Ana and TD 3 take aim at the Lesser Antilles
Tropical Storm Ana was born this morning, when the remnants of Tropical Depression Two made a comeback and organized into the first tropical storm of the 2009 Atlantic hurricane season. Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 1992. The two storms have some similarities, as Andrew formed in the same part of the ocean, and also struggled in its early days with high wind shear and dry air. Let's hope the similarities end there.
Ana is struggling this afternoon. After an modest burst of heavy thunderstorm activity prompted NHC to upgrade Ana to a tropical storm early this morning, Ana has run into strong upper-level winds from the west that are creating high wind shear. This shear was not forecast, and it is not clear how long it will last. The shear has acted to drive dry air into the core of Ana, destroying almost all of Ana's heavy thunderstorms. The low-level center of the storm is now exposed to view, something that often foreshadows the death of a storm. It is possible the shear will destroy Ana, and several models (the GFS and ECMWF) forecast this may be the case. However, the shear forecast calls for shear to drop into the low range, 5 - 10 knots, tonight through Tuesday. If the shear does drop as forecast, Ana should be able to moisten the atmosphere around it sufficiently to protest itself from the dry Saharan air that surrounds it (Figure 1). SSTs are 27°C today, and will increase to 28°C by Sunday. By the time Ana moves into the Bahamas, total ocean heat content rises steeply (Figure 2), and rapid intensification of Ana is possible, if the shear and dry air haven't disrupted the storm. The intensity forecast models, for the most part, predict a steady intensification of Ana to the threshold of hurricane strength five days from now. The HWRF model is on the strong side, predicting a Category 2 hurricane. The GFDL predicts a weak tropical storm five days from now, but that is because the model has Ana passing over the rugged terrain of Hispaniola, something the other models do not predict. In summary, the intensity forecast for Ana has higher than usual uncertainty, and I give equal chances that the storm will be a hurricane--or non-existent--four days from now.
Figure 1. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the north of Tropical Depression Three. Image credit: NOAA/SSD
Tropical Depression Three forms, could be Bill later today
QuikSCAT data from this morning and satellite loops revealed that the tropical wave (90L) in the middle Atlantic has finally developed a well developed surface circulation and can be classified as Tropical Depression Three. Recent satellite imagery suggests that TD 3 may already be Tropical Storm Bill. Water vapor imagery (Figure 1) shows that TD 3's center consolidated a few hundred miles south of the dry air of the Saharan Air Layer (SAL). Thus, the storm should not be affected by dry air and dust as much as Ana has been. Ana may also act to moisten the atmosphere in front of TD 3, helping protect the storm from the SAL as it edges farther north over the the three days.
Figure 2. Heat content of the ocean, in kJ per square cm. Oceanic heat content steadily increases for Ana and TD 3 as they approach the Lesser Antilles Islands. Oceanic heat content levels of 90 kJ per square cm are frequently associated with rapid intensification of hurricanes. Image credit: University of Miami.
Wind shear is moderate, 15 knots, but is forecast to fall to 10 - 15 knots on days 2 - 5. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow TD 3 to intensify steadily, and I expect the storm will be at hurricane strength by Wednesday, when it will be near the northern Lesser Antilles Islands. Most of our reliable intensity models strengthen TD 3 into a hurricane by Wednesday. Oceanic heat content (Figure 2) increases sharply just before the islands, so TD 3 could be intensifying rapidly as it moves through or just north of the Lesser Antilles on Thursday. TD 3 consolidated farther south than expected, so the track models calling for a more northerly path were probably incorrect. In particular, the ECMWF model, which had TD 3 turning sharply northwestward and missing the Lesser Antilles Islands, was probably much too far to the north in this morning's 00Z run. TD 3 will probably pass very close to the northern Lesser Antilles islands on Wednesday and Thursday.
I'll have an update Sunday.
