TropicalAnalystwx13's WunderBlog

Unforeseen circumstance: Tropical Storm Alvin weakening, dissipation likely soon

Posted by: TropicalAnalystwx13, 03:05 AM GMT on mai 17, 2013

Tropical Storm Alvin, the first named storm of the 2013 Pacific hurricane season, developed well south of the coastline of Mexico last night as a result of an area of low pressure that formed several days prior, west of Guatemala. At the time of formation, Alvin was a well-developed tropical cyclone, with fantastic banding and upper-level outflow. The same cannot be said tonight, unfortunately. Strong westerly wind shear on the order of 20 to 25 knots, not foreseen by the SHIPS nor the global models, abruptly halted the cyclone's intensification process last night, and the center became exposed on conventional satellite imagery this morning. Throughout the day, Alvin has continued to degrade, with weakening and shabby convection. The vigorous low-level center seen yesterday evening is no longer visible; in fact, an ASCAT pass from this evening revealed an open circulation associated with Alvin as it has become part of the Intertropical Convergence Zone once again. For continuity purposes, the National Hurricane Center continues to write advisories on the storm, though I suspect these will cease in the morning. The latest information on the storm is as follows: maximum sustained winds of 40 mph, minimum barometric pressure of 1006 millibars, movement towards the west-northwest at 14 mph.

Figure 1. MODIS image of Tropical Storm Alvin at the time of classification.

Figure 2. Enhanced visible satellite image of Tropical Storm Alvin this afternoon. At the time, maximum sustained winds were estimated at 45 mph, with stronger gusts.

Forecast for Alvin
The forecast for Tropical Storm Alvin really is not complicated at this point. The storm has become embedded within the Intertropical Convergence Zone once again and likely no longer contains a closed circulation. If no evidence of a closed circulation is found within the next 12 hours, it is very likely the National Hurricane Center will discontinue advisories on the cyclone, as this is one of the core criterion of a tropical system. No re-intensification is likely due to continued, strong westerly wind shear. The track forecast is also simple. Alvin, or what's left of it, is expected to continue west-northwest for the next two days or so, steered around the southwestern periphery of a large subtropical ridge over Mexico. By 72 hours, the global models advertise a weakness over the Southwest United States, created by an approaching trough. All model solutions show the low-level and mid-level centers of Alvin splitting at this point, with the former continuing westward, caught in the east-to-west flow of the Pacific, and the latter being drawn north into the trough. Both are expected to dissipate by the end of the forecast period. Congratulations to the CMC and ECMWF, both of which never showed appreciable intensification of this cyclone.

...MAX WINDS...

INIT 17/0300Z 35 KT 40 MPH
12H 17/1200Z 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 18/0000Z 25 KT 30 MPH...POS-TROP/REMNT LOW
36H 18/1200Z 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 19/0000Z 20 KT 25 MPH...POST-TROP/REMNT LOW
72H 20/0000Z 15 KT 20 MPH...POST-TROP/REMNT LOW
96H 21/0000Z 15 KT 20 MPH...POST-TROP/REMNT LOW
120H 22/0000Z...DISSIPATED

I'll have a new blog on the potential for development in the eastern Pacific and Atlantic tomorrow,

TropicalAnalystwx13

Categories:Tropical Cyclones of 2013 Tropical Weather

Updated: 03:25 AM GMT on mai 17, 2013

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ALVIN! The first named storm of the 2013 Pacific hurricane season develops on cue

Posted by: TropicalAnalystwx13, 10:13 PM GMT on mai 15, 2013

Not dissimilar to the 2012 Pacific hurricane season, which featured both Tropical Storm Aletta and Hurricane Bud in May, we are once again starting the hurricane season right on cue. What was once Invest 90E intensified into Tropical Depression One-E early this morning and further to Tropical Storm Alvin as of the latest update. The most recent information from the National Hurricane Center states maximum sustained winds have increased to 40 mph, and the minimum bar...

Categories:Tropical Cyclones of 2013 Tropical Weather

Updated: 10:20 PM GMT on mai 15, 2013

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Invest 90E likely to become Alvin; long-range development possible in both basins

Posted by: TropicalAnalystwx13, 02:13 AM GMT on mai 15, 2013

The Pacific hurricane season is jumping the gun once again this year, with an area of disturbed weather—dubbed Invest 90E, the first invest of the season—positioned several hundred miles south-southwest of Acapulco, Mexico. Satellite loops reveal the system remains relatively disorganized this evening, with weak and overall unconsolidated convection (it is in the process of organizing, however). In addition, Invest 90E remains a part of the monsoon trough and In...

Categories:Tropical Cyclones of 2013 Tropical Weather

Updated: 02:15 AM GMT on mai 15, 2013

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2013 Atlantic hurricane season: busy and dangerous

Posted by: TropicalAnalystwx13, 12:09 AM GMT on mai 13, 2013

+16

It feels like the 2012 Atlantic hurricane season just ended, and yet it's already time to start talking about the upcoming one. In summary, the 2013 Atlantic hurricane season is expected to draw out the almost continuous streak of Atlantic hurricane seasons above-average since 1995. A total of 16–19 named storms, 8–12 hurricanes, and 3–5 major hurricanes are expected, with an Accumulated Cyclone Energy (ACE) index of >150 units. Due to the positive Atlantic tr...

Categories:Tropical Weather Tropical Cyclones of 2013

Updated: 12:11 AM GMT on mai 13, 2013

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2013 Atlantic hurricane season preliminary forecast

Posted by: TropicalAnalystwx13, 12:29 AM GMT on martie 12, 2013

+15

Well...it's March. Daylight Saving Time was yesterday, meaning we have lost an hour of sleep. But it also means we're getting closer to hurricane season, which now begins in less than three months. Speaking of the season...this one looks to be active. The variables I used for my forecast, an overview of them, and what they are forecast to be for this upcoming hurricane season are listed below.

El Niño-Southern Oscillation (ENSO)

One of the mos...

Categories:Tropical Weather Tropical Cyclones of 2013

Updated: 10:44 PM GMT on martie 22, 2013

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