Tropical Storm Joaquin is currently strengthening east of the Bahamas. Joaquin is very likely going to be one of the most complex tropical cyclone forecasts in several years. I am trying to think of one like it and can't.
First, the basics.
This is as of 5pm Eastern.
SUMMARY OF 1100 PM EDT...0300 UTC...INFORMATION
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LOCATION...25.8N 71.7W
ABOUT 360 MI...580 KM E OF THE NORTHWESTERN BAHAMAS
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...WSW OR 240 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...988 MB...29.18 INCHES
WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:
The government of the Bahamas as issued a Hurricane Watch for the
Central Bahamas.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Hurricane Watch is in effect for...
* Central Bahamas
A Hurricane Watch means that hurricane conditions are possible
within the watch area, in this case within the next 36 to 48
hours.
Interests in the Northwest Bahamas should monitor the progress of
Joaquin. Additional watches or warnings may be required early
Wednesday.
For storm information specific to your area, please monitor
products issued by your national meteorological service.
DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 PM EDT (0300 UTC), the center of Tropical Storm Joaquin was
located near latitude 25.8 North, longitude 71.7 West. Joaquin is
moving toward the west-southwest near 5 mph (7 km/h) and this
general motion is expected to continue for the next couple of days.
On the forecast track, the center of Joaquin is expected to move
near or over portions of the central Bahamas Wednesday night or
Thursday.
Maximum sustained winds have increased to near 70 mph (110 km/h)
with higher gusts. Additional strengthening is expected during the
next 48 hours, and Joaquin is forecast to become a hurricane later
tonight or Wednesday.
Tropical-storm-force winds extend outward up to 125 miles (205 km),
mainly to the east of the center.
The estimated minimum central pressure is 988 mb (29.18 inches).
HAZARDS AFFECTING LAND
----------------------
WIND: Tropical storm conditions could reach portions of the Central
Bahamas by Wednesday night, with hurricane conditions possible by
late Wednesday night or early Thursday.
RAINFALL: Joaquin is expected to produce 4 to 8 inches of rain with
isolated maximum amounts of 12 inches possible over San Salvador and
Rum Cay through Thursday morning. Rainfall amounts of 3 to 5 inches
are possible over the remainder of the Central Bahamas through
Thursday morning, with 1 to 2 inches expected over the Northwest and
Southeast Bahamas.
SURF: Swells generated by Joaquin will affect portions of the
Bahamas during the next few days. These swells are likely to cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.
NEXT ADVISORY
-------------
Next intermediate advisory at 200 AM EDT.
Next complete advisory at 500 AM EDT.
Here is the 11 PM forecast discussion.
The cloud pattern of Joaquin has continued to become better
organized this evening. The low-level center is located within the
northwestern portion of the deep convection and the outflow has
continued to expand over the northern semicircle, which suggests
that the shear continues to decrease. The latest satellite
intensity estimates from TAFB and SAB are T3.5 or 55 kt on the
Dvorak scale. Based on the earlier reconnaissance aircraft data and
the continued increase in organization this evening, the initial
wind speed has been raised to 60 kt. Joaquin is forecast to be over
warm water and in an increasingly favorable upper-level wind pattern
during the next day or so. These conditions favor intensification
and the NHC forecast calls for Joaquin to become a hurricane within
the next 12 hours. The upper-level winds are shown by the global
models to become quite conducive for strengthening by 36 hours as an
upper-level anticyclone builds over the system, and additional
strengthening is anticipated. The new NHC forecast is a bit
higher than the previous advisory, and is close to the IVCN
intensity consensus aid. It should be noted, that the UKMET, GFS,
and ECMWF models all significantly deepen Joaquin during the next
few days, and the NHC forecast could be somewhat conservative.
Joaquin is moving west-southwestward at about 5 kt. This general
motion is forecast to continue during the next 24-36 hours while the
cyclone remains to the southwest of a weak mid-level ridge. During
this time, the center of Joaquin is forecast to move near or over
portions of the Central Bahamas. After 48 hours, a deepening mid-
to upper-level trough over the southeastern United States is
expected to cause a turn toward the north or north-northeast with an
increase in forward speed. There remains large spread in the
guidance at days 4 and 5, with the ECMWF showing a northeastward
motion toward Bermuda. Meanwhile, the 18Z GFS shifted significantly
westward and is close to the UKMET and HWRF, which are along the
western edge of the guidance envelope. The NHC track has been
shifted westward, but it is not as far west as the multi-model
consensus. The new track is fairly close to the ECMWF-Ensemble Mean.