Jeff Masters
Reader Comments
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I hate to say it...but this is why they always say - be prepared by June 1 - you NEVER know what will happen. I'm just afraid too many don't heed the warning
Wow.. Seriously? It's not even close to Hurricane strength, and it is definitely not a Tropical Storm at the moment. It would be lucky to be named a Depression as of now, given the lack of outflow and the latest QuikSCAT which shows no closed surface circulation, or any lower level circulation for that matter. This is still a wave interactive with a middle and upper-level trough. However, with that said, it is in a steamy Gulf of Mexico where any tropical system can intensify quite rapidly, and it does look likely (Given 10kt shear, 86 degree SST's, decent OHC nearby) that this will intensify today and become a Depression at some point today, and possibly a Storm.
I see a storm soon, but not a Hurricane. We need to temper those forecasts a bit :)
Amen. We haven't been the same since, nobody around this part of Texas wants anything to do with anything over 20 mph. Kids still get spooked during a regular thunderstorm.
SPECIAL MARINE WARNING
GMZ853-873-160900-
/O.NEW.KTBW.MA.W.0114.090816T0711Z-090816T0900Z/
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
311 AM EDT SUN AUG 16 2009
THE NATIONAL WEATHER SERVICE IN RUSKIN HAS ISSUED A
* SPECIAL MARINE WARNING FOR...
WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 TO 60 NM OVER
GULF OF MEXICO WATERS...
COASTAL WATERS FROM ENGLEWOOD TO TARPON SPRINGS FL OUT 20 NM OVER
GULF OF MEXICO WATERS...
* UNTIL 500 AM EDT
* AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
THUNDERSTORMS...PRODUCING STRONG WINDS 34 KNOTS OR GREATER...
COVERING MOST OF THE GULF WATERS BETWEEN 15 AND 60 NM OFFSHORE
FROM ENGLEWOOD NORTH TO CLEARWATER BEACH. THESE STORMS ARE
ASSOCIATED WITH AN AREA OF LOW PRESSURE MOVING NORTHWEST THROUGH
THE EASTERN GULF. THE STORMS ARE MOVING NORTH AT 25 TO 30 KNOTS.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
MARINERS CAN EXPECT STRONG WINDS...HIGH WAVES...DANGEROUS
LIGHTNING...AND HEAVY RAINS. WATERSPOUTS WILL ALSO BE POSSIBLE IN
SOME OF THE HEAVIER RAIN BANDS. BOATERS SHOULD SEEK SAFE HARBOR
IMMEDIATELY.
MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SUN AUG 16 2009
MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA
AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W.
AN AREA OF LOW PRES HAS DEVELOPED OVER THE EASTERN GULF OF MEXICO
ABOUT 80 MILES SW OF TAMPA. THE LATEST NHC TROPICAL OUTLOOK SAYS
THERE IS A GOOD CHANCE THAT THIS LOW COULD DEVELOP INTO A
TROPICAL CYCLONE LATER TODAY. THE LOW IS MOVING NW 15 KT. WILL
UP THE WINDS IN THE EASTERN GULF WITH THE LOW FROM 15-20 TO
20-25 KT. WINDS INCREASE OVER THE SW GULF LATE MON AND MON NIGHT
AS THE N PORTION OF A TROPICAL WAVE MOVES ACROSS THE SOUTHERN
BAY OF CAMPECHE. WILL WAIT FOR LATEST ADVISORY ON TROPICAL
STORM ANA...AS THE PREVIOUS ADVISORY BROUGHT ANA INTO THE
STRAITS OF FLORIDA ON THU EVENING. MAY HAVE TO HEADLINE
E GULF ZONE FOR TROPICAL CONDITIONS EXPECTED.
Whatever...I didnt look.
I just posted the model data that says it up to 45.
Well, it could. Other requirements besides 39mph winds can prohibit a tropical cyclone from forming. So there could be a storm that was a TS the second it gained tropical cyclone status. Ie. Vince, Tammy 2005.
how old are you?
and they had that as a yellow scribble in the earlier (way less than 48hours ago) advisory
well stated.
