Forecast: “Major” Hurricane Irene; MN: Overnight Thunder?

Hurricane Irene is gathering steam and ready to roll.

All systems appear to be “go” for Irene, the Atlantic season’s first hurricane, to morph & mutate into the first major hurricane of 2011.

Current Conditions:

Irene beat up on Puerto Rico Sunday & early Monday. By late Monday Hurricane Irene is a Category 1 hurricane on the Saffir- Simpson Hurricane Intensity Scale with 80 mph winds.

BULLETIN

HURRICANE IRENE ADVISORY NUMBER 9

NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011

500 PM AST MON AUG 22 2011

…IRENE AIMS AT THE BAHAMAS…FORECAST TO BECOME A STRONG

HURRICANE…

SUMMARY OF 500 PM AST…2100 UTC…INFORMATION

———————————————-

LOCATION…19.5N 68.6W

ABOUT 215 MI…340 KM SE OF GRAND TURK ISLAND

ABOUT 65 MI…100 KM NNW OF PUNTA CANA DOMINICAN REPUBLIC

MAXIMUM SUSTAINED WINDS…80 MPH…130 KM/H

PRESENT MOVEMENT…WNW OR 295 DEGREES AT 13 MPH…20 KM/H

MINIMUM CENTRAL PRESSURE…988 MB…29.18 INCHES

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Visible satellite image shows Irene growing north of Hispaniola.

(Click to enalrge for easily readable images)

Track Forecast:

All the various computer model tracks agree on two things during the next 48 hours.

1) Irene is headed for the Bahamas.

2) Irene is going track over mostly warm, open waters and grow stronger.

The “official” NHC track takes Irene toward the South Carolina coast Saturday as a major hurricane.

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After 48 hours larger differences in tracks emerge, but the consensus is that Irene will recurve northward and may either make landfall in the USA or parallel the coast for a while.

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Keep in mind that the 5 year average error for hurricane track forecasts is about 200 miles 4 days out.

The latest model packages have shown a general trend to shift the track slightly east.

This may be good news for south Florida, if Irene is able to track further offshore.

This may also increase the chances of a direct hit on the Carolinas, and more time over open ocean and a warm Gulf Stream may cause Irene to intensify and explode into a major hurricane.

Intensity Forecast:

Irene’s probable track over warm open waters and the super warm Gulf Stream current look favorable for turning Irene into a large, well organized major (Category 3 or higher) hurricane in the next 72 hours.

From the NHC discussion….

“ALL OF THE INGREDIENTS ARE CONDUCIVE FOR IRENE TO INTENSIFY OVER THE NEXT FEW DAYS. THE OFFICIAL FORECAST CALLS FOR IRENE TO BECOME A STRONG CATEGORY 2 OR CATEGORY 3 HURRICANE ON THE SAFFIR-SIMPSON HURRICANE WIND SCALE AS IRENE MOVES ACROSS THE CENTRAL AND NORTHWESTERN BAHAMAS. IN FACT…BOTH THE GFS AND THE ECMWF GLOBAL MODELS INSIST ON MAKING IRENE A LARGE AND STRONG HURRICANE WITH MINIMUM PRESSURES AROUND 945 MB AND 952 MB…RESPECTIVELY.”

Official NHC intensity forecast surges Irene to 115 mph by Thursday, a major Category 3 storm. The GFS model, (which appears to have successfully predicted the notion of development and approximate location of Irene somewhere off the Florida coast 10 days in advance!) drops Irene’s central pressure to 945 millibars, which would make Irene a borderline Category 4 Hurricane!

FORECAST POSITIONS AND MAX WINDS

INIT 22/2100Z 19.5N 68.6W 70 KT 80 MPH

12H 23/0600Z 20.1N 70.2W 80 KT 90 MPH

24H 23/1800Z 20.8N 72.5W 85 KT 100 MPH

36H 24/0600Z 21.5N 74.0W 90 KT 105 MPH

48H 24/1800Z 23.0N 75.5W 95 KT 110 MPH

72H 25/1800Z 26.0N 78.0W 100 KT 115 MPH

96H 26/1800Z 29.5N 79.0W 100 KT 115 MPH

120H 27/1800Z 34.0N 79.0W 80 KT 90 MPH…INLAND

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Either way, all indications are that Irene is going to be a nasty major hurricane by Thursday. Irene could reach Category 3, or possible Category 4 intensity by then.

Keep in mind that hurricane track forecasts are generally more accurate and reliable than hurricane intensity forecasts. If Irene encounters favorable (low) wind shear over the super warm Gulf Stream current off the Florida Coast, she may get a “super charged” shot of energy and undergo rapid intensification Thursday.

USA Threats?

South Florida may be breathing slightly easier today with the eastward shift of the model consensus, but Florida is not out of the woods yet for several reasons.

-The NAM model still predicts a direct hit near Miami late Thursday night or Friday morning.

-Irene will grow in size and intensity, and even if the center tracks 100+ miles offshore, the storm may be large enough and powerful enough to do damage on Florida’s east coast, especially in northern Florida near Jacksonville.

The official NHC track, and the model consensus puts the Carolinas most at risk for a direct strike from a major Category 3 hurricane Saturday.

After that there are also scary scenarios for Washington D.C., New York City and Long Island, and even Boston and Cape Cod.

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Stay tuned for the latest track and intensity shifts. The next 48 hours will be critical in telling just how strong Irene will get, and where she may strike!

Minnesota Forecast: Possible MCS overnight & early Tuesday?

It could get loud & wet in parts of Minnesota overnight & early Tuesday.

A hot, sticky tropical air mass may greet Minnesotans with some heavy thunderstorms and a possible MCS overnight into Tuesday morning. Call it a “sunrise surprise” in some areas, but be ready for some potentially big storms to fire in the overnight hours and rumble through early Tuesday morning.

The storms have the potential to pack high winds, hail and heavy rainfall.

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NAM model paints some .50″ to 1″+ rainfall totals near the metro Tuesday morning.

SPC has placed much of Minnesota under a slight risk for severe weather.

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Don’t be “sunrise surprised” if you get shook out of bed by a loud crack of thunder early Tuesday morning!

PH

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