s strengthening.

IR Animation showing a diurnal increase in convection.

This small unorganized system has continued to develop. Attached below is the animated IR image with AMVs and analyzed divergence overlayed:

MTSAT-IR image, upper level AMVs and analyzed divergence of TCS025. Valid 13Z 28 August, 2008.

As seen in the animation, TCS025 has decent outflow to it’s north. The convection isn’t organized or symmetric, but it’s fairly wide-spread. It seems to be interacting with a fairly strong upper-level low to it’s north and northwest. This low may be the key to it’s forward motion.

What about surface circulation?

Here is the same IR with a quickscat analysis valid on 07 Z on the 28th of August along with low-level AMVs.

MTSAT-IR image with low-level AMVs and recent quickscatt analysis. Image and AMVs valid 13Z, 28 August, 2008. Quickscat Valid 07Z.

From the image, you can see an almost complete low-level circulation, missing a northerly component on the system’s west side. There is however, one ship report at 20 N, 145E of a fairly weak northwesterly wind.

The water underneath is fairly warm (around 30C). It’s survival is most likely related to the interaction with that trough to it’s northwest.

As nothing is particularly imminent, I’ll do a brief map discussion.

Upper level AMVs and MTSAT IR Image. TCS invests are annotated. Valid 13z 27 Aug, 2008

In this image, you can see the three T-PARC invests and Tropical Depression 14W. TCS025 has been the focus of the experiment for the past few days. It’s currently pretty close to Guam and is predicted to strengthen a bit and potentially threaten Japan over the next few days.

Comparing this analysis with the GFS 12-hour forecast (initialized from the 00 UTC run):

Annotated 12-hour GFS forecast of 850 hPa vorticity and streamlines.

One can see that the GFS forecast has most of the general features. TD 14W is placed fairly well within the model.  TCS027 is analyzed a bit too far south as compared to the satellite image. TCS025 and TCS028 are fairly well represented here in the forecast.

The GFS is continuing to develop this system over the next day or so before sending it off northwestward and weakening it. The GFS also brings the remnants of TD14 up along the China coast and eventually merging with a midlatitude disturbance near Japan. The model has been consistent with the development of TCS025, but not with its future track and landfall. Japan looks like the place to watch over the weekend.

You can see this 00z run of the GFS here.

We’re looking at some clusters of convection, roughly centered on TCS025 right now.

You can see the system in the animation below:

IR image, upper-level AMVs and analyzed divergence. Valid 19z 26 August, 2008.

This system is on the southside of an upper level low with underneath a fairly good region of upper level divergence. In the GFS, this system develops over the next 24 hours or so (12z on the 27th) as seen in this vorticity loop. The system moves up towards Japan and weakens over the next few days according to the model. It will be worth looking at this structure as it develops over the next 24 hours.

Deep-layer wind shear and MTSAT Water Vapor Image. TCS026, located at about 18N 155E is just south of a region of fairly low shear.

If the GFS is correct in it’s motion, the shear analysis shown above has it moving into a region of relatively low shear.

This system is worth keeping an eye on for the next few days.

Here are two animations showing some of our satellite products as they trace Nuri through gensis and beyond.

The first, our upper-level divergence product is shown here (java animation).

The second, our shear product is shown here (java animation).

The divergence product shows Nuri from pre-genesis stages (00z 14 of August, 2008) until 22z 18 August, when Nuri is nearly 80 kts. From just after the onset of the animation, you can see the divergence around Nuri. Although the magnitude varies quite a bit throughout the animation, you can see a fairly coherent signal of 10 - 20 (s-1) over a relatively large region surrounding Nuri. Generally, this divergence is focused to the south of the storm, where most of its outflow was contained. From these animations, it’s difficult to see if the divergence can predict intensification, but it is clearly a sign of a strong sytem.

The shear product is also useful for understanding Nuri, although it does present a bit of a mystery. As you can see Nuri develops under fairly weak shear (5 to 10 kts). But, after Nuri begins to intensify during the 18th of August, you’ll see that Nuri enters a region of relatively very high shear. Keep in mind, however, that this shear is geo-relative: the storm’s motion is not accounted for. As the storm is moving to the west and the shear is from the northwest, some of its impact might be lessened. This is certainly an area for future research.

The 12z run on August 20, 2008 is doing different things with this invest.

The GFS model seen here seems to split up the disturbance. It develops something fairly far to the north at 144 hours, and has a weak disturbance that heads toward the China coast, but it doesn’t seem particularly coherent.

The NOGAPS model seen here pretty much kills off 17C. It also seems to develop a weaker mid-latitude system by the 26th.

The Met Office Model here develops a weak disturbance that heads off toward the Philipeans. Previous model runs have been a bit more aggressive with development so will see what happens.

As of 12z on the 19th of August, Nuri currently has 95 kt sustained winds centered at 18.2 N, 124.4 E.

It’s a fairly sheared system, as you can see from this enhanced IR image with associated AMVs:

Enhanced IR image and associated upper level AMVs for Tyhpoon Nuri. As of 12z Nuri has sustained winds of 95 kts

The forecasted track is shown here:

Enhanced IR image and forecast track for Tyhpoon Nuri.

An 8z AMSU pass shows a reasonable warm core aloft, and gives an intensity of 93kts. The ADTs 14z analysis gives an intensity of 61 kts, while the CIMSS SATCON gives an intensity of 92kts.

The question of this track with regards recurvature. At this time it looks like Nuri will continue it’s slight northwesterly track as it is driven by a strong ridge to its northeast. If this happens, it’s unlikely that any more aircraft flights will be possible as part of TPARC. Attention will probably turn to TCS 17.

JTWC has Nuri intensifying to 105 kts by 12z on the 21st, before making landfall in China at about 12z on the 22nd. The OHC maps have some higher energetic waters around the Philipino coast, perhaps explaning some of their reasoning for intensification despite the fairly high shear environment.

As the West Pacific is fairly quiet, it is worth looking and some smaller features and at least examine connections between the surface and the atmosphere aloft.

Here is an IR image with upper-level AMVs and divergence contoured above it from 13z on 13 August, 2008 of TCS invest 014.

IR image, upper-level AMVs and upper-level divergence for TCS invest 014. The strongest convection and divergence lie on the eastern side of the invest.

The strongest convection, outflow and divergence seem to be to the east. What’s causing this asymmetry? One possibility is to look at the Ocean Heat Content product:

Ocean Heat Content for TCS invest 014, valid 12Z 2008, August 13th. As seen in the image, the ocean surface may be fueling this asymmetry.

A more difficult question to answer is whether the divergence is a reaction to the intensification from the ocean surface, or whether the divergence helps intensify the storm. It’s a question that will hopefully be addressed with some research from this experiment.

Here’s a quick animation (click on the image) of 98W over the Philippines. You can see some outflow from the AMVs to its northeast.

You can also see some of the trade wind flow to its south.

This storm is being monitored for development over the next few days.