What does that have to do with anything?
Look at the rotation on these feeders.
"Crazy over an invest, three in the morn"
That loop reminds me of Humberto. I think we'll see that kind of development as it moves between nnw and nw. Right now I just don't see the wnw some people are talking about. That could be because it's 3:22am and I can't sleep.
Totally understand, Im here in Clear Lake... Just the mention of the "H" word spooks everyone around here. We were loving the quiet season...lol... Should have known better
Very strange. Not unexpected though. I live in Bonita Beach and it was off-and-on sun/rain/sun. We decided to jump on the boat and go up the back bay for a quick bite to eat for a few hours in between the "bands." It was a nice day except for a few quick squall-like wind/rain moments. I figured it would pour here tonight but besides a light breeze, none of the real rain made it here. Overall, very little effect from this disturbance but looking at this radar it is quite interesting to see it go from a blob of thunderstorms to a condensed, circulating "storm" so quick.
We did have some damage though... our Royal Palm lost a frond that flew about 15 feet in a "gust." :)
And so does NRL.
1) yes, for a very long time now
2) could be, too far out to be certain & its a fighter
the tropics continue
Link please, if you wouldn't mind. Thanks
WHXX01 KWBC 160719
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0719 UTC SUN AUG 16 2009
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
TROPICAL CYCLONE FOUR (AL042009) 20090816 0600 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 0600 090816 1800 090817 0600 090817 1800
LAT LON LAT LON LAT LON LAT LON
BAMS 27.0N 83.5W 28.7N 85.0W 30.1N 86.5W 31.4N 87.7W
BAMD 27.0N 83.5W 28.4N 85.0W 29.4N 86.3W 30.2N 87.4W
BAMM 27.0N 83.5W 28.4N 85.0W 29.7N 86.4W 30.7N 87.7W
LBAR 27.0N 83.5W 28.7N 84.7W 30.6N 85.9W 32.4N 86.8W
SHIP 30KTS 36KTS 42KTS 48KTS
DSHP 30KTS 36KTS 42KTS 38KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 0600 090819 0600 090820 0600 090821 0600
LAT LON LAT LON LAT LON LAT LON
BAMS 32.5N 88.5W 34.2N 89.4W 37.5N 86.1W 42.0N 75.4W
BAMD 30.9N 88.2W 32.2N 89.0W 34.2N 86.0W 37.9N 77.8W
BAMM 31.5N 88.5W 33.0N 89.4W 35.5N 86.1W 39.7N 76.2W
LBAR 34.5N 86.7W 37.8N 81.8W 40.2N 70.4W 38.3N 64.2W
SHIP 52KTS 57KTS 58KTS 62KTS
DSHP 31KTS 27KTS 27KTS 28KTS
...INITIAL CONDITIONS...
LATCUR = 27.0N LONCUR = 83.5W DIRCUR = 330DEG SPDCUR = 13KT
LATM12 = 25.1N LONM12 = 81.9W DIRM12 = 309DEG SPDM12 = 17KT
LATM24 = 23.8N LONM24 = 79.1W
WNDCUR = 30KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1011MB OUTPRS = 1015MB OUTRAD = 90NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
Pressure has dropped 2mb in about an hour, seemingly.
Still way too early to speculate on Bill and the sys. behind it.
As for Ana, she could very well be toast. She outran all her convection, but as long as the low to mid-level circ. remains intact, she's not totally out of the game. Looking pretty bad for her though.
Just woke up to use the restroom....
Not really surprised about 91L. Looks headed close to here.
not 1, not 2 but 3 depressions in less than a week.
Watchout Ike! Lots of rain and strong TS winds possible
ATLANTIC OBJECTIVE AIDS FOR
TROPICAL CYCLONE FOUR (AL042009) 20090816 0600 UTC
td4? :/ where does it say so...
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