Tropical weather analysis - September 1, 2014

By: KoritheMan , 4:44 AM GMT on September 02, 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 Five

Tropical Depression Five formed from a tropical wave that has tracked westward across the Atlantic for several days. As of the latest NHC advisory, the following information was posted on the storm:

Wind: 30 mph, with higher gusts
Location: 21.0°N 93.9°W
Movement: NW at 10 mph
Pressure: 1007 mb

The depression appears a little better organized this evening. While there is not a lot of banding, the cyclone is producing cloud tops as cold as -65 to -70C, with this convection expanding in areal coverage and extent over the last couple of hours. An Air Force Reserve reconnaissance aircraft is currently en route to the depression, and should provide a better assessment of the intensity and structure of the tropical cyclone this morning.



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

There is little evidence of upper-level outflow to the north of the cyclone circulation, suggestive of moderate northerly shear on the backside of a shortwave mid- to upper-level trough moving across the central and southern United States, depicted to be around 15 kt on the UW-CIMSS 850-200 mb shear analyses. As this trough progressively moves away, the global models relax the shear over the depression a little, with the GFS even suggesting weak ridging aloft may become collocated near or over the cyclone center during the 12-24 hours preceding landfall. Since satellite data suggests a decrease in northerly shear, this solution does not appear impossible, but there should be enough shear to prohibit rapid strengthening. Water vapor imagery shows dry air near the depression, but it appears to have shrunk considerably from earlier when the depression was first designated. With underlying sea surface temperatures of around 30C, the cyclone certainly has the potential to become a tropical storm prior to landfall along the eastern coast of Mexico. My forecast is above most of the intensity aids, but is similar to the SHIPS through 36 hours before diverging due to passage of the depression over Mexico. Given the limited time over water and continued northerly shear, the depression likely does not have enough time to become a hurricane. Tropical storm warnings remained hoisted for the eastern Mexican coastline (shown below), however, and interests in the warned area should be vigilant for tropical storm force winds and very heavy rainfall capable of causing flash flooding and mudslides in areas of enhanced terrain.

The depression appears to be moving toward the west-northwest under a distant ridge over the northern Gulf of Mexico, albeit with a little bit more of a northerly component than this afternoon. Given the northward reformation of the center noted on satellite imagery, the model guidance has shifted northward at 0z. My forecast track is pretty similar to the latest National Hurricane Center track, but is a little slower due to some of the guidance suggesting that the western portion of the cyclone could brush up against the Sierra Madre mountain range as it nears the coast, which could cause some deceleration and deflection to the track. This also allows the cyclone a little bit more time over water before it comes ashore. Some deceleration could also occur as the depression potentially follows the convection under less shear, a solution which is possible during the enusing 12-18 hours as the northerly shear continues. After landfall, the depression is expected to quickly unravel, with the low-level center dissipating inland over the mountains by 72 hours.

Intensity forecast

Initial 09/02 0300Z 21.0°N 93.9°W 25 kt 30 mph
12 hour 09/02 1200Z 21.5°N 94.8°W 35 kt 40 mph
24 hour 09/03 0000Z 21.9°N 95.9°W 40 kt 45 mph
36 hour 09/03 1200Z 22.4°N 97.4°W 45 kt 50 mph
48 hour 09/04 0000Z 22.6°N 98.4°W 30 kt 35 mph: inland
72 hour 09/05 0000Z: dissipated

Track forecast



Figure 2. My forecast track for Tropical Depression Five.

NHC storm information

000
WTNT35 KNHC 020236
TCPAT5

BULLETIN
TROPICAL DEPRESSION FIVE ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL052014
1000 PM CDT MON SEP 01 2014

...DEPRESSION FORECAST TO SLOWLY STRENGTHEN...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.0N 93.9W
ABOUT 225 MI...365 KM E OF TUXPAN MEXICO
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* TUXPAN TO LA PESCA MEXICO

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA...IN THIS CASE WITHIN
THE NEXT 24 TO 36 HOURS.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1000 PM CDT...0300 UTC...THE CENTER OF TROPICAL DEPRESSION FIVE
WAS LOCATED NEAR LATITUDE 21.0 NORTH...LONGITUDE 93.9 WEST. THE
DEPRESSION IS MOVING TOWARD THE NORTHWEST NEAR 10 MPH...17 KM/H.
A TURN TOWARD THE WEST-NORTHWEST IS EXPECTED ON TUESDAY. ON THE
FORECAST TRACK...THE CENTER WILL APPROACH THE COAST OF MEXICO WITHIN
THE WARNING AREA BY TUESDAY NIGHT...AND MOVE INLAND BY WEDNESDAY
MORNING.

MAXIMUM SUSTAINED WINDS ARE NEAR 30 MPH...45 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT DAY OR
SO...AND THE DEPRESSION IS FORECAST TO BECOME A TROPICAL STORM ON
TUESDAY.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB...29.74 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE RAINFALL AMOUNTS
OF 3 TO 6 INCHES WITH ISOLATED MAXIMUM AMOUNTS OF 10 INCHES ACROSS
SOUTHERN TAMAULIPAS...NORTHERN VERACRUZ...AND EASTERN SAN LUIS
POTOSI MEXICO THROUGH WEDNESDAY EVENING. THIS RAINFALL COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES IN AREAS OF MOUNTAINOUS
TERRAIN.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED WITHIN THE WARNING
AREA BY LATE TUESDAY.


NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...100 AM CDT.
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER BROWN

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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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