TROPICAL CYCLONE FORMATION: INVEST 97L (60%)/INVEST 96L (20%)
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(T. F. “Storm” Walsh III)
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CURRENT 2016 TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 4
INTENSE HURRICANES: 0
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 14-16
INTENSE HURRICANES: 3-4
Good day everyone!
This evening, we’ll begin closer to home with Tropical disturbance INVEST 97L.
INVEST 97L has improved during the day regarding convection, and a slight expanse in its moisture field. Information from CIMMS INVEST satellite information page indicates somewhat of an increase of TOT (Tropical Overshooting Tops). Some of these overshooting tops can be noted in satellite loop imagery.
The NHC in Miami has designated a MEDIUM (60%) probability for cyclone formation over the next 5 days.
2:00 PM EDT Sat Jul 30
Location: 15.0°N 54.5°W
Moving: W at 25-30 mph
Min pressure: 1009 mb/29.80 in
Max sustained: 35 mph
The disturbance is moving toward the west, to just north of west at around 25-30 mph. Based on current and forecast steering layers maps, I expect this general motion to continue during the next 66 to 72 hours, continuing to possibly gain a little more latitude (slowly), before a more westward track takes effect once again. The 18Z dynamic model guidance pretty much indicates this, with forecast steering showing more of a westward streamline flow thereafter. PLEASE BEAR IN MIND HOWEVER…with the lack of a close LLC (Low Level Circulation) in which modeling hasn’t had at this point to initialize, this scenario could change if this system becomes organized and begins to strengthen. For the short-term , the motion seems fairly straight forward. Based on forecast steering, I am not really expecting any abrupt slow down in forward speed, and the forward speed could remain Status Quo for the next few days. Forecast steering indicates there COULD be a slowing in forward speed once this approaches the Yucatan Peninsula area. A slight weakness in the ridge is indicated in the extreme NW GOMEX by that time, however at the moment, it does not appear strong enough to impart a NW motion on the system. Again (pay attention here), steering has been shown to change within 5 days time, and once again, the strength of the system will also dictate path.
As far as strength, given the current forward speed, development would be slow to occur, and I believe slower than what current intensity guidance is showing at the moment.
Based on forecast guidance, I do believe we should see an improvement in structure over the next 36-48 hours, as the disturbance will be moving into an area of 30C SST’s, and higher OHC. IF this can acquire a closed surface reflection, Then I am more apt to believe intensity forecast guidance which bring this to hurricane force in about 3 days.
The disturbance is under favorable upper level winds, with an upper level anticyclone still over the system. The current wind shear forecast indicates this feature to continue to remain in place over the next 5 days, with shear fluctuating between 5-14 knots during the period.
Based on this, I am calling for further SLOW improvement/increase in convection during the next 48-72 hours, and I will continue to monitor 97L for any significant changes, and any formation of a closed LLC.
Based on the NHC GWTO from 2:00 p.m. EDT, the NHC indicates 96L has become less organized. I did note however, that in the last few frames of satellite loop imagery, it appears 96L may be trying to pull together again.
Based on information contained in the 18Z ATCF BTK report, the following was available on INVEST 96L:
2:00 PM EDT Sat Jul 30
Location: 11.5°N 29.0°W
Moving: W at 15 mph
Min pressure: 1010 mb/29.83 in
Max sustained: 30 mph
Upper level winds are currently somewhat conducive, but not optimal for quick recovery. Wind shear may relax within the next 40 hours, however information from the RUC NOAA Tropical Cyclone Diagnosis site indicates wind shear is forecast to increase in about 54-60 hours, which would make an unfavorable environment. Based on the NHC GTWO, they have decreased the probability of cyclone formation with 96L to LOW (20%)
This disturbance has been moving toward the west at around 15 mph, after gaining some latitude yesterday, and losing latitude over the past 12 hours, as had been forecast in my previous synopsis.
Based on current and forecast steering layers maps, I expect this motion to continue for the next 72 hours or so, and is in line with the 18Z dynamic model guidance.
I will continue to monitor this disturbance to see if it can take advantage of the forecast, more favorable upper environment in 2-3 days, before wind shear once again increase.
Based on satellite loop imagery, another wave appears as if it will exit the African coast tomorrow, with another wave right behind it. The current wind shear forecast indicates upper level winds could be conducive for development of either of these. Again, wind shear can change in a very short period, so I will be re-visiting the conditions in this area over the next 4 days.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS