Tropical weather analysis - July 28, 2013

By: KoritheMan , 5:59 AM GMT on July 28, 2013

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Flossie

Tropical Storm Flossie continues to move westward across the central Pacific:

Wind: 50 mph, with higher gusts
Location: 19.0N 143.2W
Movement: W at 20 mph
Pressure: 1000 mb

Although Flossie has already crossed the 26C isotherm, convection has increased again, with a distinct curved band in the western semicircle. In addition, there does not appear to be any substantial vertical shear over the system, with the GFS actually suggesting that the shear will not increase over the storm until about 36-48 hours.



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

The models suggest continued weakening on a gradual basis, but this will likely not come from vertical shear in the immediate future. However, water vapor imagery shows an enormous amount of subsidence ahead of the cyclone, and the SHIPS responds to this by forecasting a continued decrease in relative humidity values. The combination of dry air, cool water temperatures, and then increasing westerly shear as Flossie approaches the Hawaiian Islands should cause the cyclone to slowly weaken. Areal sea surface temperature analyses indicates that sea surface temperatures warm in the vicinity of the Hawaiian Islands, so it is likely that Flossie will maintain at least minimal tropical storm strength as it makes landfall on the Big Island on Monday evening.

Flossie is south of a well-established mid-level ridge over the central Pacific. Water vapor images suggest a lot of zonal flow developing to the north of the Hawaiian Islands, a similar signature of which was confirmed in recent UW-CIMSS steering analyses. This implies a strengthening of the ridge, so Flossie is likely to turn due west near 150W. Virtually all of the guidance takes Flossie over the Big Island on Monday evening. The GFS and ECMWF have come into better agreement on the timing, which increases confidence in the forecast track.

A tropical storm watch has been issued for Hawaii and Maui counties, and interests in the watch area should begin preparation for tropical storm force winds, power outages, and very heavy rains capable of causing flash flooding. The winds could be especially dangerous in higher elevations, perhaps up to 60 mph in some of the heavier squalls.

5-day intensity forecast

INITIAL 07/28 0300Z 45 KT 50 MPH
12 hour 07/28 1200Z 45 KT 50 MPH
24 hour 07/29 0000Z 40 KT 45 MPH
36 hour 07/29 1200Z 35 KT 40 MPH
48 hour 07/30 0000Z 35 KT 40 MPH...INLAND

I am experimenting with making my track maps look more professional and less sloppy. Since I'm still learning how to use this new program I found to make them, I will withhold on carving such a map for tonight. However, my forecast track is pretty well in line with that of the Central Pacific Hurricane Center, except a bit farther south at longer ranges, taking it over the central portion of the Big Island in 48 hours.

CPHC storm information

WTPA31 PHFO 280232
TCPCP1

BULLETIN
TROPICAL STORM FLOSSIE ADVISORY NUMBER 13
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP062013
500 PM HST SAT JUL 27 2013

...FLOSSIE CONTINUES MOVING WESTWARD TOWARD THE STATE OF HAWAII...

SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...19.0N 143.2W
ABOUT 775 MI E OF HILO HAWAII
MAXIMUM SUSTAINED WINDS...50 MPH
PRESENT MOVEMENT...W OR 275 DEGREES AT 20 MPH
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


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

A TROPICAL STORM WATCH HAS BEEN ISSUED FOR HAWAII AND MAUI COUNTIES.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WATCH IS IN EFFECT FOR...
*HAWAII COUNTY
*MAUI COUNTY

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA WITHIN 48 HOURS.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 500 PM HST...0300 UTC...THE CENTER OF TROPICAL STORM FLOSSIE WAS
LOCATED NEAR LATITUDE 19.0 NORTH...LONGITUDE 143.2 WEST. FLOSSIE IS
MOVING TOWARD THE WEST NEAR 20 MPH...AND THIS MOTION IS EXPECTED TO
CONTINUE FOR THE NEXT 24 TO 48 HOURS.

MAXIMUM SUSTAINED WINDS ARE NEAR 50 MPH WITH HIGHER GUSTS. SOME
WEAKENING IS FORECAST DURING THE NEXT 48 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 175 MILES FROM THE
CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB...29.53 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...HEAVY RAINFALL MAY BEGIN AS EARLY AS MONDAY MORNING OVER
HAWAII COUNTY AND MONDAY AFTERNOON OVER MAUI COUNTY.

WIND...TROPICAL STORM FORCE WINDS ARE EXPECTED AS EARLY AS MONDAY
AFTERNOON.

SURF...LARGE SURF WILL IMPACT EAST FACING SHORES POSSIBLY AS EARLY
AS SUNDAY AFTERNOON WITH THE LARGEST SURF EXPECTED ON MONDAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1100 PM HST.

$$
FORECASTER BURKE

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3. WunderAlertBot (Admin)
7:11 AM GMT on July 29, 2013
KoritheMan has created a new entry.
2. Doppler22
6:15 AM GMT on July 28, 2013
TS watches for Hawaii... not something you see every year. Its kinda cool :p
Member Since: February 13, 2012 Posts: 11 Comments: 3743
1. Bluestorm5
6:04 AM GMT on July 28, 2013
Just shoot me WU Mail if you need help with the map (assuming you're using Paint.NET).
Member Since: August 1, 2011 Posts: 28 Comments: 8009

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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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