TD 2 struggling; new African wave bears watching
Tropical Depression Two is struggling. The depression still has a good chance of becoming the Atlantic hurricane season's first named storm this week, but the dry, Saharan air that surrounds the storm, combined with moderately high levels of wind shear, are interfering with the storm's organization. Satellite loops of the storm show that heavy thunderstorm activity is limited to the west side of the depression. This is due to strong winds out of the southeast that are creating a moderate 15 - 20 knots of wind shear. The intensity and coverage of these thunderstorms is meager, thanks to the large amount of dry air to TD 2's north that is getting wrapped into the circulation. This morning's QuikSCAT pass showed a well-formed surface circulation, with top winds of about 30 - 35 mph.
Wind shear over TD 2 is expected to remain in the moderate range, 10 - 20 knots, over the next five days. Sea Surface Temperatures (SSTs) are a marginal 26 - 27°C, and will not change much over the next three days. There is plenty of dry, stable air from the Saharan Air Layer (SAL) to to TD 2's north that will continue to cause the storm problems. The relatively cool SSTs and dry air mean that TD 2 will not be able to intensify quickly. However, it does appear likely that TD 2 has enough going for it that it will eventually be able to become Tropical Storm Ana sometime in the next three days. Most of the computer models show some weak development, but none of them predict TD 2 will become a hurricane. It is unusual for storms forming this far north to make it all the way across the Atlantic to hit the Lesser Antilles Islands. For now, TD 2 doesn't concern me as much as the new tropical wave to its southeast, just off the coast of Africa.
Figure 1. Tropical Depression Two (left center of image) and a new tropical wave (right side of image), newly emerged from the coast of Africa.
Elsewhere in the Atlantic
A strong tropical wave with some rotation and plenty of heavy thunderstorm activity left the coast of Africa yesterday, and is located a few hundred miles south of the Cape Verdes Islands. The GFS and ECMWF models continue to predict the development of this wave late this week. Both of these models indicate that the wave would track further south than Tropical Depression Two, and could impact the Lesser Antilles Islands in about seven days. This storm bears close attention over the coming days.
Two other tropical waves, one that just passed through the Lesser Antilles Islands, and one about 300 miles east of the islands, are mentioned in NHC's Graphical Tropical Weather Outlook. Both of these waves have very limited heavy thunderstorm activity that is not increasing, and are not a threat to develop over the next two days. None of the computer models develop either of these waves.
Felicia moves through Hawaiian Islands as a tropical depression
Tropical Storm Felicia weakened to a tropical depression before passing through the Hawaiian Islands yesterday. The storm brought scattered heavy rains of 1 - 2 inches to the islands, and no damage was reported. Felicia is only the 10th tropical cyclone of tropical depression strength or higher to hit the islands since 1950. Four other tropical cyclones have passed within 75 miles of the islands during that time period.
Be careful clicking on external links in blog comments
A comment may have been posted on my blog over the weekend containing links to a malicious web site that infected some people's computers when they clicked on the link. The exact link responsible has eluded us thus far, and we are also investigating the possibility that a bad banner ad was responsible. To provide an extra layer of protection, we've installed software on the blogs that will now warn users that they are leaving the site when they click on an external link, so that one has do an extra click to go to an external site. This will give users an opportunity to think twice before clicking on a potentially dangerous link. I apologize to anybody who may have been affected by the attack. Please submit a support ticket to help us out in the future for any issues of this nature.
I'll have an update Thursday morning.
Jeff Masters
Reader Comments
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Seriously? People are just having fun with it.
Fixing to storm here.
anA?
If TD2 had just maintained its appearance, I'm sure the NHC would have named at 5PM in deference to the different agencies + the ADT all showing 2.5 for different points during the morning.
However, once the CoC was exposed AND the convection started dying they had to change their mind or look foolish.
LMAO
"Alpha Dog 1"
What would have been the point in classifying it a TS only to downgrade it again at the next update ?.
Not even close.
Ya, they never did change the name in any of the databases, they had it as TWO TS.
WTNT32 KNHC 122033
TCPAT2
BULLETIN
TROPICAL DEPRESSION TWO ADVISORY NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
500 PM AST WED AUG 12 2009
...DEPRESSION HAS NOT YET BECOME A TROPICAL STORM...
AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION TWO WAS
LOCATED NEAR LATITUDE 14.3 NORTH...LONGITUDE 35.0 WEST OR ABOUT 710
MILES...1140 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.
THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 14 MPH...23 KM/HR. A
GENERAL MOTION TOWARD THE WEST IS EXPECTED TO CONTINUE FOR THE NEXT
48 HOURS.
MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. SLOW STRENGTHENING IS POSSIBLE...AND THE DEPRESSION COULD
BECOME A TROPICAL STORM DURING THE NEXT DAY OR TWO.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB...29.71 INCHES.
...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...14.3N 35.0W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 265 DEGREES AT 14 MPH
MINIMUM CENTRAL PRESSURE...1006 MB
THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.
$$
FORECASTER BEVEN
Too funny.
Hey, what about me! Getting hammered in FWB too!
WTNT32 KNHC 122033
TCPAT2
BULLETIN
TROPICAL DEPRESSION TWO ADVISORY NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
500 PM AST WED AUG 12 2009
...DEPRESSION HAS NOT YET BECOME A TROPICAL STORM...
AT 500 PM AST...2100 UTC...THE CENTER OF TROPICAL DEPRESSION TWO WAS
LOCATED NEAR LATITUDE 14.3 NORTH...LONGITUDE 35.0 WEST OR ABOUT 710
MILES...1140 KM...WEST OF THE SOUTHERNMOST CAPE VERDE ISLANDS.
THE DEPRESSION IS MOVING TOWARD THE WEST NEAR 14 MPH...23 KM/HR. A
GENERAL MOTION TOWARD THE WEST IS EXPECTED TO CONTINUE FOR THE NEXT
48 HOURS.
MAXIMUM SUSTAINED WINDS ARE NEAR 35 MPH...55 KM/HR...WITH HIGHER
GUSTS. SLOW STRENGTHENING IS POSSIBLE...AND THE DEPRESSION COULD
BECOME A TROPICAL STORM DURING THE NEXT DAY OR TWO.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB...29.71 INCHES.
...SUMMARY OF 500 PM AST INFORMATION...
LOCATION...14.3N 35.0W
MAXIMUM SUSTAINED WINDS...35 MPH
PRESENT MOVEMENT...WEST OR 265 DEGREES AT 14 MPH
MINIMUM CENTRAL PRESSURE...1006 MB
THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER AT
1100 PM AST.
$$
FORECASTER BEVEN
WTNT42 KNHC 122034
TCDAT2
TROPICAL DEPRESSION TWO DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
500 PM AST WED AUG 12 2009
THE DEPRESSION APPEARED TO BE ON THE VERGE OF BECOMING A TROPICAL
STORM A FEW HOURS AGO...WITH SATELLITE INTENSITY ESTIMATES OF 35 KT
FROM TAFB AND SAB. HOWEVER...SINCE ABOUT 18Z THE CONVECTION HAS
DECREASED SIGNIFICANTLY AND HAS MOVED FARTHER AWAY FROM THE EXPOSED
LOW-LEVEL CENTER. BASED ON THIS...THE CYCLONE WILL REMAIN A 30 KT
DEPRESSION FOR THIS ADVISORY. THE CURRENT DOWNWARD TREND IN THE
CONVECTION MAY BE DUE TO AN INCREASE IN EASTERLY VERTICAL WIND
SHEAR...AND TO A DRY SLOT WRAPPING AROUND THE CIRCULATION NOTED IN
AMSR-E VAPOR IMAGERY NEAR 1534Z. ALSO...AS SEEN EARLIER...MOST OF
THE LOW-LEVEL INFLOW INTO THE DEPRESSION SEEMS TO BE COMING FROM
THE NORTH...REPRESENTING POSSIBLY MORE STABLE AIR PASSING OVER
COOLER WATERS. THE FLOW ON THE SOUTH SIDE OF THE DEPRESSION IS
FEEDING INTO A LARGE DISTURBANCE BETWEEN THE CAPE VERDE ISLANDS AND
AFRICA.
THE INITIAL MOTION IS 265/12. THE DEPRESSION IS ON THE SOUTH
SIDE OF A LARGE LOW/MID-LEVEL RIDGE...AND THE LARGE-SCALE MODELS
FORECAST THIS TO CONTINUE FOR THE NEXT TWO DAYS OR SO. AFTER THAT
TIME...THE MODELS FORECAST A WEAKNESS IN THE RIDGE THAT WOULD STEER
THE CYCLONE WEST-NORTHWESTWARD. THE TRACK MODEL GUIDANCE GENERALLY
AGREES WITH THIS SCENARIO...AND WHILE THE MODEL CLUSTERS SEEN
EARLIER HAVE MERGED THERE IS STILL A SIGNIFICANT SPREAD BY 120 HR.
