TS Cosme expected to become a hurricane, potential for Atlantic development

By: wxchaser97 , 1:19 PM GMT on June 25, 2013

TS Cosme
Tropical Storm Cosme continues to organize as to heads to the west-northwest. Since my update from last night, a uniform CDO has formed fully around the center. Also an inner core is developing with an eye starting to pop out. While there hasn't been a recent microwave pass, we know an eyewall is developing. There is banding around and away from the center as the storm is pulling in a lot of moister. This is still looking like a Western Pacific tropical cyclone instead of an Easter Pacific one. Satellite intensity estimates show Cosme approaching hurricane to strength or already at hurricane strength. SAB numbers are at T3.5, UW-CIMSS ADT numbers are at 3.7 with 59kt winds, and SSD ADT numbers are at 4.1 with 67.4kt winds. I say Cosme is a 70mph TS to 75mph hurricane. No matter what, Cosme is strengthening, is nearing hurricane strength, and will be a hurricane later today. The latest storm info and satellite image can be found below.

2:00 AM PDT Tue Jun 25
Location: 16.5°N 109.5°W
Moving: WNW at 16 mph
Min pressure: 994 mb
Max sustained: 65 mph

Forecast for TS Cosme
TS Cosme will become a hurricane sometime later today. The evidence is increasing that it is very close to, if not already, one. It is still in a favorable environment for strengthening, but that won't last for long. TCHP values are already beginning to drop, and SST's will be soon to follow. However, waters are still far above the 26C threshold, at 28.6C per the 06z SHIPS diagnostic message, so there is more than enough fuel. 700mb-500mb relative humidity values are still high, above 80%, and are expected to stay that way for the next day. After that, they will begin to slowly fall as Cosme gets into a drier environment, but it's expansive moister field should help the storm. Wind shear is still sitting around 10kts, which is favorable for intensification. If it wasn't for Cosme's very large size, this would be a hurricane right now. Since Cosme remains in a favorable environment, I expect steady strengthening up to the 24hr mark. After that, water temps dip below the 26C threshold and weakening should begin. SST's really drop off after about 3 days and rapid weakening, which is also shown by intensity models, should begin. I expect the post-tropcical transition to begin around 84hrs, with it becoming post-tropical at 96hrs and degenerating to a remnant low sometime after that. Once again, my intensity forecast is mostly a blend with the SHIPS and the LGEM, but my peak is slightly higher than most guidance. I expect a peak of 85mph, due to strengthening trends, followed by steady weakening afterward. It is possible that at the 36hr mark that Cosme may be a strong tropical storm, but at this time I think it will remain, barely, a hurricane at that time.

Cosme's forecast track has not changed much since it first formed. Cosme is beginning to make the turn to the WNW just as planned. This is because of a strengthening mid-level ridge to its north. This ridge is only expected to amplify more as over the next day or so as Cosme heads to the WNW. The east-to-west (clockwise) flow on the south side of the ridge will continue to turn Cosme toward the west with time. As that flow strengthens, Cosme will also begin to speed up some. All the models are still in agreement with the 5 day track of Cosme. They continue the WNW motion with a gradual turn to the west after day 2. At the end of the forecast period, there may be a slight WSW movement, but I am mostly expecting a westward track in the latter part of the forecast. I remain mostly in line with the current NHC track forecast, maybe being slightly north at times. All the models, the NHC, and me are in agreement as the pattern is a cut 'n dry, you know what will happen, situation, which is nice. this means that the projected impacts are the same as I've been previously saying, some rain, waves, wind, and rips for the Mexican coast, and some possible shower impacts for Hawaii from the remnants. Other than that, Cosme won't affect any land areas directly.

INIT 25/1200Z 55 KT 65 MPH
12H 25/0000Z 70 KT 80 MPH
24H 26/1200Z 75 KT 85 MPH
36H 26/0000Z 65 KT 75 MPH
48H 27/1200Z 50 KT 60 MPH
72H 28/1200Z 35 KT 40 MPH
96H 29/1200Z 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 30/1200Z 25 KT 30 MPH...POST-TROP/REMNT LOW

Atlantic Development Potential
While the Eastern Pacific is active right now, the Atlantic basin should get in on the action soon. As we have been talking for about for a while now, a MJO pulse is propagating across the globe right now. This means that there will be a couple areas that could develop. First, is a system that could get going in the far NW Caribbean/BOC. This system would occur during the very last days of June and the beginning of July. The GFS and its ensembles show lowering pressures in the BOC and Gulf of Honduras in about a week. This could turn into a Barry-type storm if one formed, but possibly go farther north. A trough should be located over the Great Lakes in the beginning of July as riding will be located in the western US and off the east coast. This should help pull a system toward the US, unless it remains too far south. The GEM is showing a strong TS to a lower-end hurricane hitting the gulf coast in just over a week. While this definitely isn't likely, I wouldn't ignore the GEM either as it has been very good with sniffing out development so far this season. The GEM has been consistent for at least the past 4 runs with showing a strong TS to minimal hurricane hitting the gulf coast. I would still like another model or two to hope on board with this before saying there is a good chance of that happening, but it is something to watch.

The next area to watch for development would be the Caribbean. As the MJO gets into octants 1 and 2, this promotes upward motion and increased convection in the Atlantic basin. With this means the increased chance of a tropical cyclone forming. Also the strong tropical waves are good for helping the chances of tropical development. One my also help with the formation of the possible storm in the first paragraph. SST's are warm in the Caribbean with good TCHP and moister would be abundant, as already noted with this pulse. Shear is running at or slightly above normal due to the TUTT in the SE Atlantic, but if it can move to the north shear will relax. This means a tropical wave could develop with the right conditions. This is something to watch and see when/if the models start to show anything. My forecast for 2-3 tropical cyclones with our first hurricane remains unchanged for July. There is also the potential for some Cape-Verde like development later into July as the MJO works to the east and the waves stay stronger than normal. Also, a quick storm could spin up at anytime from a dying front or a cold-core low becoming a warm-core system over time. We really have to begin to watch the Atlantic for development even though July is a relatively quiet month.

Have a good day everyone and I'll have a new update on Cosme tonight.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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3. WunderAlertBot
7:53 AM GMT on June 26, 2013
wxchaser97 has created a new entry.
Member Since: December 31, 1969 Posts: Comments:
2. wxchaser97
4:42 PM GMT on June 25, 2013
Quoting GeorgiaStormz:
post about it on wx page....SSD floater or wu sat.....i'm too lazy.....

where's wh98?
Ok, I will.
Not on WU...lol. He'll show up eventually.
Member Since: December 31, 1969 Posts: Comments:
1. GeorgiaStormz
1:50 PM GMT on June 25, 2013
post about it on wx page....SSD floater or wu sat.....i'm too lazy.....

where's wh98?
Member Since: December 31, 1969 Posts: Comments:

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I'm a CMU Honors student and love meteorology and extreme weather. I've been fascinated by weather since I was 5, and plan on becoming a meteorologist

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