Cloud Stalker: BERTHA STILL A VIGOROUS TROPICAL STORM

Sunday, July 13, 2008

BERTHA STILL A VIGOROUS TROPICAL STORM

000
WTNT32 KNHC 132026
TCPAT2
BULLETIN
TROPICAL STORM BERTHA ADVISORY NUMBER 43
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022008
500 PM AST SUN JUL 13 2008

...BERTHA STILL A VIGOROUS TROPICAL STORM...

A TROPICAL STORM WARNING IS IN EFFECT FOR BERMUDA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED
BY YOUR LOCAL WEATHER OFFICE.

AT 500 PM AST...2100Z...THE CENTER OF TROPICAL STORM BERTHA WAS
LOCATED NEAR LATITUDE 30.2 NORTH...LONGITUDE 63.1 WEST OR ABOUT 175
MILES...285 KM...SOUTHEAST OF BERMUDA.

BERTHA HAS BEEN MEANDERING SINCE YESTERDAY BUT IT APPEARS THAT A
MOTION TOWARD THE NORTHWEST NEAR 2 MPH...4 KM/HR SHOULD FINALLY
BEGIN TONIGHT. A GRADUAL TURN TO THE NORTH IS EXPECTED DURING THE
NEXT 24 TO 36 HOURS. ON THIS TRACK...THE CENTER OF BERTHA IS
EXPECTED TO SLOWLY PASS NOT FAR TO THE SOUTHEAST AND EAST OF
BERMUDA DURING THE NEXT DAY OR SO.

DATA FROM A RECONNAISSANCE PLANE INDICATE THAT MAXIMUM SUSTAINED
WINDS REMAIN NEAR 65 MPH...100 KM/HR...WITH HIGHER GUSTS. LITTLE
CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES...220 KM
FROM THE CENTER.

MINIMUM CENTRAL PRESSURE REPORTED BY A RECONNAISSANCE AIRCRAFT WAS
990 MB...29.23 INCHES.

LARGE SWELLS AND HIGH SURF ARE AFFECTING BERMUDA...AND THESE
CONDITIONS ARE EXPECTED TO PERSIST FOR THE NEXT COUPLE OF DAYS.

THE OUTER BANDS OF BERTHA COULD PRODUCE RAINFALL AMOUNTS IN BERMUDA
OF 2 TO 4 INCHES DURING THE NEXT COUPLE OF DAYS.

REPEATING THE 500 PM AST POSITION...30.2 N...63.1 W. MOVEMENT
TOWARD...NORTHWEST NEAR 2 MPH. MAXIMUM SUSTAINED WINDS...65 MPH.
MINIMUM CENTRAL PRESSURE...990 MB.

AN INTERMEDIATE ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE
CENTER AT 800 PM AST FOLLOWED BY THE NEXT COMPLETE ADVISORY AT 1100
PM AST.

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HAIL (3/4 inch or greater)

Hail can cause significant damage to your vehicle, break windows and damage roofs of homes and businesses.
Hail can cause significant bodily injuries such as broken bones and even blindness if wind blown.
Softball (4.5 inches) sized hail was reported in Lake Wales, Florida on March 30, 1996.
Haildrifts, up to four feet deep of dime to nickel sized hail, occurred in low-lying areas near Zephyrhills, Florida on January 29, 1997.
Hailstones the size of softballs can fall at speeds faster than 100 mph

supercell

Supercells derive their rotation through tilting of horizontal vorticity (an invisible horizontal vortex) caused by wind shear. Strong updrafts lift the air turning about a horizontal axis and cause this air to turn about a vertical axis. This forms the deep rotating updraft, the mesocyclone.
A cap or capping inversion is usually required to form a downdraft of sufficient strength. The cap puts an inverted (warm-above-cold) layer above a normal (cold-above-warm) boundary layer, and by preventing warm surface air from sinking too far, allows one or both of the following:
Air below the cap warms and/or becomes more moist
Air above the cap cools
This creates a warmer, moister layer below a cooler layer, which is increasingly unstable (because warm air is less dense and tends to rise). When the cap weakens or moves, explosive development follows.
In North America, supercells usually show up on Doppler radar as starting at a point or hook shape on the southwestern side, fanning out to the northeast. The heaviest precipitation is usually on the southwest side, ending abruptly short of the rain-free updraft base or main updraft (not visible to radar). The rear flank downdraft, or RFD, carries precipitation counterclockwise around the north and northwest side of the updraft base, producing a "hook echo" that indicates the presence of a mesocyclone.