Basement-dwelling pseudo-otaku with a thrill for forecasting on the side.
By: KoritheMan , 2:31 AM GMT on October 05, 2013
Tropical Storm Karen continues to struggle against strong vertical shear. As of the 0000Z NHC intermediate advisory (actual 0300Z full advisory is coming up soon), the following information was available on Karen:
Wind: 50 mph, with higher gusts
Location: 25.9°N 90.3°W
Pressure: 1002 mb
There isn't much new to say about Karen, or this pathetic excuse of a hurricane season. Satellite images show the low-level center has become completely exposed once again, after a brief period of reorganization earlier in the day. The deep convection is confined to the vigorous mid-level center located about 125 miles to the east of Karen's actual center.
Figure 1. Latest infrared satellite image of Tropical Storm Karen. Image credit: NOAA's Satellite Services Division (SSD).
The environment ahead of Karen does not appear particularly promising for intensification, with water vapor images continuing to show strong westerly shear affecting the cyclone in association with a seasonably deep longwave trough moving across the central United States. Upper air soundings over the United States indicate that the environmental airmass to the west of Karen is also exceptionally dry. These factors argue against reintensification of Karen despite the very deep warm water over the northern Gulf of Mexico. Although the GFS, after incorporation of data from the NOAA G-IV surveillance mission conducted earlier shows the 200 mb winds decreasing a little bit as Karen approaches the coast, there does not currently appear to be much evidence of this happening. Under the presumption that increasing upper divergence associated with the right entrance region of the upper-level trough increases over the tropical storm during the next 24-48 hours, Karen should be able to maintain the status quo all the way to landfall, but actual reintensification is unlikely. An alternate scenario is that the cyclone decays into a remnant low before reaching the coast, as happened with Tropical Storm Bonnie in 2010.
Karen's motion has become easy to determine since the center is in plain view once again. The cyclone has been moving somewhat erratically, but the general motion over the last few hours appears to be north-northwest. Karen is between a deep-layer ridge over the eastern United States, and a broad mid-latitude trough over the central United States. This evolution argues against little deviation from current trends, and the cyclone is expected to pass near or over the southeastern Louisiana coast in the next 36 hours. After that time, Karen is forecast to become well-embedded in the high latitude westerlies and accelerate northeastward over the southeastern United States. The guidance is in better agreement on the more westward motion toward Louisiana over the succeeding 36 hours than they were yesterday, and my forecast is largely the same as the one I published this morning, albeit a little farther west of the current NHC prediction and model consensus due to the vertically shallow nature of Karen's vortex. It should be noted that there is some indication in the upper air soundings over the northern Gulf Coast and southeastern United States that large-scale ridging has increased above 850 mb compared to 24 hours ago, and this could keep Karen on a more westward track even if convection redevelops.
Unless the shear decreases before landfall, the main impact from Karen will be to the east of the center, in the form of tropical storm force winds, high surf, minor coastal flooding, isolated tornadoes, and heavy rain.
Intensity forecast and positions
INITIAL 10/05 0000Z 25.9°N 90.3°W 45 KT 50 MPH
12 hour 10/05 1200Z 26.7°N 90.6°W 45 KT 50 MPH
24 hour 10/06 0000Z 27.7°N 90.5°W 45 KT 50 MPH
36 hour 10/06 1200Z 28.9°N 89.7°W 45 KT 50 MPH
48 hour 10/07 0000Z 30.4°N 87.7°W 35 KT 40 MPH...INLAND
72 hour 10/08 0000Z 32.7°N 82.6°W 30 KT 35 MPH...POST-TROPICAL/EXTRATROPICAL
96 hour 10/09 0000Z...ABSORBED
Figure 2. My forecast track for Karen.
NHC storm information
WTNT32 KNHC 042337
TROPICAL STORM KAREN INTERMEDIATE ADVISORY NUMBER 7A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122013
700 PM CDT FRI OCT 04 2013
...KAREN HESITATES IN THE CENTRAL GULF OF MEXICO...
SUMMARY OF 700 PM CDT...0000 UTC...INFORMATION
ABOUT 235 MI...375 KM SSW OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 270 MI...430 KM SSE OF MORGAN CITY LOUISIANA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY...
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* MORGAN CITY LOUISIANA TO THE MOUTH OF THE PEARL RIVER
A TROPICAL STORM WATCH IS IN EFFECT FOR...
* METROPOLITAN NEW ORLEANS
* LAKE MAUREPAS
* LAKE PONTCHARTRAIN
* EAST OF THE MOUTH OF THE PEARL RIVER TO INDIAN PASS FLORIDA
A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.
