Tropical weather analysis - September 22, 2012

By: KoritheMan , 5:35 AM GMT on September 22, 2012

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Remnants of Nadine

After many days of diligence, Nadine finally made the transition to a post-tropical cyclone tonight. As of the final NHC advisory, the following information was posted on the post-tropical low:

Wind: 60 mph, with higher gusts
Location: 31.9°N 26.6°W
Movement: SSE at 13 mph
Pressure: 984 mb

A poorly-defined band of convection still persists in the southwest quadrant, but it is well-removed from the center and not well organized.



Figure 1. Latest infrared satellite image of Post-Tropical Cyclone Nadine. Image credit: RAMMB Colorado State University (CSU).

It should be noted that while Nadine is no longer tropical, the GFS and SHIPS continue to forecast a more favorable upper wind environment over the next couple of days; the former even suggests an anticyclone. Since Nadine is heading toward warmer water, regeneration back into a tropical cyclone is a distinct possibility as the low gradually turns east and north over the next day or two.

Probability of development in 48 hours: 30%



Invest 94L

A non-tropical area of low pressure centered about 350 miles east-northeast of Bermuda has become less organized. Upper-level winds are forecast to be only marginally conducive for development as the low recurves. Beyond 36 hours, a sharp increase in westerly shear is anticipated, which should halt any possible accolades from the low.



Figure 3. Latest infrared satellite image of Invest 94L. Image credit: NOAA

Probability of development in 48 hours: 10%



Tropical Depression Thirteen-E

A new tropical depression formed in the Eastern Pacific today from what was previously known as "Invest 93E". The first NHC advisory had the following to say about the system:

Wind: 35 mph, with higher gusts
Location: 13.7°N 107.5°W
Movement: W at 12 mph
Pressure: 1005 mb

As is typical of developing systems, the outer banding seen earlier has decreased, while convection has developed closer to the low-level center. This typically heralds intensification, and I expect the system will be a tropical storm soon.



Figure 4. Latest infrared satellite image of Tropical Depression Thirteen-E. Image credit: NOAA

The environment ahead of the depression looks quite favorable; favorable enough that rapid intensification could occur. The 0z SHIPS rapid intensification parameter shows a 57% chance of a 25 kt increase in wind speed in association with the tropical cyclone, which is five times the sample mean. In about four days, the cyclone is forecast to encounter cooler waters and begin to weaken. Lacking any obvious sign of negativity, I will forecast a 35 kt increase in wind speed over the next 48 hours. However, I am fully prepared to wake up to a storm even stronger than that, in which case my intensity forecast will be revised significantly upward in my next entry.

Water vapor imagery and UW-CIMSS steering data shows that the depression remains south of a well-established subtropical ridge. The global models respond to this thematic pattern by forecasting a general west-northwest motion throughout the next five days. A more poleward bend is possible beyond day three as the system encounters a bigger weakness in the ridge. My forecast is close to the National Hurricane Center official track, albeit slower near the end to account for the aforementioned weakness.

The models have come significantly westward today, and are now in better agreement that this cyclone will not threaten Baja.

5-day intensity forecast

INITIAL 09/22 0300Z 30 KT 35 MPH
12 hour 09/22 1200Z 35 KT 40 MPH
24 hour 09/23 0000Z 45 KT 50 MPH
36 hour 09/23 1200Z 55 KT 65 MPH
48 hour 09/24 0000Z 65 KT 75 MPH
72 hour 09/25 0000Z 75 KT 85 MPH
96 hour 09/26 0000Z 70 KT 80 MPH
120 hour 09/27 0000Z 60 KT 70 MPH

5-day track forecast



Figure 5. My 5-day forecast track for Tropical Depression Thirteen-E.

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5. GeorgiaStormz
1:30 PM GMT on September 22, 2012
Tha blog is hot.
Member Since: February 11, 2012 Posts: 0 Comments: 9760
4. KoritheMan
6:22 AM GMT on September 22, 2012

Quoting wxchaser97:
Thanks Kori, Nadine may come back just so you have to continue to forecast her:)
Why do you think I opted for 30%? The gal's just full of surprises!
Member Since: March 7, 2007 Posts: 602 Comments: 21333
3. KoritheMan
6:21 AM GMT on September 22, 2012

Quoting Civicane49:

Also, thanks for checking out my blog on Iniki today.
No problem. Thanks for taking the time to write it. As I said, it was very informative.
Member Since: March 7, 2007 Posts: 602 Comments: 21333
2. Civicane49
5:51 AM GMT on September 22, 2012
Thanks for the update.

Also, thanks for checking out my blog on Iniki today.
Member Since: July 21, 2011 Posts: 83 Comments: 7167
1. wxchaser97
5:45 AM GMT on September 22, 2012
Thanks Kori, Nadine may come back just so you have to continue to forecast her:). I agree with you on Nadine, 94L, and TD13-E.
Member Since: March 16, 2012 Posts: 127 Comments: 7972

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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