Tropical weather analysis - July 4, 2014

By: KoritheMan , 7:34 AM GMT on July 04, 2014

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Arthur

Arthur is a dangerous Category 2 hurricane as it made a second landfall in eastern North Carolina. As of the latest NHC position/intensity estimate, the following information was available on Arthur:

Wind: 100 mph, with higher gusts
Location: 35.6°N 75.9°W
Movement: NE at 22 mph
Pressure: 973 mb
Category: 2 (Saffir-Simpson Hurricane Wind Scale)

Satellite and coastal radar data indicate that Arthur is holding its own. Deep convection has been increasing the eastern and northern eyewall, which is not surprising with a northeastward-moving hurricane that's still largely over water. The radar data suggests that Arthur has closed off its eye, although the eyewall convection remains a little weak to the southwest. A pronounced outflow channel has opened up to the north and east of the hurricane in response to increasing upper divergence from an approaching shortwave trough in the westerlies. There is also a lesser outflow channel to the south.



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

Although much of the circulation is overland, some modest intensification remains possible once Arthur gets a little farther away from the coast. The LGEM forecasts about a 5 kt increase in wind speeds over the next 6 hours before leveling off. The atmospheric vertical shear is still momentarily light, and nearby surface observations indicate that the near-storm environment is rather moist. Arthur has moved north of the Gulf Stream, so rapid intensification is not anticipated. But as a reminder, Hurricane Alex intensified in a similar location in 2004 under similar atmospheric processes, and unexpectedly strengthened into a 105 kt major hurricane. Coastal and offshore buoy data indicates that the underlying water temperatures are still around 27C in this area, a little bit warmer than normal for this time of year. This portion of the North Carolina coastal area is rather marshy, which is why Arthur has not weakened; in fact, the radar and satellite signature have improved since the 0300Z NHC advisory several hours ago. Any intensification is likely to occur within the next 6-12 hours, after which time the hurricane will encounter quickly cooling waters, drier air, and a substantial increase in southwesterly to westerly shear. A rather abrupt pace of weakening is forecast subsequent to the 12 hour forecast point, and Arthur is likely to become extratropical in about 36 hours, if not sooner. Forecast points are only provided out to 48 hours due to the limitations of the map I used to create the track forecasts. The global models show Arthur possibly becoming absorbed within a larger extratropical cyclone over the North Atlantic by day five.

There is an outside chance that Arthur briefly reaches Category 3 status after it pulls away from North Carolina. This could occur as baroclinic forcing attendant to the approaching shortwave and associated frontal boundary contribute to additional divergence and forcing. Arthur's expected further acceleration could also assist the strengthening process, or at least maintaining the cyclone at its current intensity for a little while longer.

Arthur has been moving somewhat wobbly this morning, but the general direction has been toward the northeast. Water vapor and UW-CIMSS steering data indicate that Arthur is well-embedded in the mid-latitude westerly flow associated with an approaching shortwave trough and attendant frontal system. A comparison of the 12z and 0z upper air data at Bermuda indicate that heights rose a little on the island during that 12 hour period, which likely contributed to Arthur following the western edge of the cone of uncertainty and making an unexpected landfall on the mainland. Because of this, the 6z guidance suite has jumped to the left, and my forecast has followed suit, fairly close to the latest TVCN/TVCE model consensus forecasts. The model guidance is unanimous in showing Arthur making a landfall in Nova Scotia on Saturday morning, likely as a gradually winding down extatropical cyclone. However, Arthur will likely still contain winds in the 45 to 50 kt range as it makes landfall there, and residents there should anticipate the possibility of tree and power line damage. For this reason, a tropical storm watch has been issued for all of the coast of Nova Scotia by the National Hurricane Center. Some deceleration is forecast at the end of the forecast period as the hurricane orbits around a larger extratropical cyclone over the north Atlantic.

So far, the highest reported sustained winds from land stations were 77 mph gusting to 101 mph at Cape Lookout a few hours ago. In addition, Okracoke Island reported a wind gust to 99 mph, also reported several hours ago. Doppler radar indicates that the eyewall and strongest winds are over northern Dare County in far eastern North Carolina. As Arthur pulls away, winds will shift around to the west and gradually diminish.

A tornado watch remains in effect for eastern North Carolina and adjacent coastal waters until 8:00 AM local time as per the Storm Prediction Center. There has so far been one tornado report, occurring at Rose Hill in Duplin County; this is located in central North Carolina at a location that's well inland. The evening hodograph at Morehead City wasn't the most favorable I've seen, although there could be enough curvature to generate a couple more tornadoes along immediate coastal areas experiencing the northern eyewall or the rainbands emanting north from the center, but with Arthur's right-front quadrant just offshore, the overall tornado threat appears to be marginal.

Heavy rainfall has already fallen, with doppler radar estimates of 2 to 5 inches across much of southern and eastern North Carolina. This is not surprising since the northern portion of Arthur is already interacting with an approaching cold front.

Storm surge flooding should slowly subside after Arthur completely moves away from the coast. Much of the coast is already experiencing offshore flow as the eye steadily moves away.

Residents still under the hurricane warning area should not venture outside. Even though Arthur is quickly pulling away from the coast as it gets captured by the trough, strong and damaging winds will linger for several more hours. Interests in Cape Cod should also monitor the hurricane as it accelerates northeast; a tropical storm warning has been issued there as well.

Of note, Arthur is the strongest hurricane to make landfall on the mainland United States since Hurricane Ike of 2008. It is also the earliest hurricane landfall for North Carolina.

Intensity forecast

Initial 07/04 0700Z 35,6°N 75.9°W 85 kt 100 mph: inland
12 hour 07/04 1800Z 37.6°N 73.5°W 90 kt 105 mph
24 hour 07/05 0600Z 41.3°N 69.6°W 75 kt 85 mph
36 hour 07/05 1800Z 44.1°N 65.9°W 60 kt 70 mph: extratropical
48 hour 07/06 0600Z 47.1°N 61.1°W 50 kt 60 mph: extratropical

Track forecast



Figure 2. My forecast track for Arthur.

NHC storm information


000
WTNT31 KNHC 040659
TCPAT1

BULLETIN
HURRICANE ARTHUR INTERMEDIATE ADVISORY NUMBER 13B
NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014
300 AM EDT FRI JUL 04 2014

...EYE OF ARTHUR MOVING NEAR MAINLAND DARE COUNTY AND NORTHERN
PAMLICO SOUND...
...HURRICANE CONDITIONS SPREADING NORTHWARD ALONG THE OUTER BANKS...


SUMMARY OF 300 AM EDT...0700 UTC...INFORMATION
----------------------------------------------
LOCATION...35.6N 75.9W
ABOUT 25 MI...40 KM SSW OF MANTEO NORTH CAROLINA
ABOUT 35 MI...55 KM NW OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...100 MPH...155 KM/H
PRESENT MOVEMENT...NE OR 40 DEGREES AT 22 MPH...35 KM/H
MINIMUM CENTRAL PRESSURE...973 MB...28.73 INCHES


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

THE HURRICANE WARNING FROM SOUTH OF BOGUE INLET NORTH CAROLINA HAS
BEEN DISCONTINUED.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* BOGUE INLET NORTH CAROLINA TO THE NORTH CAROLINA/VIRGINIA BORDER
* PAMLICO SOUND
* EASTERN ALBEMARLE SOUND

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* THE NORTH CAROLINA/VIRGINIA BORDER TO CAPE CHARLES LIGHT
VIRGINIA...INCLUDING THE MOUTH OF THE CHESAPEAKE BAY
* WESTERN ALBEMARLE SOUND
* NANTUCKET
* CAPE COD FROM PROVINCETOWN TO CHATHAM

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* NEW BRUNSWICK FROM THE U. S./CANADA BORDER TO GRAND-ANSE
* ALL OF NOVA SCOTIA INCLUDING CAPE BRETON ISLAND
* ALL OF PRINCE EDWARD ISLAND

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE
AND PROPERTY SHOULD HAVE ALREADY BEEN COMPLETED.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA.

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

INTERESTS ELSEWHERE IN COASTAL PORTIONS OF NEW ENGLAND...NEW
BRUNSWICK...AND NEWFOUNDLAND SHOULD MONITOR THE PROGRESS OF ARTHUR.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA IN THE UNITED
STATES...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS...PLEASE
MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE
FORECAST OFFICE. FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE
THE UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 300 AM EDT...0700 UTC...THE EYE OF HURRICANE ARTHUR WAS LOCATED
BY NOAA DOPPLER RADAR NEAR LATITUDE 35.6 NORTH...LONGITUDE 75.9
WEST. ARTHUR IS MOVING TOWARD THE NORTHEAST NEAR 22 MPH...35
KM/H...AND THIS MOTION IS EXPECTED TO CONTINUE WITH AN INCREASE IN
FORWARD SPEED DURING THE NEXT COUPLE OF DAYS. ON THE FORECAST
TRACK...THE CENTER OF ARTHUR WILL MOVE OVER THE NORTHERN OUTER
BANKS AND THEN MOVE OFFSHORE DURING THE NEXT FEW HOURS. ARTHUR WILL
PASS SOUTHEAST OF NEW ENGLAND LATER TODAY OR TONIGHT...AND BE NEAR
OR OVER WESTERN NOVA SCOTIA EARLY SATURDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 100 MPH...155 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IN STRENGTH IS EXPECTED DURING THE NEXT FEW
HOURS. HOWEVER...ARTHUR IS EXPECTED TO BEGIN WEAKENING LATER TODAY
AND BECOME A POST-TROPICAL CYCLONE TONIGHT OR SATURDAY.

