Tropical weather analysis - July 21, 2014

By: KoritheMan , 3:43 AM GMT on July 22, 2014

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Notice: All forecasts presented here are based upon my own knowledge of atmospheric dynamics. They are created using my knowledge of the various computer models, satellite interpretation, and other tools and parameters. These forecasts, while striving to be accurate, are not intended to supersede predictions by the National Hurricane Center. Always follow NWS protocol and forecasts.

Tropical Depression Two

The tropical wave that has marched through the Atlantic over the last few days became a tropical depression today. As of the 0300Z NHC advisory, the following information was posted on the storm:

Wind: 35 mph, with higher gusts
Location: 12.0°N 45.1°W
Movement: W at 16 mph
Pressure: 1012 mb

The satellite signature of this small depression is certainly not impressive. There is a small area of deep convection near the apparent center, with microwave data throughout the evening showing some weak fragmented curved bands to the north and south of the center. Satellite estimates do not currently support tropical storm strength. A recent partial ASCAT pass raises some doubt if the circulation is closed, but there is a frequent inhibition with that instrument to capture closed circulations in small depressions.

Figure 1. Latest infrared satellite image of Tropical Depression Two. Image credit: NOAA's Satellite Services Division (SSD).

The prospects for future intensification appear low, although there is still a chance for the system to become a tropical storm over the next 12-24 hours as it heads westward into progressively warmer waters. That possibility notwithstanding, the cyclone is experiencing ample mid-level dry air on the subsident portion of the Atlantic subtropical ridge. In addition, satellite data shows arc clouds emanating westward ahead of the low-level center, signifying subsident flow creating stable sinking air. Despite the seemingly clear cut synoptic picture, the models are split, with the statistical-dynamical LGEM/SHIPS models showing the depression becoming a moderate to strong tropical storm (indeed, the 0z SHIPS without land factored in takes the depression to hurricane strength in four days), while all of the global models dissipate the tropical cyclone as it nears the Caribbean Sea. Given the increasing shear in the eastern Caribbean associated with the mid-oceanic trough -- which is very apparent on evening water vapor analyses -- coupled with the very meager thermodynamic environment, suggests that the global models likely have a better prediction. My forecast follows the NHC prediction of the cyclone dissipating after 72 hours, although it could occur sooner. Although the GFS and ECMWF show the 200 mb flow possibly relaxing as the depression moves north of the Caribbean later on, there will likely be little to be concerned with at that point.

Satellite data suggests that the depression is moving north of the 2100Z NHC forecast track, and the 0300Z track corrected this accordingly. The depression is currently south of a rather strong low- to mid-tropospheric ridge, with UW-CIMSS steering indicating the ridge building westward ahead of the cyclone between 850 and 700 mb. This should promote a continued west to west-northwestward over the next few days. In about 72 hours, the GFS and ECMWF show a mid-level trough developing over the eastern United States, which is likely to cause the depression to slow down and move more toward the northwestward if it survives beyond the expectation I have delineated below. While there is a nonzero chance of a threat to the United States east coast next week if the depression survives, this is an extremely big if, and dissipation in short order is on today's dollar menu. My forecast track is similar to the current NHC track, but to the south of the latest TVCA model consensus.

The depression could spread locally heavy rains and gusty winds to portions of the Lesser Antilles over the next few days, even if it dissipates as a tropical cyclone.

Intensity forecast

Initial 07/22 0300Z 12.0°N 45.1°W 30 kt 35 mph
12 hour 07/22 1200Z 12.3°N 47.0°W 30 kt 35 mph
24 hour 07/23 0000Z 12.7°N 50.0°W 30 kt 35 mph
36 hour 07/23 1200Z 13.4°N 53.6°W 30 kt 35 mph
48 hour 07/24 0000Z 14.5°N 57.2°W 30 kt 35 mph
72 hour 07/25 0000Z 17.2°N 64.1°W 25 kt 30 mph
96 hour 07/26 0000Z: dissipated

Track forecast

Figure 2. My forecast track for Tropical Depression Two.

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2. WunderAlertBot (Admin)
5:19 AM GMT on July 23, 2014
KoritheMan has created a new entry.
1. nigel20
5:20 AM GMT on July 22, 2014
Thanks Kori! I hope that TD2 will provide some drought respite to the eastern Caribbean, no matter how minimal.
Member Since: November 6, 2010 Posts: 14 Comments: 9038

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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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