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Public advisoryEdit

TYPHOON CHAN-HOM PUBLIC ADVISORY NUMBER 30

WIKI-HURRICANES FORECASTING CENTER

06:00 PM JST TUE JUL 07 2015

...CHAN-HOM STEADILY DEEPENING...

SUMMARY OF 06:00 PM JST...09:00 UTC...INFORMATION

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LOCATION...18.4N, 136.0E

CENTER POSITION CONFIDENCE: AVERAGE

ABOUT 790 MI...1275 KM SE OF KUNIGAMI, JAPAN

MAXIMUM SUSTAINED WINDS...80 KT...90 MPH...145 KM/H

MINIMUM BAROMETRIC PRESSURE...964 MB...29.45 INCHES

PRESENT MOVEMENT...W AT 11 KT...12 MPH...20 KM/H

DISCUSSION AND 48-HOUR OUTLOOK

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At 06:00 pm JST, the center of Typhoon Chan-Hom was situated near 18.4N, 136.8E, or about 790 miles (1,275 kilometers) southeast of Kunigami, Japan. Maximum sustained winds were 80 knots (90 mph, 145 km/h), with higher gusts. The minimum barometric pressure was 964 millibars (hPa; 29.45 inHg), and the cyclone was tracking west-northwestward at 11 knots (12 mph, 20 km/h). Conditions are expected to remain favorable for Chan-hom to continue strengthening steadily over the next two days as the typhoon tracks without much inhibition towards the southern Ryukyu Islands.

NEXT ADVISORY

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Next complete advisory at 12:00 pm JST.

$$

Forecaster YE

DiscussionEdit

TYPHOON CHAN-HOM DISCUSSION NUMBER 30

WIKI-HURRICANES FORECASTING CENTER

06:00 PM JST TUE JUL 07 2015

Chan-hom has not become much better organized over the past few hours. While the eye is at OW status, the cloud tops are only LG in some places, and the CDO has not smoothed out. While visible imagery shows a formidable hurricane, IR channels suggest otherwise and still show a somewhat ragged appearance. With that said, Chan-Hom features awesome outflow channels. Furthermore, a 5z AMSU pass showed a closed eyewall (unlike a 2224z one), which it did not show for Nangka.

Intensity estimates from SAB, WHFC, and JTWC has not changed throughout the day and remain in excellent agreement at a T4.5.77 knts based on a cured band, CDO, and eye pattern. AMSU and SATCON estimates range from 86-92 knots. In additional, CI values from CIMSS, JMA, and JTWC ADT are at 5.5/102 knts, 5.3/99 knts, 5.5/102 knts respectively, a small increase from a few hours ago due to the fact the 3 hour averages hae caught up with the eye scene type. Under the assumption that Chan-hom could have been stronger earlier, the intensity is set conservatively at 80 knots.

The future track for Chan-hom continues to be fairly straightforward as the number of potential variables that could alter the forecast are has been decreasing. Models are in general agreement that for the next three days, Chan-hom will largely be driven towards the west-northwest to northwest with the subtropical ridge rebuilding towards the west, which puts the southernmost Ryukyu Islands at risk. After three days, forecast models diverge into two potential scenarios. One scenario suggests that Chan-hom will continue bee-lining towards the Chinese mainland once the storm moves into the East China Sea, a scenario which the ECMWF and GFS are in agreement on. The other scenario suggests that a trough will cause Chan-hom to recurve towards the north and eventually northeast, which would cause Chan-hom to either scrape the Chinese coast or avoid the mainland altogether. This is supported by the less reliable CMC and HWRF. Currently the WHFC track forecast suggests that Chan-hom will be moving at a brisk enough pace to get to the Chinese mainland before the trough is able to whisk Chan-hom away from land, and thus favors the reliable ECMWF/GFS models.

Chan-hom is still solidifying its inner core and CDO and should take yet another 12 hours to do so. Thereafter, what little shear there is forecast to relax to near zero, and with it's terrific outflow channels, rapid intensification will likely being. The new forecast is quite aggressive, calling for 50 knot RI from hour 12-36 hours. After day 2, while conditions remain favorable, inner core dynamics such as eyewall replacement cycles could cause for slight weakening. Since we do nkt know what naturally causes ERC's, and the fact that ERC's are hard to predict, I will not commit to a forecasting an ERC and subsequent re-intensification, but rather forecast a slow weakening trend. As you could imagine, weakening is excepted after landfall.

Interests in Taiwan, mainland China, and the Ryukyu Islands of Japan should be monitoring the progress of this typhoon very closely as it has the potential to become a life-threatening tropical cyclone capable of widespread destruction.


INIT 07/0900Z 18.4N 136.0E 80 KT 90 MPH

12H 07/1800Z 18.9N 135.0E 85 KT 100 MPH

4H 08/0600Z 20.6N 133.7E 110 KT 125 MPH

36H 08/1800Z 21.4N 131.9E 135 KT 155 MPH

48H 09/0600Z 23.5N 128.6E 140 KT 160 MPH ... APPROACHING SOUTHERN RYUKYU ISLANDS

72H 10/0600Z 25.4N 124.1E 130 KT 150 MPH ... NEAR SOUTHERN RYUKYU ISLANDS

96H 11/0600Z 28.3N 120.3E 75 KT 85 MPH ... INLAND CHINA

120H 12/0600Z 30.7N 117.6E 15 KT 15 MPH ... INLAND CHINA

$$

Forecaster YE

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