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98L may develop early next week

By: Dr. Jeff Masters, 2:13 PM GMT on October 10, 2012

A tropical wave located about 500 miles east of the Lesser Antilles Islands (Invest 98L) is headed west-northwest at about 15 mph, and is a threat to develop into a tropical depression early next week. The disturbance has a modest amount of spin and a large amount of disorganized heavy thunderstorms, as seen on satellite loops, but there is no sign of a surface circulation. Wind shear is a moderate 10 - 20 knots over 98L, the atmosphere is moist, and ocean temperatures are a very warm 30°C. With wind shear expected to rise to the high range, 20 - 30 knots, Wednesday night though Friday, any development the next few days should be slow. The shear is due to an upper-level trough of low pressure centered a few hundred miles northeast of the Lesser Antilles Islands. Once 98L passes beyond the Lesser Antilles on Saturday, the shearing winds of the trough will diminish to the moderate range, 10 - 20 knots. Most of the models predict that 98L will show increasing development beginning on Saturday. The NOGAPS model has 98L developing into a tropical depression on Monday, a few hundred miles northeast of the southeastern Bahama Islands. The GFS model is much slower with the system, predicting it will develop into a tropical depression on Monday, a few hundred miles north of Puerto Rico. Moisture from 98L should affect the Lesser Antilles Islands on Thursday and Friday, and Puerto Rico and the Virgin Islands on Friday and Saturday. It is uncertain if heavy rains from 98L will affect the Dominican Republic early next week; the storm may stay too far to the northeast. In their 8 am Tropical Weather Outlook, NHC gave 98L a 30% chance of becoming a tropical cyclone by Friday morning. The long range fate of 98L is uncertain; the ECMWF model shows 98L becoming absorbed by a cold front and bringing heavy rains to Canada and New England on Tuesday and Wednesday next week, while the GFS and NOGAPS models predict that 98L will stay out to sea for at least the next week.


Figure 1. Morning satellite image of Invest 98L approaching the Lesser Antilles Islands.

Jeff Masters

Hurricane

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Good Morning!

Henry Margusity Fan Club
To top it off, we may have another major severe weather outbreak next week just east of where it happens Saturday.
98L...

Quoting TomballTXPride:

Where does it specifically say the SPC is considering an upgrade to a moderate risk, Cody?

It is strongly implied.

"GIVEN THE STRENGTH OF THE WARM SECTOR DEEP LAYER MEAN FLOW
FIELDS/SHEAR AND FORCING FOR UPWARD VERTICAL MOTION...SEVERE
POTENTIAL ON SATURDAY MAY ULTIMATELY BE HIGHER THAN CURRENTLY
INDICATED BY THE SLIGHT RISK CATEGORICAL OUTLOOK."
NHC remains consistantly inconsistant when it comes to designating systems....same as it ever was.
505. SLU
Man, the NHC wins the award for the world's most conservative meteorological organisation.

000
ABNT20 KNHC 111133
TWOAT

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT THU OCT 11 2012

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
LOCATED ABOUT 350 MILES EAST-SOUTHEAST OF THE WINDWARD ISLANDS.
SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED A LITTLE NEAR THE
LOW DURING THE LAST FEW HOURS...AND ENVIRONMENTAL CONDITIONS APPEAR
CONDUCIVE FOR GRADUAL DEVELOPMENT OF THIS LARGE DISTURBANCE OVER
THE NEXT COUPLE OF DAYS. THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES WEST-NORTHWESTWARD AT 10 TO 15 MPH. REGARDLESS OF
DEVELOPMENT...STRONG GUSTY WINDS AND HEAVY RAINFALL ARE POSSIBLE
ACROSS PORTIONS OF THE LESSER ANTILLES DURING THE NEXT COUPLE OF
DAYS. ADDITIONAL INFORMATION ON THIS DISTURBANCE CAN BE FOUND IN
HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WATHER SERVICE.

SHOWER AND THUNDERSTORM ACTIVITY HAS CHANGED LITTLE OVER THE PAST
FEW HOURS IN ASSOCIATION WITH A SMALL AREA OF LOW PRESSURE LOCATED
ABOUT 250 MILES NORTHEAST OF THE CENTRAL BAHAMAS. THERE IS STILL A
SMALL WINDOW OF OPPORTUNITY FOR A TROPICAL DEPRESSION TO FORM
BEFORE THE LOW MERGES WITH A COLD FRONT LATER TODAY. THIS SYSTEM
HAS A MEDIUM CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES SLOWLY SOUTHWARD. ADDITIONAL
INFORMATION ON THIS DISTURBANCE CAN BE FOUND IN HIGH SEAS FORECASTS
ISSUED BY THE NATIONAL WATHER SERVICE.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.
Quoting TropicalAnalystwx13:

It is strongly implied.

"GIVEN THE STRENGTH OF THE WARM SECTOR DEEP LAYER MEAN FLOW
FIELDS/SHEAR AND FORCING FOR UPWARD VERTICAL MOTION...SEVERE
POTENTIAL ON SATURDAY MAY ULTIMATELY BE HIGHER THAN CURRENTLY
INDICATED BY THE SLIGHT RISK CATEGORICAL OUTLOOK."

That doesn't necessarily imply a moderate risk though. That could be including more areas in a upgrade to 30%, which is still in the slight risk category. That could also mean upping the percentages for winds, hail, and tornado potentials on the subsequent SVR T-Storm/Tornado watches that may be issued as needed. That could also mean including a hatched area of winds greater that 65 knots or hail greater than 2" for any convective outlook issued that day. However, that does not necessarily mean upgrading to a moderate risk.
Quoting TomballTXPride:

That doesn't necessarily imply a moderate risk though. That could be including more areas in a upgrade to 30%, which is still in the slight risk category.

It is implying that an upgrade to a MDT risk is possible but not 100% likely. At least that is how I viewed it.
Quoting wxchaser97:

It is implying that an upgrade to a MDT risk is possible but not 100% likely.

Not necessarily. I don't see that wording in there at all.
Quoting PensacolaDoug:
NHC remains consistantly inconsistant when it comes to designating systems....same as it ever was.

Well they did name Oscar and that was a stretch. Invest 97L is likely a depression and should/hopefully be classified at 11am.
The NHC is not going to waste a name or a number (lol)....they think the storm is not going to last long.... BUT that should not matter.
Why are they doing this?

WHY YOU DON'T ISSUE ADVISORIES???? Who has that pic by the way?
Quoting TomballTXPride:

Not necessarily. I don't see that wording in there at all.

Well if the severe risk is possibly higher than a slight risk, which is what they're saying, then it would be upgraded to a MDT risk.
JeffMasters has created a new entry.
Quoting TomballTXPride:

That doesn't necessarily imply a moderate risk though. That could be including more areas in a upgrade to 30%, which is still in the slight risk category. That could also mean upping the percentages for winds, hail, and tornado potentials on the subsequent SVR T-Storm/Tornado watches that may be issued as needed. That could also mean including a hatched area of winds greater that 65 knots or hail greater than 2" for any convective outlook issued that day. However, that does not necessarily mean upgrading to a moderate risk.

It could. However, considering Kerr wrote it, I wouldn't bet on it.

Forecaster Kerr = SPC's Forecast Stewart.
I completely agree. The Bahama blob is amazingly persistent and is worth a stronger designation.
This looks like a potent system,and all the models are pickin it up.