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 40 MILES...65 KM...FROM
THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 150
MILES...240 KM. A WEATHERFLOW STATION LOCATED NEAR AVON RECENTLY
REPORTED A SUSTAINED WIND OF 73 MPH...117 KM/H...AND A WIND GUST OF
84 MPH...135 KM/H. A U.S. COAST GUARD STATION JUST WEST OF CAPE
HATTERAS RECENTLY REPORTED A WIND GUST OF 89 MPH...145 KM/H.

THE MINIMUM CENTRAL PRESSURE BASED ON DATA FROM AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT IS 973 MB...28.73 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS WILL CONTINUE SPREADING INTO
PORTIONS OF THE TROPICAL STORM WARNING AREA IN VIRGINIA THIS
MORNING. HURRICANE CONDITIONS WILL CONTINUE SPREADING NORTHWARD
THROUGH PORTIONS OF THE HURRICANE WARNING AREA DURING THE NEXT FEW
HOURS. TROPICAL STORM CONDITIONS ARE EXPECTED TO REACH THE NEW
ENGLAND WARNING AREA BY TONIGHT.

STORM SURGE...THE COMBINATION OF A DANGEROUS 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...

NORTH CAROLINA WITHIN THE HURRICANE WARNING AREA...3 TO 5 FT
PAMLICO AND ALBEMARLE SOUNDS...2 TO 4 FT
SOUTHERN NORTH CAROLINA WITHIN THE TROPICAL STORM WARNING AREA...1
TO 3 FT
EXTREME SOUTHEASTERN VIRGINIA...1 TO 3 FT

COASTAL FLOODING IS ALSO POSSIBLE ALONG CAPE COD.

THE HIGHEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST IN AREAS OF
ONSHORE FLOW. THE SURGE WILL BE ACCOMPANIED BY LARGE AND DAMAGING
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 AND
THE NEW EXPERIMENTAL POTENTIAL STORM SURGE FLOODING MAP FOR MORE
DETAILS.

RAINFALL...RAINFALL ACCUMULATIONS OF 4 TO 6 INCHES...WITH ISOLATED
MAXIMUM AMOUNTS OF 8 INCHES...ARE EXPECTED OVER COASTAL AREAS OF
NORTH CAROLINA THROUGH TODAY. RAINFALL ACCUMULATIONS OF 2 TO 4
INCHES ARE EXPECTED OVER PORTIONS OF EASTERN MASSACHUSETTS AND RHODE
ISLAND.

TORNADOES...ISOLATED TORNADOES ARE POSSIBLE OVER PORTIONS OF
COASTAL NORTH CAROLINA AND SOUTHEASTERN VIRGINIA THROUGH THIS
MORNING.

SURF...SWELLS GENERATED BY ARTHUR ARE AFFECTING AREAS ALONG THE
COAST OF NORTH CAROLINA. THESE SWELLS ARE EXPECTED TO CAUSE
LIFE-THREATENING SURF AND RIP CURRENTS. FOR MORE INFORMATION...
PLEASE MONITOR PRODUCTS ISSUED BY YOUR LOCAL NATIONAL WEATHER
SERVICE FORECAST OFFICE.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...500 AM EDT.

$$
FORECASTER BRENNAN/LANDSEA

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3. WunderAlertBot (Admin)
7:42 AM GMT on July 05, 2014
KoritheMan has created a new entry.
2. skycycle
8:31 AM GMT on July 04, 2014
Thanks for the update, nice read :)
Member Since: August 26, 2009 Posts: 0 Comments: 208
1. Wolfberry
7:58 AM GMT on July 04, 2014
Thanks Kori great work..
Member Since: April 1, 2014 Posts: 0 Comments: 212

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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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