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Tropical Storm Cosme approaching hurricane intensity but poses no serious threat

By: TropicalAnalystwx13 , 3:11 AM GMT on June 25, 2013

Tropical Storm Cosme is well on its way to hurricane intensity this evening following classification early this morning. As of the latest advisory from the National Hurricane Center, Cosme was located within 30 nautical miles of 15.9°N 107.9°W, or about 320 miles southwest of Manzanillo, Mexico. Maximum sustained winds were up to 65 mph and the minimum barometric pressure had fallen to 994 millibars. The system was tracking northwest at 14 mph. Recent satellite loops reveal a well-organized tropical cyclone, with deep convection over the center and south of it in a spiral band that extends well out from the storm. Recent microwave imagery shows a developing inner core with Cosme, depicting a banding feature and likely eyewall wrapping three-quarters around the center of circulation. Satellite intensity estimates from UW-CIMSS-ADT and SAB have remained nearly steady near T3.6/57 knots and T3.0/45 knots, respectively, but estimates from SSD-ADT have risen to T4.0/65 knots. Cosme is approaching hurricane intensity and is forecast to reach it early tomorrow morning.

Figure 1. Visible satellite imagery of an intensifying Tropical Storm Cosme at 20:15z.

Forecast for Cosme
Tropical Storm Cosme, after intensifying slower than forecast two days ago, has strengthened quite a bit more than I originally forecast today. Shear seems to have abated some based on satellite trends today, and indeed, the latest SHIPS file analyzed 4 knots of shear atop the cyclone. Cosme remains situated above sea surface temperatures in excess of 29°C and within a moist environment with 700-500mb Relative Humidity values at or above 87%. These conditions are sufficiently favorable for steady if not quick intensification, but Cosme's large size may deter rapid deepening. Considering trends today, I have raised my forecast from yesterday and now predict the cyclone to peak as a strong Category 1 in 24 hours or so. After this time, the storm is expected to cross the 26°C isotherm, enter a region of more stable air, and be deprived of any ocean heat content from below. Accordingly, Cosme is expected to lose hurricane intensity in roughly 48 hours and continue to rapidly weaken thereafter. A majority of the model guidance indicates the storm will weaken to a tropical depression in 84 hours or less; however, due to my forecast being slightly higher than a majority of the guidance, I am expecting the storm to lose that status a little later than indicated. Cosme is expected to become a remnant low at the end of the forecast period.

Tropical Storm Cosme continued to move towards the northwest, paralleling the coastline of Mexico, in response to a weakness to the storm's northwest. A mid-level ridge of high pressure is expected to intensify over the subsequent 24 hours; this should induce a gradual west-northwest bend in Cosme's track while steadily accelerating it. By days three and four, a due west and perhaps west-southwest bend is expected as the rapidly decreasing [in intensity] tropical cyclone becomes embedded within the swift east-to-west flow across the Pacific Ocean. My forecast track is a little quicker than yesterday and remains ever so slightly north of the latest National Hurricane Center track forecast. It is in agreement with a majority of the statistical and dynamical models. While Cosme is not expected to make a direct landfall on any landmass, its large size – with the circulation radius extending out over 300 miles and tropical storm-force winds extending out 175 miles – may produce locally heavy rainfall from Mazatlan to Ixtapa. Constant gale-force winds are expected to produce higher-than-average wave heights along the coastline, and there is a high risk for life-threatening rip currents.


INIT 25/0300Z 15.9N 107.9W 55 KT 65 MPH
12H 25/1200Z 16.8N 109.9W 65 KT 75 MPH
24H 26/0000Z 17.7N 112.3W 75 KT 85 MPH
36H 26/1200Z 18.2N 114.6W 65 KT 75 MPH
48H 27/0000Z 18.9N 117.0W 55 KT 65 MPH
72H 28/0000Z 20.2N 122.2W 40 KT 45 MPH
96H 29/0000Z 20.5N 127.1W 30 KT 35 MPH
120H 30/0000Z 20.4N 132.1W 25 KT 30 MPH...POST-TROP/REMNT LOW

Elsewhere, no tropical cyclone development is expected in the East Pacific over the next two days. I will have a blog on Cosme, my thoughts for the Atlantic hurricane season, and potential July development tomorrow,


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

Reader Comments

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3. WunderAlertBot (Admin)
4:06 AM GMT on June 26, 2013
TropicalAnalystwx13 has created a new entry.
2. 1344
3:29 AM GMT on June 25, 2013
I have nothing to whine about :P Not bad TA.
Member Since: December 31, 1969 Posts: Comments:
1. Astrometeor
3:13 AM GMT on June 25, 2013
Glad to see someone here types faster than Isaac's typing 5-word/minute speed.

Thanks for the blog Cody.
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About TropicalAnalystwx13

Small town USA guy. Politics nerd. Soccer fan. Interested in eyewalls, deformation zones, and hook echos.

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