TROPICAL STORM FORMATION: FRED, INVEST 91L
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*NOTE: In the TROPICAL STORM FORMATION line above, probabilities are for during the next 5 day period. My personal probability will be listed as either NONE, MONITORING or PROBABLE. This does not necessarily mean something will develop, but that certain forecast conditions are likely to be present, favoring development. Once NHC products become available, then the appropriate probability and percentage will be used.
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Current Storm Total for 2015:
TOTAL STORMS: 6
INTENSE HURRICANES: 1
U.S. LANDFALLS: 2
StormW’s Seasonal Forecast:
TOTAL STORMS: 8
INTENSE HURRICANES: 1
Good day everyone!
Tropical Storm FRED, as of the 11:00 a.m. advisory from the NHC in Miami, has been downgraded to a Tropical Depression. The following information was available on the depression at 11:00 a.m. EDT:
FRED has been undergoing wind shear once again, and the LLC has been exposed to the west of the convection. Based on the current wind shear forecast map from the GFS, I tend to agree with the NHC intensity forecast in the 11:00 a.m. Forecast Discussion. The shear forecast does indicate upper level winds in the projected path of the depression, could become favorable again within 72 hours, with an upper level anticyclone once again developing.
NHC FORECAST DISCUSSION (WITH INTENSITY FORECAST)
Based on my analysis of the current forecast steering layers maps, I concur with the NHC forecast track, which lies in agreement with the dynamic model guidance, which is tightly clustered. This will be my last post on FRED.
Elsewhere, INVEST 91L was designated yesterday as it exited the west African coast. Based on the 12Z ATCF FTP information, the following was available on the disturbance:
Location: 11.2°N 19.5°W
Moving: W at 15-20 mph
Min pressure: 1009 mb / 29.80 in
Max sustained: 30 mph
The disturbance has become slowly better organized during the past few hours. Based on my analysis of the current wind shear product from CIMSS, upper level winds were favorable for further slow development of this disturbance. Analysis of the wind shear forecast products from FSU and PENN State (GFS and CMC modeling), upper level winds are forecast to remain pretty much favorable for at least the next 96 hours, with the premise of an upper level anticyclone being maintained over the disturbance should it continue it’s current motion for the next 72-96 hours. The NHC in the 2:00 p.m. EDT Tropical Weather Outlook designated a HIGH (70%) probability of cyclone formation during the next 5 days
NHC GRAPHICAL TROPICAL WEATHER OUTLOOK
GFS 200 MB STREAMLINE FORECAST (INDICATING UPPER WIND PATTERN)
Albeit, based on water vapor floater imagery, it appears 91L has had a little bout with dry air, based on the forecast shear pattern, warm SST’s, and high TPW surrounding the system, I do believe the disturbance should be able to eventually mix out the drier air. Kind of not unlike what we saw with Erika.
INVEST 91L TPW IMAGERY
Based on the combination of all these parameters, I do believe further slow development should occur, with possible development of a Tropical Depression within the next 24-36 hours, should this organization continue. Convection has been noted flaring, just north of the center. Some slight banding features appear to be trying to develop, mainly south of the center, as based on upper level satellite derived winds, this is where the strongest outflow channel is at the moment. It is too early to tell how strong this disturbance may become. Based on analysis of the 12Z AMSU and WINDSAT data, 91L did not have a closed LLC at the time. The 12Z Intensity Guidance does bring this to tropical storm status within 4 days, based on both the majority, and the more accurate modeling. However, THIS IS TO BE CONSIDERED PRELIMINARY, as early runs of these models, when a system does not have a closed LLC, are not to be deemed as accurate.
ATCF 12Z 91L INTENSITY GUIDANCE
The disturbance is currently moving in a westerly fashion, or just north of due west, based on the ATCF FTP information, satellite loop imagery, and current shallow layer steering.
CURRENT STEERING LAYER MAP
Based on my analysis of the current run of the forecast steering layers maps, valid for 00Z this evening, I expect this motion to continue during the next 72 hours, with maybe more of a bend to due west thereafter, as the subtropical ridge expands westward and strengthens somewhat on it’s extreme southern periphery. This tends to coincide with the ATCF 12Z Dynamic Model guidance, in which I am leaning toward the TVCN-TVCC consensus models. Again, this should also be considered PRELIMINARY, as strength of the system will determine which layer the system is steered by, and should also be considered PRELIMINARY, as the models currently have no LLC to track.
I will continue to monitor this disturbance for any significant changes to strength and track during the next 72 hours.
I am also curious in another tropical wave over the African continent. Right now, the CMC model is the only one indicating development of this. The wave in question is circled in yellow.
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