The government of the Bahamas has issued a Hurricane Watch for the
Central Bahamas. Additional watches or warnings may be required
early Wednesday.
At this time it is very hard to gauge the long-range potential
impacts of Joaquin in the United States. The environmental steering
currents are complex and are not being handled in a consistent
manner by the forecast models. A wide range of outcomes are
possible and it is simply too soon to say what impacts, if any,
Joaquin will have on the United States.
This is a very low confidence forecast.
Models
Weather weenies love models and they love spaghetti. I'm not referring to Tyra Banks or pasta here.
This is the GFS model ensemble, courtesy of Weather Underground. This model (18z) ran this afternoon and was complete at 8pm EDT. You can quickly see why Joaquin is a concern.
Since Sunday, many models have looked similar to this: a storm that slides west, then southwest, before moving north northeast before making a northwest hook into the East Coast, anywhere from Cape Hatteras to Portland, ME. If this sounds familiar, it's because this is sort of what happened with Hurricane Sandy in 2012.
(you might notice the NAM is set for 2pm. It's because processing Joaquin and inputs from sea surface temps, among other things, actually broke the 18z NAM.)
Some of the scarier 18z model runs, namely the GFDL and the HWRF, which you might just see on your local news in 20 minutes if you live in Norfolk, Washington DC, Baltimore, Philadelphia, New York City, or Boston, take a fairly significant hurricane into Norfolk (HWRF) and then up the Chesapeake, New Jersey (GFS) and then lingering for days raining itself out, or into Long Island (GFDL) from the east-southeast and not the south, a track that I'd have to do some deep digging for to see if it's occurred within the last 300 years. Both the GFDL and the HWRF have been consistent for the last couple days. When I see that, I tend to pay a bit more attention to what they're trying to tell me.
What Might Make This Turn North Then Northwest?
If you live in the east you might have noticed it's raining.
It's raining a lot.
No, this isn't Joaquin. But it is related to a different tropical system (one that never organized enough to get a name) and a cold front, also known as a trough. This trough will ensure Joaquin doesn't head for Miami--it will definitely pick it up. However this trough, currently soaking the East with flooding rainfalls, will stall just along the coast. It is stuck because of a high pressure system forecasted to build over Newfoundland.
Now that would force the storm north, and then perhaps northeast. This is not unusual for hurricanes along the east coast north of Hatteras, even this late into September. What would force the storm to turn northwest is that the trough would then amplify---orient itself southeast to northwest. This is called
negative tilt. The trough is present, the blocking high is present, but the feature that is supposed to make the trough tilt is not.
That's not to mention the remnants of Tropical Storm Ida, currently in the Central Atlantic, which may interact in ways I don't know yet.
What to do?
At the time of this writing the megalopolis is not in the forecast cone but if you live in this region you might as well act as if you are, for now. Anything can happen---there's still a chance the trough does not "tilt" and Joaquin gives us a scary day and then rockets out to sea, bothering shipping. But there's a chance that this could be a hurricane strike on the US East Coast anywhere from Norfolk to Boston, four days from the time of this writing.
I don't have to tell y'all how to prepare--there are more than enough "hazard-minded" folk that we've been telling you how to do that for years. Now's the time to review your hurricane plans if you have one and build one if you don't.
I will have an update sometime on Thursday, and if needed will ask for someone to volunteer to begin the mothership on Friday evening. Impacts, if they happen, begin Saturday.
(UPDATED for 11PM Advisory--Hurricane watches are in effect for the Central Bahamas. This means there will be updates every 3 hours until the storm is no longer a threat. I also must note that while skill in forecasting intensity remains elusive, Joaquin tomorrow will slowly crawl southwest over some of the warmest waters in the Atlantic Ocean. If it gets its act together and conditions become conducive for it, this could be a seriously significant hurricane.)