TROPICAL CYCLONE FORMATION: T.S. IAN / T.S. JULIA / T.D. TWELVE
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 10
MAJOR HURRICANES: 1
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 13-15
INTENSE HURRICANES: 3-4
Good day everyone!
A quick note…while I was out, INVEST 95L was upgraded to Tropical Depression TWELVE. Since information has changed on Julia and what is now TD 12, I am reflecting changes in the forecast from this morning.
INVEST 93L was upgraded to Tropical Storm Julia yesterday evening. Based on satellite loop imagery last night, it appeared the center was close enough to the coast, albeit somewhat inland, and with banding features noted, along with heavy convection right near the eastern edge of the LLC, the NHC made the upgrade, based on the organization of the system and tropical structure. As of the 11:00 a.m. advisory, the following was available on Julia:
11:00 AM EDT Wed Sep 14
Location: 31.4°N 81.3°W
Moving: NNE at 6 mph
Min pressure: 1011 mb / 29.85 in
Max sustained: 40 mph
Julia is still producing thunderstorm activity, and banding, east of the circulation center. This separation of the convection from the LLC is due to around 20 kts of westerly shear. Upper level winds are currently forecast to remain non conducive for any further development. The one strange thing is, albeit it did not come as a total surprise, is that Julia developed over land. If you remember, Florida being so flat and close to sea level, doesn’t really provide that much frictional effect. Katrina, if you remember, crossed across the Everglades, and as she did, believe it or not, she became slowly organized. Given that the forecast track is toward the north, Julia should remain over land, and should begin to dissipate during the next 24 hours.
Tropical Storm force gusts have been reported mainly offshore and along the coastal areas. Residents along the NE FL. coastal areas, and coastal GA / SC. should monitor the local NWS statements for the threat of heavy rainfall, localized flooding, and possible tornadoes.
From the NHC advisory:
HAZARDS AFFECTING LAND
WIND: Wind gusts to tropical storm force are possible along portions of the coasts of Georgia and southern South Carolina this morning.
RAINFALL: Julia is expected to produce 3 to 6 inches of rain near the Georgia and South Carolina coastlines through Friday afternoon. Isolated totals of 10 inches are possible. This rainfall could lead to flash flooding. Flooding may be further compounded with persistent strong onshore flow reducing river and stream discharges. Additional rainfall amounts of 1 to 2 inches are possible across northeast Florida today.
TORNADOES: An isolated tornado is possible across coastal Georgia and southern South Carolina today.
NWS LOCAL STATEMENTS
Elsewhere, Tropical Storm Ian is now moving north in the Atlantic, and during the next 24 hours, should begin to move toward the NNE, then NE, as an approaching trof should begin to re-curve the storm. I’m not touching too much on this, as it should not pose a threat to land. The storm is very poorly organized, as it has been since it was designated. Wind shear is forecast to relax briefly, and may allow for some organization and slight strengthening, before conditions become non conducive.
Elsewhere, Tropical Depression TWELVE continues to become slowly organized. Satellite loop imagery indicates convection has become a little more concentrated near the LLC, and some banding features are noted.
Based on the NHC 11:00 a.m. advisory, the following was available on T.D. TWELVE:
11:00 AM AST Wed Sep 14
Location: 17.0°N 25.0°W
Moving: WNW at 14 mph
Min pressure: 1009 mb / 29.80 in
Max sustained: 35 mph
Analysis of the current wind shear product from CIMSS indicates a small upper level anticyclone over T.D TWELVE, and the recent outflow pattern has improved since this mornings analysis, based on the CIMSS upper level winds product
Based on my analysis of the current wind shear forecast from the GFS and ECMWF, upper level winds (200 mb streamline pattern), is forecast to remain favorable, with the upper level anticyclone forecast to remain with the system, based on current track thinking. Global models indicate that wind shear values may increase in about 48 hours to marginal levels, however this seems not to correlate with the forecast pattern. Based on this, using a combination of both factors, I believe the depression will continue to slowly organize during the next 24-36 hours with possible weakening based on the shear values forecast, and the depression being over SST’s of 26C . In fact, I concur with the NHC at this time with the intensity forecast. Models are diverging on the upper level winds forecast, however based on the ECMWF wind shear / 200 mb streamline pattern, if the depression attains Tropical Storm status and possibly weakens after the 24 hour period as shown, the system could regain strength back to a Tropical Storm. Based on the forecast pattern, I have to concur with the 12Z intensity guidance at the moment, to which by 120 hours, we have a mid-grade Tropical Storm.
The disturbance is moving toward the WNW near 14 mph, and I expect this motion to continue during the next 24-36 hours, before a turn toward the west occurs. The disturbance is heading for a slight weakness in the ridge off the the NE. In the mentioned time frame however, the ridge begins to slowly build west, with the ridge becoming oriented almost directly north of the system. This is reflected in the current forecast steering maps, and inline with current dynamic guidance and GFS / ECMWF Ensemble members. Right now, as I always state, take this guidance should be considered preliminary, based on the fact the models keep changing the 500 mb pattern …however model consensus seems to agree on this scenario, and has for the past 48 hours. After around days 4-5 in the forecast period, a large break, or weakness in the ridge is forecast, in which the global models are in good agreement of this system taking a more NW path, then northward. This will all hinge on whether or not the ridge forecast over the eastern U.S. area can build in over it, or if it weakens as shown. You’ll note the break and weakness in the ridge in the following combines ECMWF-GFS 500 mb anomaly map.
I’ll continue to monitor this system for any significant changes over the next few days, and I should have another update lat Sunday afternoon / early evening.
Elsewhere, the NHC indicates another wave will exit Africa by the weekend, and designates a 40% probability over the next 5 days of tropical cyclone formation. Based on forecast steering however, it appears this one will make an immediate re-curve.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days.
Have a blessed day!
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS