The big story of this update is the uncertainty of the track and where TS Colin will make landfall. This is one of those cases where it may well make a very big difference on who gets the worst of this system.

Sometimes, the models just disagree; but that’s only some of the time. The big deal right now is that the centre of the storm is a bit uncertain; the circulation found this evening was well east of the previous circulation. That will tend to mean a very possible shift to the right in the landfall, and the models may not properly reflect that – just because it’s hard to get good data in so the models have good data to work on. This is not criticism of NHC; far from it. They do an amazing job. This is just one of those times where the storm is being… well… a storm.

So the first thing I want to present is not a graphic, but the forecaster discussion from the NHC for this update. A lot of times like this one, it’s one of the most important pieces of information needed for planning.

000
WTNT43 KNHC 060242
TCDAT3

TROPICAL STORM COLIN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032016
1000 PM CDT SUN JUN 05 2016

The cloud pattern of Colin remains not very well organized, and the
low-level center is impossible to discern from infrared imagery.
The imagery does show a mid-level center of rotation well to the
east of where the low-level center was last found.  Another
Hurricane Hunter mission is scheduled to investigate the storm
around 0600 UTC, and this should be very useful for locating the
center.

The current intensity is kept at 35 kt based on earlier aircraft
observations and a Dvorak data T-number from TAFB.  Strong
southwesterly shear should limit significant intensification of
Colin before it reaches Florida.  The official intensity forecast
is similar to the previous one, and close to the latest model
consensus.

Initial motion is an uncertain 010/08.  The track forecast reasoning
has not changed from the previous advisory.  Over the next day or
two, Colin should move north-northeastward to northeastward in the
flow between a mid-level over the western and northern Gulf of
Mexico and a ridge over the subtropical western Atlantic.  Later,
the cyclone should move within the mid-latitude westerlies over
the north Atlantic.  The official track forecast is similar to that
of the previous advisory and close to the latest GFS output.

It is important to emphasize that one should not focus on the exact
forecast track of this system.  Strong winds, heavy rains and
coastal flooding are likely to occur well to the east of the center.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 23.6N  87.8W   35 KT  40 MPH
 12H  06/1200Z 26.0N  86.7W   40 KT  45 MPH
 24H  07/0000Z 29.1N  84.0W   45 KT  50 MPH
 36H  07/1200Z 31.8N  79.5W   50 KT  60 MPH
 48H  08/0000Z 35.5N  72.0W   50 KT  60 MPH
 72H  09/0000Z 43.3N  54.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  10/0000Z 49.0N  39.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  11/0000Z 54.0N  33.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

So next, let’s bring in the spag. But bear in mind that the tracks presented here may mostly be too far west/north. Although TS Colin may well go west/north. The point is that the spag looks more cohesive than the reality is, so we know to take this with a larger grain of salt than normal:

Click for full graphic

Even looking at the wide area for the models’ initialization points (i.e. where they plot the storm as currently being), there’s still surprising consensus. And thus the NHC are keeping the cone on the narrow side:

click for full graphic

So on the timing — the storm is bringing showers to the western coast of Florida from Tampa down to Naples – essentially all of SW FL. This will continue and move north throughout the day on Monday. TS Colin is expected to make landfall perhaps around 8pm Monday evening, give or take – very much depending on the track. And by 7am Tuesday morning be out to sea again in the Atlantic. Orlando and Jacksonville should watch this storm closely.

Previous indications from NHC and SPC indicated that there is definitely the threat of tornadoes with this system.

Here’s the tropical-storm force wind chances forecast. Although this does look at the ensemble forecast rather than a single track, it means that while in one sense, this really is the current estimated chances these area will see these winds; bear in mind the subtlety that, for example, it’s pretty much guaranteed that where Colin makes landfall, some area (especially to the east/right) will see TS-force winds. So while no area currently has 100%, that’s in part because it depends on where the system goes. Especially with the uncertainty in the track, folks in what look like lesser-risk areas should be alert and aware. I’m just uploading the small version because the exact track shouldn’t be focused on:

(no larger version)

The last graphic for this evening will be the current wind field size, just to show that Colin is a somewhat large system. This is the estimated extent of tropical-storm force winds:

(no larger version)

Lastly, here’s the latest Public Advisory, which contains useful information about the storm’s expected impacts. Worth reading:

000
WTNT33 KNHC 060241
TCPAT3

BULLETIN
TROPICAL STORM COLIN ADVISORY NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032016
1000 PM CDT SUN JUN 05 2016

...NEW TROPICAL STORM WARNING ISSUED FOR THE ATLANTIC COAST...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...23.6N 87.8W
ABOUT 450 MI...720 KM SW OF TAMPA FLORIDA
ABOUT 455 MI...735 KM SSW OF APALACHICOLA FLORIDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...N OR 10 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The Tropical Storm Watch is changed to a Tropical Storm Warning
from Altamaha Sound Georgia to the Flagler/Volusia County Line
Florida.  A Tropical Storm Warning has been issued south of the
Flagler/Volusia County Line to Sebastian Inlet Florida.  A
Tropical Storm Watch has been issued north of Altamaha Sound Georgia
to the South Santee River South Carolina.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Indian Pass to Englewood
* Altamaha Sound to Sebastian Inlet

A Tropical Storm Watch is in effect for...
* North of Altamaha Sound to South Santee River

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within 24
hours.

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, in this case within 36 to 48 hours.

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1000 PM CDT (0300 UTC), the center of Tropical Storm Colin
was located near latitude 23.6 North, longitude 87.8 West.
Colin is moving toward the north near 9 mph (15 km/h).  A
north-northeastward to northeastward motion at a faster forward
speed is expected tonight through Monday.  On this track, the center
of Colin is forecast to approach the coast of the Florida Big Bend
area Monday afternoon or evening.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Some strengthening is forecast before Colin reaches the coast of
Florida.

The estimated minimum central pressure is 1003 mb (29.62 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL...Colin is expected to produce rainfall amounts of 3 to 5
inches with isolated maximum totals of 8 inches possible across the
northeastern Yucatan peninsula, western Cuba, western Florida,
eastern Georgia, and coastal areas of the Carolinas through
Tuesday.

STORM SURGE...The combination of a storm surge and the tide will
cause normally dry areas near the coast to be flooded by rising
waters.  The water could reach the following heights above ground if
the peak surge occurs at the time of high tide...

Indian Pass to Tampa Bay...1 to 3 ft with slightly higher amounts
possible in a few locations.
Tampa Bay south to Florida Bay...1 to 2 ft.

Localized coastal flooding and dangerous surf is possible along the
Florida East coast within the Tropical Storm Watch area.

The deepest water will occur along the immediate coast.
Surge-related flooding depends on the relative timing of the surge
and the tidal cycle, and can vary greatly over short distances.  For
information specific to your area, please see products issued by
your local National Weather Service forecast office.

WIND...Tropical storm conditions are expected to first reach the
Gulf coast within the warning area by Monday afternoon, and the
Atlantic coast within the warning area by early Tuesday.  Tropical
storm conditions are possible along the Atlantic coast within the
watch area on Tuesday.

TORNADOES...A few tornadoes are possible on Monday across portions
of Florida and far southern Georgia.


NEXT ADVISORY
-------------
Next intermediate advisory at 100 AM CDT.
Next complete advisory at 400 AM CDT.

$$
Forecaster Pasch