Tropical weather analysis - November 19, 2013

By: KoritheMan , 2:37 AM GMT on November 20, 2013

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Melissa

Melissa continues as a subtropical storm over the central Atlantic, and is no threat to land areas. As of the latest NHC advisory, the following information was available on the storm:

Wind: 65 mph, with higher gusts
Location: 33.0°N 53.7°W
Movement: NE at 16 mph
Pressure: 982 mb

The satellite presentation of Melissa has degraded rather significantly this evening. Convective cloud tops have warmed considerably, with only a very fragmented band of tops colder than -40C a short distance north of the center. While convection has been shallow, what convection has existed has been ongoing fairly close to the center in bands. This would ordinarily argue for tropical characteristics, but water vapor imagery suggests that Melissa is still deeply involved with a weakening upper cold low. Satellite estimates have not changed much, with TAFB still giving a classification of 3.0/45 kt. I should note that the 0z ATCF file from the NHC shows Melissa as a 50 kt storm, rather than a 55 kt storm, so I used that for the initial intensity below.



Figure 1. Latest infrared satellite image of Subtropical Storm Melissa. Image credit: NOAA's Satellite Services Division (SSD).

Time is just about out for Melissa to become a tropical cyclone. AMSU temperature profiles indicate that the cyclone has a rather deep warm core at about 500 mb, but the upper troposphere has been slow to warm above that level over the last few days, likely because Melissa remains involved with the upper low, which has in itself helped to inject dry air and subsident flow into the system. The dry air, in turn, has not allowed for Melissa to generate persistently cold thunderstorms to sufficiently warm the upper troposphere and make the transition to a tropical cyclone; there are still no signs of anticyclonic outflow, which is another indicator that Melissa remains subtropical. While the SHIPS model's analysis of 24C underlying sea surface temperatures are likely falsely inflated toward the cold side, Melissa has already crossed the 26C isotherm. From this point onward, waters cool significantly, which should put an end to additional intensification, and with any luck, the epic fail that is the 2013 Atlantic hurricane season. The global model guidance continues to indicate that the environment over the north Atlantic will not be adequately baroclinic to promote some non-tropical restrengthening later in the period; instead, Melissa is likely to weaken over cold water and strong shear as it remains quite distant from an upper-level trough moving over the western Atlantic. Most of the guidance suggests that the cyclone will become absorbed into the deepening trough by the 96 hour mark, and it is possible that the merger could be complete in as little as 72 hours. It is possible that Melissa could become a non-convective remnant low at any time over the next 24 hours, prior to the point of extratropical transition.

Melissa's center appears to be somewhat broad based on microwave and satellite data, but lacking convection it is still reasonably easy to follow. Melissa appears to still be moving northeastward ahead of the aforementioned trough, but a comparison of the current motion to the track contained in the previous NHC advisory package suggests that Melissa could be moving ever so slightly to the right of the track, so my forecast was shifted a little eastward to reflect this. The models have come into better agreement on where Melissa is going to move in the latter portion of the forecast period, with the GFS no longer a western outlier. With the ECMWF and GFS now in tow, confidence in the forecast track at longer ranges has increased. It should be noted that the GFS is still well to the left of the ECMWF at longer ranges, but has come into the fold enough to consider it more or less in synch. My forecast track tonight is significantly east of the one I made yesterday.

Intensity forecast and positions

INITIAL 11/20 0300Z 33.5°N 52.7°W 50 KT 60 MPH
12 hour 11/20 1200Z 35.7°N 48.5°W 50 KT 60 MPH
24 hour 11/21 0000Z 38.0°N 44.7°W 45 KT 50 MPH
36 hour 11/21 1200Z 40.9°N 38.0°W 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
48 hour 11/22 0000Z 43.5°N 30.5°W 40 KT 45 MPH...POST-TROPICAL/EXTRATROPICAL
72 hour 11/23 0000Z 49.4°N 25.6°W 35 KT 40 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 11/24 0000Z...ABSORBED

Track forecast



Figure 2. My forecast track for Melissa.

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3. WunderAlertBot (Admin)
12:15 AM GMT on November 21, 2013
KoritheMan has created a new entry.
2. Astrometeor
6:22 AM GMT on November 20, 2013
Quoting 1. BaltimoreBrian:
Yesterday I thought Melissa would look much better at this time. I didn't explicitly say so but I thought Melissa would be a hurricane at 5 p.m. today. But of course it's 2013.



I was hoping Melissa would become a hurricane, would be a pro for my numbers. But no, it has to remain a STS.
-_-
Member Since: July 2, 2012 Posts: 100 Comments: 10235
1. BaltimoreBrian
2:56 AM GMT on November 20, 2013
Yesterday I thought Melissa would look much better at this time. I didn't explicitly say so but I thought Melissa would be a hurricane at 5 p.m. today. But of course it's 2013.

Member Since: August 9, 2011 Posts: 26 Comments: 8590

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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.