Thursday, December 4, 2014

Comparing Forecast Track for Super Typhoon Hagupit (Ruby) to Super Typhoon Haiyan (Yolanda)

Super Typhoon Hagupit (Ruby) has intensified into a category-5 Super Typhoon that is threatening the Eastern Visayas, the portion of the Philippines devastated by Super Typhoon Haiyan (Yolanda) just 13 months ago. This powerful typhoon is producing maximum sustained winds of 175 mph and a minimum central pressure of 905 mb (Masters 2014).

Super Typhoon Hagupit (Yolanda) is packing winds of 175 mph as it approaches the Eastern Visayas region of the Philippines. Image: NOAA

Hagupit intensified very rapidly, as the minimum central pressure dropped 49 mb, from 956 to 907 mb, in a 24-hour period, according to personal communication with Brian McNoldy, at the University of Miami. Brian indicated that the error bars on this estimate are large, because recon flights are not taken into tropical cyclones in this region.

Although some early model runs forecast Hagupit (Ruby) to approach the Philippines, but then curve towards the northwest, missing the Island of Samar, recent runs from most models are following the European model, which has been predicting a more westward track. For example, the Joint Typhoon Warning Center's (JTWC) track has now shifted to the southwest. As of yesterday morning in the Philippines, PAGASA was sticking with a more westward track, which it has changed little this evening.

We may wonder how forecast tracks from organizations like PAGASA and the JTWC differ from each other, and differ from the track of Super Typhoon Haiyan last year. I have made a simple graphic showing the difference in these tracks.

Comparing Hagupit (Ruby) forecast tracks from PAGASA and the JTWC with the historic track from Haiyan (Yolanda) last year. Data: JTWC, PAGASA, Unisys Corporation (Haiyan). Image: Hal Needham

Both forecast tracks suggest that Hagupit (Ruby) will move towards the west-northwest and approach the Island of Samar. The JTWC forecasts faster motion, and an earlier arrival than PAGASA. Both of these tracks are currently north of Haiyan's path last year, however, it is imperative not to focus too closely on the exact forecast track, but to leave some north-south margin for error. Therefore, all people from Southern Leyte and Cebu, north through the Visayas to Southern Luzon should closely monitor this dangerous super typhoon.

In fact, it's not out of the question that Hagupit (Ruby) could take a more west-southwest track near Tacloban. The European Model is predicting landfall on Leyte, near Tacloban, around 0200 local time on Sunday morning (Masters 2014). Note the position of Tacloban on this map as a green circle, where Haiyan generated a surge exceeding 6.1 m (20 ft) and killed thousands of people.

Joint Typhoon Warning Center (JTWC) map showing forecast positions and intensity for Super Typhoon Hagupit (Ruby). Readers should include a north-south margin of error and not focus too closely on exact track. Data: JTWC, Image: Hal Needham



I will be updating this blog frequently in the next few days, with perspective on potential storm surge patterns and historical storm surge information for this region.


REFERENCES:
Masters, 2014: Cat 5 Super Typhoon Hagupit Poised to Hit Philippines Islands Devastated by Haiyan. Post12/4/14. Available on the Web at: http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2872.



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