Still watching for a potential early-season Atlantic subtropical storm
The latest 00Z and 12Z runs of the GFS, UKMET, NOGAPS, and ECMWF global dynamical computer models continue to indicate the possibility of an early season subtropical storm forming in the Gulf of Mexico 3 - 7 days from now. A modest area of low shear air is expected to open up between the polar jet stream to the north and the subtropical jet stream to the south, between Cuba and the northern Gulf of Mexico. The models have not been consistent with the timing or the size of this low shear area, and I wouldn't be surprised to see them back off again from this forecast with Sunday's set of runs. Nevertheless, I'll call once again for a 10% chance of development of a subtropical depression in the eastern Gulf of Mexico, 4 - 7 days from now. There isn't much of a disturbance at present to look at--there are some scattered showers between Cuba and Jamaica, but they are under a hefty 30 knots of wind shear. These showers should gradually increase in intensity and areal coverage over the next two days, and phase space diagrams from Florida State University indicate that an extratropical low may form near the western tip of Cuba 2 - 3 days from now. The storm may then gradually transition to a subtropical or tropical system later in the week, if the shear is low enough. Even if the shear is high and the storm remains extratropical, it could be a substantial rain-maker where it comes ashore. The models target the northern Gulf Coast between Louisiana and the Florida Panhandle as the most likely landfall location, but it is too early to place any confidence in this track.
There is also about a 10% chance a subtropical storm may form in the mid-Atlantic a few hundred miles east of Bermuda. There, a large upper-level cold low has cut off from the jet stream, and it may spin in place long enough over the next week to develop a warm core and be classified as a subtropical storm. It is unlikely that a subtropical storm forming that far out in the Atlantic this early in the year would pose a threat to any land areas, with the possible exception of Bermuda.
Climatology of early-season Atlantic tropical cyclones
Tropical storms are uncommon in the Atlantic before June 1, with only 26 named storms on record between 1851 - 2008. Five of these have made it to hurricane strength, and only one--Hurricane Able of 1951--made it to major hurricane status. Last year's Tropical Storm Arthur may be the deadliest May tropical cyclone on record. Though only a 40 mph tropical storm at landfall, Arthur killed five people in Belize and caused $78 million in damage. Three early-season storms have brought hurricane-force winds to land. The March 1908 hurricane swept through the northern Lesser Antilles Islands as a Category 1 or 2 hurricane, destroying at least 24 boats and causing damage to buildings on St. Bartholomew. Hurricane Able of 1951 brought sustained winds of 90 - 95 mph to the northern Bahama Islands, but caused little damage. Hurricane 2 of May 1908 hit North Carolina's Outer Banks as a Category 1 hurricane, but also caused little damage.
Figure 1. Tracking map for the earliest hurricane to make landfall, the March 1908 hurricane in the northern Lesser Antilles Islands.
List of all early season (formed in January - May) Atlantic named storms
May 31, 2008: Tropical Storm Arthur
May 6, 2007: Subtropical Storm Andrea
April 18, 2003: Tropical Storm Ana
April 21, 1992: Subtropical Storm 1
May 6, 1981: Tropical Storm Arlene
January 18, 1978: Subtropical Storm 1
May 21, 1976: Subtropical Storm 1
May 23, 1972: Subtropical Storm Alpha
May 17, 1970: Hurricane Alma (Category 1)
May 28, 1959: Tropical Storm Arlene
February 2, 1953: Tropical Storm Alice
May 25, 1952: Tropical Storm 1
May 15, 1951: Hurricane Able (Category 3)
May 22, 1948: Tropical Storm 1
May 19, 1940: Tropical Storm 1
May 27, 1934: Tropical Storm 1
May 14, 1933: Tropical Storm 1
May 5, 1932: Tropical Storm 1
May 13, 1916: Tropical Storm 1
May 24, 1908: Hurricane 2 (Category 1)
March 6, 1908: Hurricane 1 (Category 2)
May 27, 1890: Tropical Storm 1
May 16, 1889: Hurricane 1 (Category 1)
May 17, 1887: Tropical Storm 2
May 15, 1887: Tropical Storm 1
May 30, 1865: Tropical Storm 1
I'll have an update Sunday.
Jeff Masters
Reader Comments
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-- EMC Cyclogenesis Tracking Page --
Model Cycle: 2009051700
North America: Model Tracks for Mid-Latitude Cyclones
Multi-Model
CMC 00Z
Will that help the system develop?
Based on my obs of satellite img, I think the 00ZGFS and the 00ZUKMET have a good solution. This trough coming down is rather strong for May. I think the CMC is underestimating this trough. "Correction" Not picking up on the ULL in the straights.
The now visual ULL is why I think the GFS and UKMET are doing well with all of this. The surface low will follow the counterclockwise flow of the ULL and get kicked out further east.
The low shear environment is starting to materialize with our Cuban Project, we'll see. Seems to be organizing in the face of hardship, hate to see what it does if it finds a sweet spot, models have been gun hoe.
i did my first update today....Link
Did you look at My own model that i put together....
No, I didn't see it on there, where is it?
I've tracked the discussion on this page, and I see that there is a possible invest near Cuba and/or in the mid-Atlantic. I give 20~40% chance of it each forming. How about you guys?
Are a low developing under the deep convection close to Cuba? Too soon to know it perhaps.
"LONG TERM (TUE NIGHT-SUN)...THERE CONTINUES TO BE GOOD AGREEMENT
THAT A BROAD AREA OF SURFACE LOW PRESSURE OVER THE NWRN CARIBBEAN
WILL DRIFT NWWD WITH TIME INTO THE CNTRL/ERN GOMEX UNDER A MID/UPPER
CLOSED LOW OVER THE ERN GOMEX. A LARGE SPRAWLING AREA OF LOWER
HEIGHTS/PRESSURES IS FCST BY ALL OF THE MODELS...WITH THE 00Z GFS
SLIGHTLY DEEPER/FURTHER NORTH WITH ITS LOW CENTER THAN THE
ECMWF/UKMET/CANADIAN MODELS. BASED ON THE AVAILABLE MODEL
TRENDS...WILL COMPROMISE BETWEEN THE 12Z ECMWF AND 00Z GFS
SOLUTIONS. THIS SYSTEM WILL HAVE SEVERAL IMPLICATIONS ON THE
EXTENDED FCST. TIGHTENING PRESSURE GRADIENT NORTH AND EAST OF LOW`S
FCST TRACK WILL INCREASE SURFACE WINDS TO SMALL CRAFT ADVISORY
LEVELS...WITH GALE FORCE WINDS A DISTINCT POSSIBILITY. FOR
NOW...WILL CAP SUSTAINED WINDS AT 30 KT AND GUSTS AT 35 KT EARLY IN
THE EXTENDED PERIOD. THESE WIND CAPS MAY NEED TO BE RAISED BY LATER
SHIFTS AS CONFIDENCE INCREASES. AS THE GULF LOW PRESSURE SYSTEM
TRACKS TO THE NW...E-SE FLOW WILL DRAW ATLANTIC AND GOMEX MOISTURE
INTO THE REGION. THE RESULT WILL BE INCREASING POPS FOR THE WED-FRI
TIME FRAME. ALSO...THIS SYSTEM HAS THE POTENTIAL TO ACQUIRE
SUBTROPICAL CHARACTERISTICS OVER THE CNTRL/ERN GOMEX DURING THIS
TIME...AND WILL BE MONITORED CLOSELY DURING THE NEXT SEVERAL DAYS."
TO SAY THE LEAST AS MODELS IN AGREEMENT ON A CUTOFF LOW SETTLING
INTO THE EASTERN GULF. MOISTURE AND INSTABILITY ON THE EAST SIDE OF
THE LOW WILL PROVIDE GOOD RAIN CHANCES...BUT EXACTLY WHERE WILL THE
LOW SETTLE DOWN? NAM/GFS/ECMWF ALL HAVE A SURFACE REFLECTION OF THIS
LOW SOMEWHERE ACROSS THE SOUTHERN HALF OF THE STATE TUESDAY NIGHT.
CUTOFF LOWS TEND TO SIT IN PLACE FOR SOME TIME...SO THIS ONE WILL
DOMINATE OUR WEATHER LIKELY FOR THE ENTIRE LONG TERM PERIOD. GIVEN
MODEL CONSENSUS THAT IT WILL STAY TO OUR WEST WILL LEAN TOWARD THE
ABOVE NORMAL SIDE FOR POPS AND KEEP AT LEAST CHANCE SHOWERS IN FOR
EACH PERIOD. WILL NOT GO AS HIGH ON POPS AS THE GUIDANCE THROUGH
THURSDAY...THEN WILL GO CLOSE TO FOR FRIDAY AND SATURDAY GIVEN THE
BEND BACK TOWARD CLIMATOLOGY.
WITH THE INCREASE IN RAIN CHANCES...EXPECT TEMPERATURES TO BE OR
BELOW NORMAL WHEREAS MORNING LOWS WILL BE ABOVE.
Subtropical Sandwich Anyone?
It will be updated should any new information becomes available.
Mornin' Ike
Ah...first sip of freshly brewed coffee...
6Z NAM looks close to that 00Z ECMWF.
Looks like an STS is likely.
67*F in Macon, Ga this morning, 98% humidity
Nice half inch of rain last night, more on the way
Anyone else having trouble with the Nexrad radar? Regional radar won't do a loop anymore.
"LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)GUIDANCE AGREES WITH THE
SYSTEM OVER THE GULF MEANDERING NORTHWARD. THE ECMWF`S SOLUTION OF
THE SURFACE LOW MOVING OVER THE FA 24-36HRS SLOWER THEN THE GFS
CONTINUES. BOTH ARE FASTER THAN YESTERDAY`S 00Z GUIDANCE...WITH HE
GFS ADVERTISING THE SURFACE LOW MOVING OVER THE NW FL PANHANDLE GULF
COAST THURSDAY NIGHT...THE ECMWF NOW SATURDAY MORN. THE ENSEMBLE MEAN
CONTINUES TO STICK WITH THE OP GFS SOLUTION...ALTHOUGH A BIT
SLOWER...SO HAVE WENT THAT DIRECTION.
HAVE LITTLE CONCERN WITH THIS SYSTEM BECOMING THE FIRST TROPICAL
STORM OF THE YEAR AS FEEL THERE IS ENOUGH UPPER LEVEL SHEAR TO LIMIT
THIS."
I'm not having any problems.
"LONG TERM...
COULD BE AN INTERESTING END OF THE WEEK AND WEEKEND. GFS AND ECMWF
ARE COMING INTO AGREEMENT ON A SOLUTION WITH THE UPPER LOW
EXPECTED TO FORM OVER THE SOUTHEAST GULF OF MEXICO. GENERAL TRACK
WOULD BE FROM NEAR TAMPA AREA ON WEDNESDAY TO THE MOBILE-PENSACOLA
AREA FRIDAY...THEN OVER CENTRAL MISSISSIPPI AND ALABAMA FOR THE
WEEKEND. ECMWF IS SLIGHTLY SLOWER AND STRONGER...BUT SAME GENERAL
TRACK. THIS TRACK WOULD HAVE OUR AREA ON THE `DRIER` SIDE OF THE
LOW TRACK.
WE WILL BEGIN TO SEE CLOUDS INCREASE WEDNESDAY WITH CHANCES FOR
PRECIPITATION RETURNING THURSDAY. FOR NOW...WILL KEEP 12 HOUR POPS
IN THE CHANCE RANGE FOR THURSDAY AND BEYOND UNTIL TIMING AND STRENGTH
IS A LITTLE BETTER DEFINED. MAIN CONCERNS WILL BE POTENTIAL FOR
VERY HEAVY RAIN...ESPECIALLY AROUND FRIDAY AND SATURDAY.
WILL GO GENERALLY CLOSE TO THE MEX GUIDANCE FOR THE EXTENDED PERIOD.
GFS SOLUTION IS DRIVING THE FORECAST FOR THE END OF THE WEEK."
72 hour TAFB forecast
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
445 AM EDT SUN MAY 17 2009
ATLC AND GULF OF MEXICO...
FORECAST DEVELOPS A SURFACE LOW S OF CUBA TUE AND LIFTS IT
SLOWLY NORTH TOWARD THE FL KEYS THROUGH TUE NIGHT AND THEN TURNS
THE SYSTEM MORE NW INTO THE GULF OF MEXICO. AS PER COORDINATION
WITH HPC AND MFL...SLOWED DOWN THE NORTHERLY PROGRESS OF THE 00Z
GFS. THE FORECAST RELIES ON A 00Z GFS/ECMWF BLEND. CONFIDENCE IN
THE GFS DECREASES SIGNIFICANTLY TUE ONWARD AS THE 00Z CONTINUES
TO OVER-AMPLIFY THE VORTICITY ON THE EASTERN SIDE OF THE MID
LEVEL LOW...DRAGGING THE LOW TRACK EASTWARD. HOWEVER...THERE IS
SOME CONCERN THAT THE GFS MAY BE RIGHT FOR THE WRONG REASONS AS
THE 00Z UKMET HAS TRENDED MORE EASTERLY WITH THE LOW TRACK AFTER
THE LOW INCORPORATES THE MID LEVEL VORTICITY FROM THE DEEP LAYER
TROUGH EXPECTED TO PASS NORTH OF THE SYSTEM MON. FOR NOW...WILL
SLOWLY TREND TOWARD A MORE EASTERLY TRACK INTO THE GULF OF
MEXICO TUE-THU...WITH THE STRONGEST WINDS IN THE SW N ATLC N OF
THE BAHAMAS ON THE NORTHERN SIDE OF THE WARM FRONT AND IN THE
GULF IN THE NW QUADRANT OF THE LOW WED AND EXPANDING TO N
SEMICIRCLE THU. MODELS AGREE ON MOVING THE LOW NW INTO THE
CENTRAL GULF BY THE END OF THE PERIOD AS THE RIDGE TO ITS N
PASSES E FROM THE TN VALLEY WED AND OFF THE MID ATLC COAST THU.
Brings it a little closer to the other models.
out in the GOM, east of 90W.
hello, long time no see.
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