Sinlaku: 13Z, September 18th, 2008
Sinlaku is still churning away. It was briefly upgraded to a Typhoon at 00Z on the 18th, then downgraded back to a Tropical Cyclone. According to JTWC, as of 12Z on the 18th, it was located near 31.0N 131.5E, moving 060 degrees at 09 kts. They analyze it at 55 kts with gusts to 70 kts.
Attached below is the standard IR/AMV/divergence plot valid 13Z on September 18th:
Although Sinlaku has continued outflow to the northeast, it’s flow is very well contained on the west side as it gets caught up in the midlatitude westerlies. The shear over Sinlaku, shown below, is very strong from the west:
The satcon analysis below shows Sinlaku’s recent intensity trend:
You can see the brief peak in intensity from JTWC (black curve) and the slight upward trend from SATCON and the ADT. Reading their prognostic reasoning, it appears JTWC re-intensified the storm based on recon data from TPARC.
Sinlaku may have re-intensified partially because its center has remained over water. This may allow it to maintain its tropical characteristics a bit longer than if it had passed over land.
As it begins ET, we will focus a bit on the tilt of its vortex. Currently, its low level center is a bit displaced to the southwest from the maximum convection as seen in the attached 85 GhZ and divergence plot:
The displacement isn’t huge, but the center (shown by the hurricane symbol, and the slightly circular pattern in the microwave image) is slightly over from the more intense microwave images and the divergence maximum. As ET happens, we’d expect more a vortex title. We’ll explore other ways to show this.
In the short term, the models are fairly consistent in bringing Sinlaku just south of the Japanese islands. There are some slight differences in terms of time and storm size, but the broad picture is fairly similar.
After Sinlaku leaves Japan, the models take a few different tacks with it’s track. The Met Office model and NOGAPS both bring Sinlaku up fairly far north and intensifying it, threathening the Aleutian Islands.
The ECMWF model merges Sinlaku with another midlatitude system, eventually moving toward Alaska.
The GFS takes a middle path: bringing Sinlaku up the Aleutians, but at a slower pace, and with less intensity than the Met Office.
It’s quite easy to see how uncertainties at this stage of forecasting can easily affect long-range forecasting downstream on the US coast.
And the phase diagrams? The GFS diagram begins to develop an assymetric core by the 19th, but does not really become cold core until the 24th of September!
The NOGAPS is faster: generating the assymetric core right away with Sinlaku becoming cold core just before the 20th.
The Met Office model diagram keeps it warm core throughout the shown forecast period.
How will Sinlaku interact with the midlatitute jets and outflow? When will it become extratropical? How strong will it get? These are questions that will need further investigation.
Tags: Extra Tropical Transiton, Sinlaku, TCS033, Track