Average 20 year old weather nerd. Plymouth State University Meteorology, Class of 2018. NOAA Hollings scholar. Summer 2016 intern at NWS Boston.
By: MAweatherboy1 , 1:37 AM GMT on April 08, 2014
Good evening. If you have not already done so, I recommend reading over my previous blog entry, which contains my complete seasonal forecast for the 2014 North Atlantic Hurricane Season. Tonight, however, I'm shifting gears to look at a completely different part of the world, the southeast Pacific Ocean. There, Tropical Storm Ita is intensifying tonight. Ita has already left significant devastation in the Solomon Islands, where river flooding from heavy rains from the developing Ita over the past few days have killed at least 16 people, with more missing. Ita is now pulling away from this island nation, and is setting its sights on northeast Australia. As of the latest (5PM EDT) advisory from the Joint Typhoon Warning Center (JTWC), Ita is located about 530 nautical miles northeast of Cairns Australia, and tracking slowly northwestward at about four knots. Its persistent slow speed was the primary reason for such severe flooding in the Solomon Islands as it was developing in that area. Ita's maximum 1 minute sustained winds are estimate at 60kts, or near 70mph, so Ita is just under the minimal threshold for hurricane-equivalent strength.
Figure 1: Tropical Storm Ita
Figure 2: A visible satellite look at Ita. While the overall trend is for organization, the convective pattern is a bit disorganized right now.
Forecast for Ita
It may just be the fact that I haven't written a tropical weather blog on a specific cyclone in ages, but Ita seems to be a particularly interesting storm to forecast, especially in terms of track. The next two days are fairly straightforward for track, with Ita almost certain to continue a westerly turn and then a bit south of west after this with a ridge building in north and northeast of the storm. While it will speed up somewhat compared to what it has been doing, it will remain a fairly slow mover for the next couple days. Things start to get more interesting after this time, as a significant shortwave trough currently over western Australia approaches the storm. This is likely to cause a turn to the south and maybe even southeast (which is similar to a northerly “poleward” turn in the Northern Hemisphere). The official JTWC forecast, shown below, shows this turn.
Figure 3: Official JTWC forecast for Ita.
The GFS model, along with its ensembles, support this scenario. The normally reliable ECMWF model has a different solution, as it pushes Ita farther into the trough and out into the Gulf of Carpentaria. This seems to be an unlikely solution, as tropical cyclones can’t just steer through a trough like the ECMWF shows. The JTWC is banking heavily on the GFS solution, and my forecast will go in that direction as well. The intensity forecast from the JTWC indicates strengthening all the way up until landfall. Sea surface temperatures in Ita’s path are a favorable 28-29C, dry air is not an issue, and shear is fairly light, generally under 10kts, along its path. These are all factors that point to strengthening. Currently, Ita looks a bit disorganized, and I think strengthening will be slow for at least the next day or so as it works some inner core issues out. Hints of an eye have appeared on microwave imagery but not on conventional satellite imagery yet. Beyond this time, as it nears landfall, more significant strengthening is possible, though not certain. The ECMWF only deepens Ita to about 985mb by the time it reaches what should be its southward turning point. This may be due to the unreasonably weak initialization of 1000mb, which could also explain the likely incorrect track forecast. The ECMWF does deepen Ita to near 960mb in the Gulf of Carpentaria. The GFS, meanwhile, deepens Ita to near 965mb by the time it turns south, which seems fairly reasonable. My forecast, track and intensity, is shown below.
Figure 4: My forecast for Ita. Please remember this is not an official forecast and should not be used for personal decisions. My projected track is the blue line, with the surrounding black lines being a cone of uncertainty and the lines through the middle being intensity checkpoints.
Like the JTWC, I am favoring the south turning track like the GFS shows. I am a little more south for the most part, including the landfall location, as the trough should be fully affecting the storm by that time. I am a bit farther inland in the longer range, however, as Ita may get somewhat stuck inland. It is possible, however, that Ita will re-emerge over water and restrengthen, especially if it tracks less far inland. The GFS shows some reintensification over water, so this will have to be watched. In terms of intensity, I am a bit below the JTWC for peak intensity, forecasting a peak of 115mph instead of their forecast of about 125mph. This isn’t a big difference, as I just don’t think the environment quite supports a 125mph storm. Nonetheless, wind, storm surge, and heavy rain will all be threats to affected areas. Ita will be speeding up by the time it makes landfall however, so this will help things somewhat. Once again, anyone in the areas that may be affected should remain advised of the latest information on this potentially dangerous storm.
Thank you as always for reading. This will likely be my only post on Ita, though I may post some updates in the comments section. Your comments and updates are always welcome as well. Have a great week!
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.