A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA...GENERALLY WITHIN 48 HOURS.
INTERESTS ELSEWHERE ALONG THE NORTHEASTERN COAST OF THE GULF OF
MEXICO SHOULD MONITOR THE PROGRESS OF KAREN.
FOR STORM INFORMATION SPECIFIC TO YOUR AREA...INCLUDING POSSIBLE
INLAND WATCHES AND WARNINGS...PLEASE MONITOR PRODUCTS ISSUED BY
YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.
DISCUSSION AND 48-HOUR OUTLOOK
AT 700 PM CDT...0000 UTC...THE CENTER OF TROPICAL STORM KAREN WAS
LOCATED NEAR LATITUDE 25.9 NORTH...LONGITUDE 90.3 WEST. KAREN HAS
BEEN NEARLY STATIONARY DURING THE PAST COUPLE OF HOURS...BUT THE
CYCLONE SHOULD RESUME A NORTH-NORTHWEST TRACK NEAR 7 MPH...11 KM/H
LATER TONIGHT. A TURN TOWARD THE NORTH WITH A DECREASE IN FORWARD
SPEED IS EXPECTED ON SATURDAY...AND A TURN TOWARD THE NORTHEAST
WITH AN INCREASE IN FORWARD SPEED IS EXPECTED ON SUNDAY. ON THE
FORECAST TRACK...THE CENTER OF KAREN IS EXPECTED BE NEAR THE COAST
IN THE TROPICAL STORM WARNING SATURDAY NIGHT.
DATA FROM AN AIR FORCE RESERVE AND NOAA HURRICANE HUNTER AIRCRAFT
INDICATE THAT MAXIMUM SUSTAINED WINDS REMAIN NEAR 50 MPH...85
KM/H...WITH HIGHER GUSTS. LITTLE CHANGE IN STRENGTH IS FORECAST
TONIGHT AND SATURDAY. SLIGHT STRENGTHENING IS POSSIBLE SATURDAY
NIGHT AND SUNDAY.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES...220
KM...MAINLY TO THE NORTH AND EAST OF THE CENTER.
THE LATEST MINIMUM CENTRAL PRESSURE BASED ON DATA FROM THE AIRCRAFT
IS 1002 MB...29.59 INCHES.
HAZARDS AFFECTING LAND
WIND...TROPICAL STORM CONDITIONS ARE EXPECTED WITHIN PORTIONS OF THE
WARNING AREA BY SATURDAY AFTERNOON. TROPICAL STORM CONDITIONS ARE
POSSIBLE IN PORTIONS OF THE WATCH AREA SATURDAY NIGHT AND SUNDAY.
STORM SURGE...THE COMBINATION OF STORM SURGE AND THE TIDE WILL CAUSE
NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING WATERS.
THE WATER COULD REACH THE FOLLOWING HEIGHTS ABOVE GROUND IF THE
PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE...
WEST OF THE MISSISSIPPI RIVER TO TERREBONNE BAY...1 TO 3 FT
MOUTH OF THE MISSISSIPPI RIVER TO THE PEARL RIVER...3 TO 5 FT
EAST OF THE PEARL RIVER TO WEST OF APALACHEE BAY...1 TO 3 FT
APALACHEE BAY INCLUDING CEDAR KEY...2 TO 4 FT
SOUTH OF APALACHEE BAY TO TAMPA BAY...1 TO 2 FT
THE HIGHEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST...WHERE THE
SURGE WILL BE ACCOMPANIED BY DANGEROUS WAVES. SURGE-RELATED
FLOODING DEPENDS ON THE RELATIVE TIMING OF THE SURGE AND THE TIDAL
CYCLE...AND CAN VARY GREATLY OVER SHORT DISTANCES. FOR INFORMATION
SPECIFIC TO YOUR AREA...PLEASE SEE PRODUCTS ISSUED BY YOUR LOCAL
NATIONAL WEATHER SERVICE OFFICE.
RAINFALL...KAREN IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 3 TO 6
INCHES OVER PORTIONS OF THE CENTRAL AND EASTERN GULF COAST THROUGH
SUNDAY NIGHT...MAINLY NEAR AND TO THE RIGHT OF THE PATH OF THE
CENTER. ISOLATED STORM TOTAL AMOUNTS OF 10 INCHES ARE POSSIBLE.
NEXT COMPLETE ADVISORY...1000 PM CDT.
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
Comments will take a few seconds to appear.