THE GFS AND UKMET ARE ON THE SOUTH SIDE OF THE GUIDANCE ENVELOPE
SHOWING A MORE WESTERLY MOTION...WHILE THE HWRF AND BAMD ARE ON THE
NORTH SIDE SHOWING A NORTHWESTWARD MOTION BY 120 HR. OVERALL...THE
GUIDANCE ENVELOPE HAS AGAIN SHIFTED A LITTLE SOUTHWARD...AND SO HAS
THE NEW OFFICIAL FORECAST. THE NEW TRACK IS IN THE CENTER OF THE
GUIDANCE ENVELOPE IN BEST AGREEMENT WITH THE TVCN AND TVCC
CONSENSUS MODELS.
THE DEPRESSION REMAINS OVER SEA SURFACE TEMPERATURES NEAR 27C...WITH
SSTS ALONG THE FORECAST TRACK INCREASING TO 28C AFTER 72 HR. THE
LARGE-SCALE MODELS FORECAST THE DEPRESSION TO ENCOUNTER MODERATE
VERTICAL WIND SHEAR DURING THE FORECAST PERIOD...FIRST FROM THE
EAST AND LATER FROM THE SOUTHWEST. ALSO...WATER VAPOR IMAGERY
SHOWS VERY DRY AIR AT THE MID/UPPER-LEVELS TO THE NORTHWEST OF THE
DEPRESSION. THE LATTER TWO FACTORS SUGGEST THE SYSTEM MAY BE SLOW
TO STRENGTHEN...AND NONE OF THE INTENSITY GUIDANCE CURRENTLY
FORECASTS AN INTENSITY GREATER THAN 55 KT DURING THE FORECAST
PERIOD. BASED ON THIS...THE NEW INTENSITY FORECAST IS AN UPDATE OF
THE PREVIOUS FORECAST IN BEST AGREEMENT WITH THE SHIPS MODEL. IT
IS POSSIBLE THAT THE SYSTEM COULD WEAKEN TO A TROPICAL WAVE DURING
THE FORECAST PERIOD...AS FORECAST BY THE ECMWF...UKMET...AND GFS
MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 12/2100Z 14.3N 35.0W 30 KT
12HR VT 13/0600Z 14.1N 36.7W 35 KT
24HR VT 13/1800Z 14.1N 38.9W 35 KT
36HR VT 14/0600Z 14.2N 41.3W 40 KT
48HR VT 14/1800Z 14.6N 43.7W 45 KT
72HR VT 15/1800Z 16.0N 49.5W 50 KT
96HR VT 16/1800Z 19.0N 56.0W 50 KT
120HR VT 17/1800Z 23.0N 62.0W 45 KT
$$
FORECASTER BEVEN
I meant probably isn't as worse.
they probably feel like "when i need group therapy i just go for a ride alone in my car"
Oh OK, I was going to say your comments were G or PG-13 at worst!
They were going to name it but they changed their minds when Ana got really ragged in the last hour or two.
My CPR efforts are blowing her in that direction
..she will get there,and Become Ana,..but she's
going to have to travel a lil more west to a Lower Shear environment before that will occur.
MAYBE it will get named at 5 AM tomorrow.
They won't name it at 11, they're to conservative for that.
STORM A FEW HOURS AGO...WITH SATELLITE INTENSITY ESTIMATES OF 35 KT
FROM TAFB AND SAB. HOWEVER...SINCE ABOUT 18Z THE CONVECTION HAS
DECREASED SIGNIFICANTLY AND HAS MOVED FARTHER AWAY FROM THE EXPOSED
LOW-LEVEL CENTER. BASED ON THIS...THE CYCLONE WILL REMAIN A 30 KT
DEPRESSION FOR THIS ADVISORY.
Ok, so they were going to name it, wasn't an error, but TD2 just screwed her big opportunity!
Unless hes on vacation...
MAYBE it will get named at 5 AM tomorrow.
They won't name it at 11, they're to conservative for that.
Does anyone have an opinion on whether this makes the storm more viable?
WTNT42 KNHC 122034
TCDAT2
TROPICAL DEPRESSION TWO DISCUSSION NUMBER 7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL022009
500 PM AST WED AUG 12 2009
THE DEPRESSION APPEARED TO BE ON THE VERGE OF BECOMING A TROPICAL
STORM A FEW HOURS AGO...WITH SATELLITE INTENSITY ESTIMATES OF 35 KT
FROM TAFB AND SAB. HOWEVER...SINCE ABOUT 18Z THE CONVECTION HAS
DECREASED SIGNIFICANTLY AND HAS MOVED FARTHER AWAY FROM THE EXPOSED
LOW-LEVEL CENTER. BASED ON THIS...THE CYCLONE WILL REMAIN A 30 KT
DEPRESSION FOR THIS ADVISORY (Aw come on... TSs are based on winds, not looks). THE CURRENT DOWNWARD TREND IN THE
CONVECTION MAY BE DUE TO AN INCREASE IN EASTERLY VERTICAL WIND
SHEAR...AND TO A DRY SLOT WRAPPING AROUND THE CIRCULATION NOTED IN
AMSR-E VAPOR IMAGERY NEAR 1534Z. ALSO...AS SEEN EARLIER...MOST OF
THE LOW-LEVEL INFLOW INTO THE DEPRESSION SEEMS TO BE COMING FROM
THE NORTH...REPRESENTING POSSIBLY MORE STABLE AIR PASSING OVER
COOLER WATERS. THE FLOW ON THE SOUTH SIDE OF THE DEPRESSION IS
FEEDING INTO A LARGE DISTURBANCE BETWEEN THE CAPE VERDE ISLANDS AND
AFRICA (still flowing into the Bill/Ana wave).
THE INITIAL MOTION IS 265/12. THE DEPRESSION IS ON THE SOUTH
SIDE OF A LARGE LOW/MID-LEVEL RIDGE...AND THE LARGE-SCALE MODELS
FORECAST THIS TO CONTINUE FOR THE NEXT TWO DAYS OR SO. AFTER THAT
TIME...THE MODELS FORECAST A WEAKNESS IN THE RIDGE THAT WOULD STEER
THE CYCLONE WEST-NORTHWESTWARD. THE TRACK MODEL GUIDANCE GENERALLY
AGREES WITH THIS SCENARIO...AND WHILE THE MODEL CLUSTERS SEEN
EARLIER HAVE MERGED THERE IS STILL A SIGNIFICANT SPREAD BY 120 HR.
THE GFS AND UKMET ARE ON THE SOUTH SIDE OF THE GUIDANCE ENVELOPE
SHOWING A MORE WESTERLY MOTION...WHILE THE HWRF AND BAMD ARE ON THE
NORTH SIDE SHOWING A NORTHWESTWARD MOTION BY 120 HR. OVERALL...THE
GUIDANCE ENVELOPE HAS AGAIN SHIFTED A LITTLE SOUTHWARD...AND SO HAS
THE NEW OFFICIAL FORECAST. THE NEW TRACK IS IN THE CENTER OF THE
GUIDANCE ENVELOPE IN BEST AGREEMENT WITH THE TVCN AND TVCC
CONSENSUS MODELS.
THE DEPRESSION REMAINS OVER SEA SURFACE TEMPERATURES NEAR 27C...WITH
SSTS ALONG THE FORECAST TRACK INCREASING TO 28C AFTER 72 HR. THE
LARGE-SCALE MODELS FORECAST THE DEPRESSION TO ENCOUNTER MODERATE
VERTICAL WIND SHEAR DURING THE FORECAST PERIOD...FIRST FROM THE
EAST AND LATER FROM THE SOUTHWEST. ALSO...WATER VAPOR IMAGERY
SHOWS VERY DRY AIR AT THE MID/UPPER-LEVELS TO THE NORTHWEST OF THE
DEPRESSION. THE LATTER TWO FACTORS SUGGEST THE SYSTEM MAY BE SLOW
TO STRENGTHEN...AND NONE OF THE INTENSITY GUIDANCE CURRENTLY
FORECASTS AN INTENSITY GREATER THAN 55 KT DURING THE FORECAST
PERIOD. BASED ON THIS...THE NEW INTENSITY FORECAST IS AN UPDATE OF
THE PREVIOUS FORECAST IN BEST AGREEMENT WITH THE SHIPS MODEL. IT
IS POSSIBLE THAT THE SYSTEM COULD WEAKEN TO A TROPICAL WAVE DURING
THE FORECAST PERIOD...AS FORECAST BY THE ECMWF...UKMET...AND GFS
MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 12/2100Z 14.3N 35.0W 30 KT
12HR VT 13/0600Z 14.1N 36.7W 35 KT
24HR VT 13/1800Z 14.1N 38.9W 35 KT
36HR VT 14/0600Z 14.2N 41.3W 40 KT
48HR VT 14/1800Z 14.6N 43.7W 45 KT
72HR VT 15/1800Z 16.0N 49.5W 50 KT
96HR VT 16/1800Z 19.0N 56.0W 50 KT
120HR VT 17/1800Z 23.0N 62.0W 45 KT
$$
FORECASTER BEVEN
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